# Engine Will Not Cool - At Wits End!!



## QDuck (Sep 14, 2019)

I have a 1966 LeMans, 400 engine, T56 trans and 3.33 rear end gears. For more than two years I have been fighting cooling problems and thought it might be okay until a recent trip to southwest at high altitude and high temps (80-90 F).

The engine is a low compression, basically stock 400 with a mild cam. Factory headers. I have Griffin radiator rated for 700 HP. Dual SPAL fans at 3600 cfm full shroud with flaps to allow air flow at high speed. 16 psi cap. 160 thermostat. Unless the outside temp is in the 50s or below it will not run under 180. At 70F it's 180-190 around town with fans running full time. On highway it's about 200. When temp gets to 80+ it runs at 225 and in high 80s it will run hotter. It seems to run cooler or not heat up as quickly if the speed gets up to 80 mph but hotter at slower speeds. On my recent trip I had put heater on to keep temp below 225. That dropped the temp 10-20 degrees for some minutes but gradually crept up. Interestingly it did not matter if the heater fan was or not so I simply by-passed the heater so water ran through the hoses all the time. That way i could sill get AC. This does not make it run cooler but lengthens the time before it gets too high and helps it cool off faster if I slow down. I could not run at speed limit without it getting too hot. The engine runs 180-200F at idle in traffic and in stop and go traffic it still remains around 200 or less, significantly less than on open highway. 

I have done everything that anyone suggested. Some of it helped but it only helped to keep temp below 245 and higher but not to run cool. This is the second newly rebuilt engine (the first was a 455 with about 450 hp). This one now has 15000 miles and should be broken in. It's also the second radiator and the dual 14" fans replaced a single brushless fan rated at 2600 cfm. I had waterless coolant which raised the boiling point but also made it run a few degrees hotter so I'm back to distilled water and anti-freeze. There are two temperature sensors in the front of the intake. One is for the temp gauge and the other a fan switch. Both record the same temperature which seems to be accurate as far as I can tell.

Also, the engine temp rises tremendously when I shut it off. The fans will run for nearly 20 minutes shutting off at 180. The radiator water is down to 90F or less but the engine temp remains in the mid 200s If I start car temp will drop 10-15 degrees at which time I shut off and repeat. This will get temp down to 180 in 5-10 minutes. There's a high flow thermostat and I've tried 190, 180 and 160 stats. The only unusual thing is a serpentine belt system which requires a reverse rotation water pump of which a high volume version does not exist. The diverter plate has about .020 clearance.

So, some questions and ideas I've heard.

1. It seems to me that the water is not circulating through the engine as it should. 
First I think it should circulate when shut off until the thermostat closes. Is that right?
Second, the top/bottom radiator hoses are connected as they should be. The heater hose comes off the water pump and into the engine at rear of passenger side cylinder head. But, does this really matter as if the heater is off it doesn't circulate there at all.
2. Could the reverse direction water pump cause problems? I am sure others must have these same pumps but do they have problem?
3. What would be considered the maximum operating temp?
4. What about timing and idle mixture? Timing is set at 12-14 degrees BTDC with vac advance disconnected. Idle mixture is set to highest manifold vacuum at idle speed of 1000 rpm.
5. I am planning to add an additional heater core and fan for more water capacity and hopefully additional cooling. The only place where there is room to put this is in the engine compartment but with 200 degree air going over the core it probably won't cool much. There is no place to put an air duct in for fresh air from the grill without cutting holes in the radiator support. 

Please any comments or ideas as much summer travel is planned.


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## RMTZ67 (Mar 12, 2011)

Just curious....has it ever spewed over when you park and shut the engine off? Water level in the radiator should be down about 1.5 inches give or take. Others will chime in with the usual methods, I resolved myself to think, as long as mine aint boiling over/spewing out...I am good with what I have done. Temp gauge goes up 220 on occasion. All in the city. Guess every pontiac is unique or not.


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## PontiacJim (Dec 29, 2012)

*QDuck*: "the engine temp rises tremendously when I shut it off. The fans will run for nearly 20 minutes shutting off at 180. The radiator water is down to 90F or less but the engine temp remains in the mid 200s If I start car temp will drop 10-15 degrees at which time I shut off and repeat. This will get temp down to 180 in 5-10 minutes."

*PJ*: Normal happening. Each time you shut the engine off, the fans/coolant in the radiator drops temp and when you start back up, the cooler coolant circulates through the engine to pull down temps 10-15 degrees and then you shut down and repeat. * Without the water pump circulating to move coolant through the radiator for cooling, all the engine heat is transferred directly into the coolant and temp levels can soar.* One reason race/drag cars will use an electric motor/water pump system to keep coolant circulating when the engine is shut down.

*QDuck:* Since this has happened with 2 different engines, there has to be a common denominator.
"I have Griffin radiator rated for 700 HP."

*PJ*: What does that actually mean and how do they rate a radiator for 700HP? MEANINGLESS. More importantly is the size of the radiator, inlet/outlet locations, number of cores, how many cooling tubes, and what size diameter the cooling tubes are.

*QDuck:* The heater hose comes off the water pump and into the engine at rear of passenger side cylinder head.

*PJ:* So how do you connect it to the heater core on the firewall? Is it disconnected now and bypassing the heater core? You can do this and it will work, but no heat.

*QDuck:* At 70F it's 180-190 around town with fans running full time. On highway it's about 200. When temp gets to 80+ it runs at 225 and in high 80s it will run hotter.

*PJ:* Not enough cooling from the radiator - possibly air flow/radiator design/size, possibly timing issues, possibly carb issues - leaning out.

*QDuck:* What about timing and idle mixture? Timing is set at 12-14 degrees BTDC with vac advance disconnected. Idle mixture is set to highest manifold vacuum at idle speed of 1000 rpm.

*PJ:* Why is your idle at 1,000 RPM's? WAY TOO HIGH for a basically stock/mild cam engine. Stock, especially with a manual trans, about 650 RPM's -then adjust for highest vacuum. If you cannot get this, and the engine dies out below 1,000 RPM's, something is amiss - vacuum leak (also causes lean condition and hot engines), incorrect valve adjustment, bad carb, distributor/timing issues.
What is your timing specs? Total Mechnical @ "X" RPM. how much vacuum advance do you get from the advance?

*QDuck*: The only unusual thing is a serpentine belt system which requires a reverse rotation water pump of which a high volume version does not exist.

*PJ*: I would be looking here. From what I read, the casting itself may be the problem as it can somewhat block water flow by its design. The casting, IF molded like original, was not intended for reverse flow even though you can install a reverse flow impeller or one with straight blades that ar bi-rotational. You also want to have the correct pulley sizes matched to speed up water flow - especially with the AC. So if the pump is not circulating enough coolant, you would experience all the symptoms you now experience. Not saying this is it, but it could be the main issue. Not knowing your set-up, you want to have the idler pulleys and a good "wrap" of the belts around your pulleys so they are not slipping at higher engine speeds.

*PJ:* As I see it, we need more info and you may have several issues and not just a single issue - which is adding up to the hot running of the engine.


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## Jared (Apr 19, 2013)

Coolant doesn't circulate when the engine is off. Are you sure the gauge is right? Checked the radiator temp with a laser temp reader?


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## ponchonlefty (8 mo ago)

you say low compression. tell us more.ok i see you said stock compression. but is it 8.1 or 9 or more? do you have problems starting when cold or warm? maybe give us which cam you have.


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## BearGFR (Aug 25, 2008)

> *QDuck:* The heater hose comes off the water pump and into the engine at rear of passenger side cylinder head.


I believe this is backwards. The hose coming out of the rear of the passenger side head should go to the heater core. The other hose hose from the heater core goes to the water pump. I don't know if this is the cause of your problem or not, but it's worth a try. 

Bear


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## ylwgto (Oct 27, 2009)

Have you clearanced your water pump divider plate? This made a HUGE difference in my cooling.

also, if your water pump is not designed for reverse flow the impellers may be operating in the wrong direction (think ceiling fan blades in reverse…sucks air up instead of blowing down).


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## PontiacJim (Dec 29, 2012)

BearGFR said:


> I believe this is backwards. The hose coming out of the rear of the passenger side head should go to the heater core. The other hose hose from the heater core goes to the water pump. I don't know if this is the cause of your problem or not, but it's worth a try.
> 
> Bear


Nope, he stated he disconnected and jumped the hose from the timing cover outlet to the back of the passenger side head in an attempt to see if it ran cooler or if this was a problem.


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## PontiacJim (Dec 29, 2012)

ylwgto said:


> Have you clearanced your water pump divider plate? This made a HUGE difference in my cooling.
> 
> also, if your water pump is not designed for reverse flow the impellers may be operating in the wrong direction (think ceiling fan blades in reverse…sucks air up instead of blowing down).


*The OP stated *he clearanced his water pump plate "about .020" and is using a reverse flow water pump - assume a Flow Cooler having the non-directional straight impeller vanes so it can be used either way.


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## QDuck (Sep 14, 2019)

Radiator is made by Griffin. Cross-flow, 3 inches thick, 2 rows, core 2.68 in, tube 1.25 in, core dimension 21 x 19 in. Engine is 9.6:1 compression. I no longer know where I got idle speed spec from but after research I find it should indeed be much lower. I always thought 1000 rpm was too high anyway. However, this would have no affect on cooling at speed. I doubt belt slippage is an issue as the belt is nearly new, good tension and full contact on all pulleys. Yesterday was 80 degrees. Started car and let idle for 15 minutes and temp came up to 180 (160 Thermostat) soon then slowly crept to 190. 1/4 mile out of driveway was 198. On highway at 75-80 for about 10 miles got to 210. Then in 5th gear (~3000 rpm) at 75 mph for 7 miles went to 215. On deceleration ramp went to 225 and then easy driving no traffic but lots of shifting due to curvy road remained at 225 to 227. Stopped and with 1 -2 minutes temp down to 210 at idle. Drove home at 35-40 mph temp was down to 203. Measured radiator with IR thermometer. I don't rely on these much because results are dependent upon surface, color, and some other factors. Regardless, I measured radiator from front of car near the top and bottom. TL (Driver side) was 141; TR 117; BL 192; BR 184. This was quite a surprise to me as previous measurements showed a large drop in temp from top to bottom. The radiator was just professionally tested a month ago and showed no problem. I do have a large AC condenser. There are no starting problems. I live on East Coast at an elevation of 170 feet. When out west at 4000-6000 feet it would labor when trying to start with engine temp above 220. I did make an attempt to adjust idle mixture by ear to adjust for elevation. As pointed out the water diverter is properly clearanced, heater is currently bypassed and the water pump is a reverse direction pump with straight vanes. I too am suspicious of this as a contributing factor but my limited knowledge of hydrodynamics tells me it should still pump as good as a normal pump with straight vanes. Today I will lower idle and readjust timing, carb and test again. A problem is that running 10-20 miles at 80 mph on 55 mph speed limit highways is different than running 75-80 for 2-3 hours.

An aside and unrelated question: When setting timing and carb I disconnect the vacuum advance and put vacuum gauge on full manifold vacuum and set at about 12 BTDC. When the vacuum advance is reconnected the engine speed picks up. Should I drop idle back down to curb idle speed? I'll let you know what the timing values are.


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## Mine'sa66 (Oct 30, 2019)

Sure sounds to me like you have poor flow and as mentioned, I'd be looking at your pump setup.


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## LATECH (Jul 18, 2018)

PontiacJim said:


> Nope, he stated he disconnected and jumped the hose from the timing cover outlet to the back of the passenger side head in an attempt to see if it ran cooler or if this was a problem.


See there is a problem.I know that it is how it is supposed to be , but think about it. The water flowing out the heater hose from the back of the head never sees the radiator.How can it cool.?It flows back into the engine
It was built that way. Its a pontiac design that can almost be considered a flaw.
There already exists a bypass for coolant for warmup of the thermostat by the timing cover water passage, so why dump hot water into an already hot engine?

My thought was , and I have experianced the same temp issue, is that it would be better if the rear of both heads had an outlet AND that they dumped into a heater hose fitting on the radiator.I have seen chevy trucks in the 70s and 80s where the heater hose return dumps into the radiator.
To me it just makes sense


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## LATECH (Jul 18, 2018)

My though was to hook this in the top hose and hook the heater hose to it. Block the fitting at the pump. It would be simple to do.The only thing is you would have to cut the upper rad hose.
Better than hacking up a radiator to install a fitting for testing purposes 

https://www.autozone.com/cooling-he...6mX9Xt1bylr8d1uPsH8aAi4ZEALw_wcB&gclsrc=aw.ds


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## PontiacJim (Dec 29, 2012)

LATECH said:


> See there is a problem.I know that it is how it is supposed to be , but think about it. The water flowing out the heater hose from the back of the head never sees the radiator.How can it cool.?It flows back into the engine
> It was built that way. Its a pontiac design that can almost be considered a flaw.
> There already exists a bypass for coolant for warmup of the thermostat by the timing cover water passage, so why dump hot water into an already hot engine?
> 
> ...


Here is what I pulled from a post from Tom V. over on the PY Forum. I did not post word for word, nor use the entire post. I used what I needed to answer your question and changed a few things to make it easier to follow along.

The coolant from the radiator goes to the inlet at the water pump and the coolant is then pumped through the two inlets in the front of the engine block. The coolant passes from the front of the block to the rear of the block with the coldest coolant entering the front of the engine block.

As the coolant moves from the front of the block to the rear of the block, there are coolant holes in the block that match up with coolant holes in the cylinder heads. Depending of the location and size of the holes coolant from the block flows to the cylinder head.

Because there are a number of small holes in the block deck and the cylinder head surface, the coolant's flow path goes from the front of the block to the rear of the block and then from the rear of the heads to the front of the heads to where the water crossover is. The coldest coolant at the front of the block mixes with the hottest coolant from the cylinder heads and equalizes the water temp in the block and heads for all of the engine cylinders and valves.

The coolant routing for the heater is a nipple at the rear of the passenger side head. Some coolant from the passenger head (about 10 gallons/min on a typical heater core system) is diverted to the heater core. If the water pump flows on average 40 gallons per minute through each head you now lost 25% of your cooling effectiveness on the passenger head and is why the passenger side head typically runs a little hotter than the driver's head.

Some people decided to "fix" the cooling/temp difference between the heads by having adding a nipple to the rear of the driver's side head and make the coolant flow from both cylinder heads, joined by a "Y" or "T" fitting and then go to the heater core. This improved things a little bit because the heater core still flowed 10 gallons/ min of coolant, and if each head supplied an equal amount of coolant, each head was delivering 5 gallons/min going through the heater core and then back to the front of the engine for cooling. This still meant the heads were pushing a combined10 gallons/min through the heater core, but the cooling on each side head/block was more even and the engine cooled better.

Some people decided to add cooling lines coming from the rear of the heads and plumbed directly into the water cross-over and eliminating the heater which acted as a coolant flow regulator. If large diameter lines were used they may have been by-passing over 20 gallons of coolant out the back of the heads and right into the radiator through the water crossover without using any of it to pass back through the heads to the front of the engine to help in cooling the cylinder heads - the coolant flow was taking the least path of resistance, right out the rear of the heads before being used as a coolant.

You can limit the amount of coolant flowing out the back of the head going to the heater core. The nipple on the heater core is sized for a 5/8" ID hose. Using a pair of flat bill or needle nose pliers, bend the nipple inward so that the opening takes on a shape more like a square and is about 3/8" diameter across the square vs the large 5/8" opening. This reduces the coolant flow and is still enough for the heater core to do its job. There are also other "homemade" ways to reduce/restrict the ID of the heater core nipple or hose.

So, can you eliminate the coolant outlet on the passenger side head? Yes. Isn't that what a vacuum operated shut-off valve does on cars equipped with AC? (Not 100% sure on this?) Will it affect coolant temps - possibly. It's real purpose is to supply hot coolant to the heater core with the return flow going back into the water pump bypass nipple. If the back of the passenger side head outlet is routed back into the water pump bypass, I don't believe it is doing any cooling as it is being pumped right back into the front of the engine - which may or may not be mixing in hot coolant from the head into the cooler water coming in from the radiator. So my thinking is that it would be better to block the outlet off, rather than plump it back into the water pump by-pass fitting.


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## LATECH (Jul 18, 2018)

Pontiac Heater coolant outlets also have a restriction built in to keep the flow regulated as extreme flow /pressure can rupture a heater core. At least the ones I have seen do
And, they are 5/8 to the heater core and the heater core outlet is 3/4 . All in the name of pressure reduction


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## PontiacJim (Dec 29, 2012)

QDuck said:


> Radiator is made by Griffin. Cross-flow, 3 inches thick, 2 rows, core 2.68 in, tube 1.25 in, core dimension 21 x 19 in. Engine is 9.6:1 compression. I no longer know where I got idle speed spec from but after research I find it should indeed be much lower. I always thought 1000 rpm was too high anyway. However, this would have no affect on cooling at speed. I doubt belt slippage is an issue as the belt is nearly new, good tension and full contact on all pulleys. Yesterday was 80 degrees. Started car and let idle for 15 minutes and temp came up to 180 (160 Thermostat) soon then slowly crept to 190. 1/4 mile out of driveway was 198. On highway at 75-80 for about 10 miles got to 210. Then in 5th gear (~3000 rpm) at 75 mph for 7 miles went to 215. On deceleration ramp went to 225 and then easy driving no traffic but lots of shifting due to curvy road remained at 225 to 227. Stopped and with 1 -2 minutes temp down to 210 at idle. Drove home at 35-40 mph temp was down to 203. Measured radiator with IR thermometer. I don't rely on these much because results are dependent upon surface, color, and some other factors. Regardless, I measured radiator from front of car near the top and bottom. TL (Driver side) was 141; TR 117; BL 192; BR 184. This was quite a surprise to me as previous measurements showed a large drop in temp from top to bottom. The radiator was just professionally tested a month ago and showed no problem. I do have a large AC condenser. There are no starting problems. I live on East Coast at an elevation of 170 feet. When out west at 4000-6000 feet it would labor when trying to start with engine temp above 220. I did make an attempt to adjust idle mixture by ear to adjust for elevation. As pointed out the water diverter is properly clearanced, heater is currently bypassed and the water pump is a reverse direction pump with straight vanes. I too am suspicious of this as a contributing factor but my limited knowledge of hydrodynamics tells me it should still pump as good as a normal pump with straight vanes. Today I will lower idle and readjust timing, carb and test again. A problem is that running 10-20 miles at 80 mph on 55 mph speed limit highways is different than running 75-80 for 2-3 hours.
> 
> An aside and unrelated question: When setting timing and carb I disconnect the vacuum advance and put vacuum gauge on full manifold vacuum and set at about 12 BTDC. When the vacuum advance is reconnected the engine speed picks up. Should I drop idle back down to curb idle speed? I'll let you know what the timing values are.


Radiator size should work for you, don't see that as an issue. *HOWEVER.........

QDuck*: I measured radiator from front of car near the top and bottom. TL (Driver side) was 141; TR 117; BL 192; BR 184. This was quite a surprise to me as previous measurements showed a large drop in temp from top to bottom.

*PJ:* Does not look right to me. BUT, maybe the reverse flow of the water pump pulls the hot water off the bottom hose/engine, sends it up through the radiator core to the top, and back out the top hose???? IF this is correct, guess what, your T-stat requires heat/hot coolant on the underside to open it. Might that be the problem? Do you have to turn your T-stat upside down facing down into the block so the hot water, going in reverse, opens the T-stat from the top hose going into the water cross-over????

_Gotta be honest, I did not consider that the reverse flow water pump might literally reverse the coolant flow and it now pulls the hot coolant out the engine from the bottom hose and pushes the coolant up through the radiator, and back into the engine through the top hose. I hope I am not sounding stupid here, but I have never run a reverse flow anything. This may be the whole problem and everything else is good??_

*QDuck:* I always thought 1000 rpm was too high anyway. However, this would have no affect on cooling at speed. 

*PJ*: Get the idle down and see what you have. At 1000 RPM's, it is possible that your mechanical advance is increasing more than you realize - this is why you need to know what you timing curve is. Cooling at high speed can be affected by your timing and namely, the vacuum advance can on the distributor.

Do you have any means to increase engine RPM speed when you use the AC? The AC on most cars will add a load on the engine and pull the engine/RPM down. Most cars will have some form of a solenoid that raises engine idle speeds up when you activate the AC. I don't know how much drag a newer system puts on the engine, which may be little. But if you set your idle at 650RPM with vacuum disconnected and AC off, and flip the AC on and the engine dies, you need the solenoid to increase engine RPM's so the engine does not quit when you need your power brakes (if you have power brakes).

*QDuck*: Started car and let idle for 15 minutes and temp came up to 180 (160 Thermostat) soon then slowly crept to 190.

*PJ:* Normal. 160, 180, 195, is the temp the T-stat fully opens. The 160 T-stat means it opens at 160. The engine will then find its own temp where it is "normal" for that engine. So if it levels/evens out at 180, that is the temp the engine want to operate at. It may creep up to 190 which is still OK just sitting still. If it were to creep to 200, then 210, then 225 just sitting still and you never moved an inch - then you have a problem. Maybe try that and not move the car for 15 minutes, then 1/2 hour. If it climbs much over 190, you have a problem. I would want both electric fans to be kicking in at 195-200 and then set to stop cooling at 180-185. The fans should be doing this automatically through temp sensors.

*QDuck*: 1/4 mile out of driveway was 198. On highway at 75-80 for about 10 miles got to 210. Then in 5th gear (~3000 rpm) at 75 mph for 7 miles went to 215.

*PJ:* Both fans should have kicked in and brought temps back down. At 3,000 RPM's you are putting a lot of heat into the engine. You must have 4.56 rear gearing because that is a lot of RPM for an OD gear. I would be happier seeing 2,300 - 2,500 RPM's in 5th 75 MPH.

*QDuck*: I measured radiator from front of car near the top and bottom. TL (Driver side) was 141; TR 117; BL 192; BR 184. This was quite a surprise to me as previous measurements showed a large drop in temp from top to bottom.

*QDuck*: When out west at 4000-6000 feet it would labor when trying to start with engine temp above 220. I did make an attempt to adjust idle mixture by ear to adjust for elevation.

*PJ:* Laboring to start is more an issue with timing than idle mixtures.

*QDuck*: I disconnect the vacuum advance and put vacuum gauge on full manifold vacuum and set at about 12 BTDC. When the vacuum advance is reconnected the engine speed picks up. Should I drop idle back down to curb idle speed? 

*PJ*: No, that is correct. Set idle speed/Initial timing on the balancer with vacuum line disconnected and plugged at the manifold source. Then when you reconnect, the timing will advance and engine will speed up. 12 BTDC may be too much. See how much your Initial timing jumps up when you reconnect the vacuum advance if you have a dial-back timing light or timing tape. If you have electronic ignition, I have read that some older dial-back timing lights do not work and will not give an accurate reading with some electronic aftermarket ignitions.


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## Baaad65 (Aug 29, 2019)

So I'm feeling dumb and need an education, what's the point of reverse flow? Does fluid get cooled better getting pumped from the bottom to the top? Never heard of such a thing, like I said maybe I'm just dumb.


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## QDuck (Sep 14, 2019)

Lots of comments and lots of responses. First, I'll address Baaad65 because that's an easy one. When you switch to serpentine belt the water pump rotates counter clockwise because that's the only way you can have one belt drive all accessories (i.e. AC, Alternator, PS, water pump.) 

Second: I don't know why I got higher temps at bottom of radiator other than I didn't use the thermometer correct. It never happened before and I measured again today more carefully and it showed 30 degrees cooler at bottom than at top.

*PJ: *You must have 4.56 rear gearing because that is a lot of RPM for an OD gear. I would be happier seeing 2,300 - 2,500 RPM's in 5th 75 MPH.* 

QDuck: *I've got 3.70 gears, tire OD is 26 in, 5th gear ratio is 0.86. Do the math and it comes out to 76 mph at 3000 RPM pretty close to what I see. 

*PJ: *Cooling at high speed can be affected by your timing

*QDuck:* Timing might be a factor. The full advance is 42 degrees i believe it should be about 36. But, it comes on at less than 2500 rpm.

*PJ:* Both fans should have kicked in and brought temps back down. 

*QDuck: *My fan controller is broken. I've been waiting 6 weeks for a replacement. In the meantime I manually switch on both fans and they run continuously. I tried running fanless on highway but it doesn't work.


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## Baaad65 (Aug 29, 2019)

QDuck said:


> Lots of comments and lots of responses. First, I'll address Baaad65 because that's an easy one. When you switch to serpentine belt the water pump rotates counter clockwise because that's the only way you can have one belt drive all accessories (i.e. AC, Alternator, PS, water pump.)
> 
> Second: I don't know why I got higher temps at bottom of radiator other than I didn't use the thermometer correct. It never happened before and I measured again today more carefully and it showed 30 degrees cooler at bottom than at top.
> 
> ...


 I have a CVF serpentine belt set up with only power steering and it rotates the same direction as the stock system did. Looking at the motor standing in front of it, it rotates clockwise so idk what kind of serpentine you have?


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## BearGFR (Aug 25, 2008)

I'm getting more and more suspicious of your serpentine belt system and turning the water pump backwards. <IF> that's reversing the direction of flow through the engine, then all bets are off. 

Double check the installation according to the vendor's instructions. 

Just for grins, have you tried running with the thermostat removed to see what happens?

Bear


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## AV68 (Aug 18, 2021)

QDuck can you post a pic of the serpentine system on your car, a pic of your engine not from the vendor web site


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## PontiacJim (Dec 29, 2012)

BearGFR said:


> I'm getting more and more suspicious of your serpentine belt system and turning the water pump backwards. <IF> that's reversing the direction of flow through the engine, then all bets are off.
> 
> Double check the installation according to the vendor's instructions.
> 
> ...



You were reading my mind. I was thinking this today myself. I might try coring the T-stat and use the outer ring like a number of race cars do. A properly set-up coolant system really does not need the T-stat - it is more for engine warm-up and winter cold so as to keep heat in the engine and the heater working.

I know they even offer blank discs that can be used in place of the T-stat and they have different size holes so you can adjust the flow as needed or dial it in.

I don't think a reverse flow, if this engine truly is, would not be a good idea on an old Pontiac engine that was not designed for such. Pontiac used reverse cooling on their early V8 engines, but changed it, so if it was really all that good, I would have thought the engineers would have kept reverse cooling.


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## Jared (Apr 19, 2013)

Another thing on a reverse flow set up. Wouldn't you need to swap the upper and lower radiator hoses for this to work properly? I can picture flow issues being caused in the radiator and in the heater core as a result of this. Just a thought.


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## AV68 (Aug 18, 2021)

Reverse flow just refers to the rotation of the water pump, the water flow through the engine would be unchanged, an older engine like Jim mentioned above would be a whole different animal
I looked at CVF and March complete systems and it looks like neither change the flow direction of the water pump
Wrong water pump on it maybe? might want to try a standard rotation high flow pump


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## QDuck (Sep 14, 2019)

Baaad65 said:


> I have a CVF serpentine belt set up with only power steering and it rotates the same direction as the stock system did. Looking at the motor standing in front of it, it rotates clockwise so idk what kind of serpentine you have?
> View attachment 155281


My system is made by Eddie Motorsports. When the compressor is added it reverses the direction of water pump. The CVF system adds three idlers so the water pump can rotate clockwise.


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## AV68 (Aug 18, 2021)

where did you get the water pump from?


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## Baaad65 (Aug 29, 2019)

QDuck said:


> My system is made by Eddie Motorsports. When the compressor is added it reverses the direction of water pump. The CVF system adds three idlers so the water pump can rotate clockwise.
> View attachment 155319


Ah ok, I only have one idler though.


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## AV68 (Aug 18, 2021)

I looked on Summit and Ruff Stuff web site and neither show reverse rotation option for Pontiac water pumps, so you might have a straight vane impeller just spinning in reverse, you might want to try and remove the serpentine system and run standard rotation just as a test for cooling


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## QDuck (Sep 14, 2019)

*Bear GFR:* I'm getting more and more suspicious of your serpentine belt system and turning the water pump backwards. 
*QDUCK: *Well, I think your suspicions are unfounded. The water pump has straight vanes and therefore will push water the same in either rotation.








I have found no tests or other evidence to support that, but looking at the picture of a reverse flow pump it seems logical. Interestingly Pontiac used reverse flow in earlier V8 engines (Pontiac Engine Cooling) and some people it seem to do it now. Has some merit in cooling heads first instead of last.

*PJ:* I am leaning more toward your remarks about timing. I've been doing more experimenting. At 85-90 F I let the car idle for 20-30 minutes with both fans running. Near the end it began to creep up to 183 F. I shut off one fan and temp quickly went to 200 but when turned back on it cooled back down to a little over 180 in just a few minutes - Sure heats up faster than it cools down! Around town it stays below 190 with normal driving. Getting aggressive may be different but I didn't do that and it still cools down satisfactorily back to normal driving. It seems that when the revs get high is when it gets hot and the higher the rev, the hotter it gets. Highway speed gets it over 2000 rpm and if I'm getting full advance already it may be they key. I had to change distributors a while ago and I never thought of checking the advance curve. I'll have to do that and see what happens. I've got a couple of trips coming up that will see extended hours at highway speed. Here at low elevation and temps usually below 90 or even 80 the system doesn't get stressed.
[
QUOTE="AV68, post: 946556, member: 94277"]
where did you get the water pump from?
[/QUOTE] 
Probably Summit Racing but I don't know the brand. I only know that I had difficulty finding one. It seems there are more out there now. e.g. FlowKooler. Removing the serpentine system and putting it back is not an option I want to consider because I never had the original belts and pulleys on the engine. It would be easier and probably cheaper to buy a different serpentine system. Tuff Stuff (If that's what you meant) does have a reverse rotation pump. That's what Eddie Motor Sports carries. (Tuff Stuff Aluminum Water Pump Pontiac 11 Bolt Reverse Rotation). Most likely these pumps are straight vane running backwards as there are none that are high flow.


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## AV68 (Aug 18, 2021)

might be worth the cost of a stock bracket, belt and good high flow water pump to find out before you invest in another serpentine set up, the link below is from the Ames catalog for a stock bracket


https://secure.amesperf.com/qilan/Image_Display?ss_max_image_width=475&ss_part_num=N142E


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## AV68 (Aug 18, 2021)

I double checked, the Tuff Stuff site doesn't show a reverse flow, but the Eddies Motorsport site does I wonder if its something made just for them?

I just clicked on the link to Ames above and it didnt work








this is what the link was part #N142E $48.00


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## AV68 (Aug 18, 2021)

forgot about the pulleys so figure another couple hundred for crank water pump and alternator pulley, that would get you enough just to test drive
I think BLK69JUDGE on this forum has a bunch of stuff like that for sale, you'll just need to be sure which timing cover you have 8 or 11 bolt water pump style, the ames link above was for an 11 bolt 

looking at you serpentine picture you could try and change the water pump for a high flow standard pump and measure for a shorter belt eliminating the AC and tension-er pulley just as a test  you would have to pry the alternator into position to get the upper bolt back in, could even try that with the pump you have

Just verify timing, vacuum and fuel mixture before you start changing anything


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## PontiacJim (Dec 29, 2012)

QDuck said:


> *Bear GFR:* I'm getting more and more suspicious of your serpentine belt system and turning the water pump backwards.
> *QDUCK: *Well, I think your suspicions are unfounded. The water pump has straight vanes and therefore will push water the same in either rotation.
> View attachment 155330
> 
> ...


Probably Summit Racing but I don't know the brand. I only know that I had difficulty finding one. It seems there are more out there now. e.g. FlowKooler. Removing the serpentine system and putting it back is not an option I want to consider because I never had the original belts and pulleys on the engine. It would be easier and probably cheaper to buy a different serpentine system. Tuff Stuff (If that's what you meant) does have a reverse rotation pump. That's what Eddie Motor Sports carries. (Tuff Stuff Aluminum Water Pump Pontiac 11 Bolt Reverse Rotation). Most likely these pumps are straight vane running backwards as there are none that are high flow.
[/QUOTE]


OK, I am still unsure if the water flow is actually reveresed, ie through the heads first via the water crossover and then down through the engine block and out the lower hose and up through the radiator?

BUT, for the sake of theory, if it is actually flowing this way, here are my next thoughts. The radiator has an expansion tank above the cooling tubes. In a normal flow system, you will have some space/air in the expansion tank.

If the coolant flow is reversed, how do you remove the air in that expansion tank? I suppose you could fill it right to the top of the tank, and hope you got all the air out of the top hose and coolant system in general. I would think if you had any air in the system, that it would find its way to the expansion tank. With this, it could be possible to have an air pocket, or even pull air into the engine at higher impellar/running speeds. Air pockets would be a bad thing.

On newer cars, there is no expansion tank. The radiator overflow tube connects to a "recovery" tank. As the engine heats up and coolant expands, it dumps into the recovery tank. When the engine cools, the reverse happens, the coolant is then pulled from the recovery tank back into the radiator. This causes the radiator to once again be topped off with coolant AND no air would enter the system.

The key here is that the radiator cap has to function in a manner to allow coolant out under pressure/expansion, and then let the radiator draw the coolant back in under vacuum caused by the cooling/contraction of the coolant fluid.

This is NOT the same as a "catch can" or "overflow tank." a recovery/reservoir tank typically features a vented cap and is not required to be above the cylinder heads. The job of the recovery/reservoir tank is to hold the coolant that is discharged from the systems pressure relief when the coolant is hot and expanding. When the system cools, the cooling affect creates a vacuum that pulls this coolant back into the system. A recovery/reservoir tank will either be plumbed at the bottom of the tank or have a hose internally that runs to the bottom so coolant can be drawn back into the system. 









Overflow Tank vs. Expansion Tank – Beyond the Checkered Flag






blog.championcooling.com


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## Baaad65 (Aug 29, 2019)

Like I said I never heard of a reverse flow system but again I haven't heard of a lot of things, but wouldn't that system make the pump work harder pushing up all that fluid? I would think gravity would be easier and the trickle down of water while the air going through the radiator just seems to make more sense. PJ seems to have a point, if it was such a good idea everyone would still be doing it that way, and another good point on the air accumulating in the top tank, these aren't sealed systems like the newer cars.


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## PontiacJim (Dec 29, 2012)

Baaad65 said:


> Like I said I never heard of a reverse flow system but again I haven't heard of a lot of things, but wouldn't that system make the pump work harder pushing up all that fluid? I would think gravity would be easier and the trickle down of water while the air going through the radiator just seems to make more sense. PJ seems to have a point, if it was such a good idea everyone would still be doing it that way, and another good point on the air accumulating in the top tank, these aren't sealed systems like the newer cars.


Believe the reverse flow system is used on the LS engines and this is where the "contemporary" thinking comes from. But, as I said, Pontiac used reverse cooling 1955-1959 ( as I recall), BUT, the water pump outlets went directly into the front of the heads - same place were the freeze plugs are on the later heads.

Note in the diagram that the water flow still uses a clockwise water pump. The "reverse" flow is reference to the water going to the heads first and then down through the block. So here is where I am confused with *QDuck*'s set-up. Does the water literally run in reverse out through the heads and back in from the block? Judging from his radiator temps, hooter at the bottom and cooler at the top, that kinda would indicate that, but who knows? In any case, I am confused because the water flow does not truly go though the heads first as seen in the earlier design where the water pump outlets do indeed connect to the front of each head to push coolant through the head first and then down through the block and back. Instead, does *QDuck*'s coolant enter the heads via the T-stat/water crossover and then through the heads/block? I don't know. Makes no sense why anyone would try this, but that's how new concepts are worked through and made better. 

Here is the whole story and pics:





__





Pontiac Engine Cooling






pontiacsafari.com


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## AV68 (Aug 18, 2021)

__





Pontiac Engine Cooling






pontiacsafari.com





This is a good explanation of the old reverse flow type cooling system

The OP has a reverse rotation water pump not reverse flow cooling system


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## Baaad65 (Aug 29, 2019)

Ok that makes more sense, I just couldn't understand how it would pump water up the radiator...learn something everyday good or bad 😉


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## PontiacJim (Dec 29, 2012)

AV68 said:


> __
> 
> 
> 
> ...


True, but this is confusing. Maybe the hot lower radiator temps and cooler upper temps were taken when the engine was heated up and T-stat not open yet? Sounded like the temps taken with the laser temp gun were when the engine was running?

In any case, does not seem to be something I can get a grasp on nor understand the reverse rotation flow water pump as applied to an older Pontiac engine having a standard flow rotation, let alone the straight vane multi-rotational flow of the impellar versus the Pontiac "curved" vane inpeller - what was Pontiac thinking when they curved the impellar vanes? 

I guess it all works out in the wash and the rotation of the water pump has no bearing on the flow of the water pump as it still pumps the coolant the same way, either as standard or reverse rotation, it is just to accomodate the type of pulley system that is used - I think that sums it up?

If so, then we are back to the "usual" items that need to be checked in order to isolate the cause of the overheating/hot running engine - which I think we have gone through and provided a thorough check list.


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## 69PonchoGoat (Jun 17, 2021)

QDuck said:


> I have a 1966 LeMans, 400 engine, T56 trans and 3.33 rear end gears. For more than two years I have been fighting cooling problems and thought it might be okay until a recent trip to southwest at high altitude and high temps (80-90 F).
> 
> The engine is a low compression, basically stock 400 with a mild cam. Factory headers. I have Griffin radiator rated for 700 HP. Dual SPAL fans at 3600 cfm full shroud with flaps to allow air flow at high speed. 16 psi cap. 160 thermostat. Unless the outside temp is in the 50s or below it will not run under 180. At 70F it's 180-190 around town with fans running full time. On highway it's about 200. When temp gets to 80+ it runs at 225 and in high 80s it will run hotter. It seems to run cooler or not heat up as quickly if the speed gets up to 80 mph but hotter at slower speeds. On my recent trip I had put heater on to keep temp below 225. That dropped the temp 10-20 degrees for some minutes but gradually crept up. Interestingly it did not matter if the heater fan was or not so I simply by-passed the heater so water ran through the hoses all the time. That way i could sill get AC. This does not make it run cooler but lengthens the time before it gets too high and helps it cool off faster if I slow down. I could not run at speed limit without it getting too hot. The engine runs 180-200F at idle in traffic and in stop and go traffic it still remains around 200 or less, significantly less than on open highway.
> 
> ...


Here are two excellent videos of cooling a 400. I think your low flow, reverse wayer pump is a likely suspect. But also good for you to know that the heater only flows from the passenger-side head, so the driver’s side is usually 10+ degrees hotter unless you do the crossover as shown in the video.


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## WillGeo (11 mo ago)

Q Duck, I recently bought a '68 GTO with original standard 400/350hp engine. I bought it in the winter and the operating temperature was OK at around 210 sitting at a light. When the warmer weather came, it was creeping up to 220-225 at a light. I did 4 things that fixed the problem, as it now runs at 195-200 degrees when it is 95 outside. First, I put an aluminum high flow radiator in it because the original 54 year old radiator was not flowing well (clogged). Then I put a high flow water pump in it, which had more blades than the stock water pump. I then ensured the clutch fan blades were within an inch of the radiator by adding the correct spacer (I have an air conditioned GTO so I needed maximum air flow to get through both the condenser and the radiator). Finally, I found that it didn't have the spring in the return radiator hose, so it could have been collapsing the hose during normal operation. After replacing/adding these items, I took it for a spin and it was fixed! BTW, I added a catch container which is not an original part on the '68 GTO, and it has been catching a small amount of overflow from the radiator and returning it as it cools.


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## flatbill (Oct 5, 2020)

If I'm reading post #10 correctly the upper radiator temp is lower than the lower radiator temp. If so there is definitely a problem with the flow direction. Or am I reading this wrong??


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## AV68 (Aug 18, 2021)

the OP addressed that in post #18, rechecked and it was 30 degrees cooler at the bottom of the radiator, maybe he just mixed up the numbers on post 10


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## flatbill (Oct 5, 2020)

AV68 said:


> the OP addressed that in post #18, rechecked and it was 30 degrees cooler at the bottom of the radiator, maybe he just mixed up the numbers on post 10


I have not seen a mention of it but do you have the 2 water tubes and rubber seals mounted behind the water pump tin baffle?


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## PontiacJim (Dec 29, 2012)

69PonchoGoat said:


> Here are two excellent videos of cooling a 400. I think your low flow, reverse wayer pump is a likely suspect. But also good for you to know that the heater only flows from the passenger-side head, so the driver’s side is usually 10+ degrees hotter unless you do the crossover as shown in the video.


Have watched that video before, Not impressed. Hmmm, was the blower motor on and drawing more heat away from the coolant coming off the back of the heads? Look at his comparison. The bottom line - outside temp 70 degrees. Aluminum heads which absorbs more heat than iron heads. Where is the real world test, iron heads, 90 degrees outside and driving the car. What speeds did he record his "other" numbers? 40 MPH, 55 MPH, 75 MPH? Stop & Go in traffic?

Not very scientific, not buying it.


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## Jared (Apr 19, 2013)

flatbill said:


> I have not seen a mention of it but do you have the 2 water tubes and rubber seals mounted behind the water pump tin baffle?


You could be onto something here. The tired 400 that came out of mine always ran hot where the high strung 461 in there now runs at 180 all day. When the engine finally blew up and I pulled it, the rubber gaskets on both of those sleeves were in extremely bad shape. I mean cracked in several places and collapsed level of bad.

I'm still leaning towards the water pump on this one but also very possible to overlook those small tubes and seals.


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## MyPopsGTO (Jul 12, 2020)

I cannot match the tech expertise of many who have commented. I am learning so much from this community. However, let me share my solution.
I have 64 GTO with a 400. Ran hot for 1.5 years. Replaced a lot of stuff. Even put in a new radiator with electric fans. Did not cool my beast. Then I ordered an ENTROPY radiator with 2 electric fans. Fans pull an amazing 5000 cfms. That did it!!! My temps stay at 180 even in 90 degree days. It is an American company and the product does exactly what they claim. I highly recommend the ENTROPY product. Good luck!! Please reach out to me with any questions.


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## larutan (Jun 27, 2018)

QDuck said:


> I have a 1966 LeMans, 400 engine, T56 trans and 3.33 rear end gears. For more than two years I have been fighting cooling problems and thought it might be okay until a recent trip to southwest at high altitude and high temps (80-90 F).
> 
> The engine is a low compression, basically stock 400 with a mild cam. Factory headers. I have Griffin radiator rated for 700 HP. Dual SPAL fans at 3600 cfm full shroud with flaps to allow air flow at high speed. 16 psi cap. 160 thermostat. Unless the outside temp is in the 50s or below it will not run under 180. At 70F it's 180-190 around town with fans running full time. On highway it's about 200. When temp gets to 80+ it runs at 225 and in high 80s it will run hotter. It seems to run cooler or not heat up as quickly if the speed gets up to 80 mph but hotter at slower speeds. On my recent trip I had put heater on to keep temp below 225. That dropped the temp 10-20 degrees for some minutes but gradually crept up. Interestingly it did not matter if the heater fan was or not so I simply by-passed the heater so water ran through the hoses all the time. That way i could sill get AC. This does not make it run cooler but lengthens the time before it gets too high and helps it cool off faster if I slow down. I could not run at speed limit without it getting too hot. The engine runs 180-200F at idle in traffic and in stop and go traffic it still remains around 200 or less, significantly less than on open highway.
> 
> ...


Get a flow cooler water pump fixed my heat issues


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## QDuck (Sep 14, 2019)

Okay, let me reiterate and expand on much of this. I do NOT have reverse flow system. The serpentine system I have makes the water pump turn counter-clockwise. When first installed I had cooling issues and replaced pump with a high flow water pump as some suggested. The high flow water pump was no better and perhaps worse. Then I installed the reverse flow pump and temperatures were 40 to 50 degrees cooler. It is not really a reverse flow pump but has straight vanes which allows the water to flow in either direction through the pump but it is less efficient than a high flow pump. The water still flows through the system as it should - not in reverse. I have all the seals and tubes that should be there and properly sealed.

A similar problem in this post (65 GTO overheating issue that has me stumped.) mentions solutions and problems like mine but nothing there has helped me either. 

I have finally decided that I am being too critical of the engine temp and settled at 230 degrees as being too hot. Nevertheless, I have since my last post tried lifting the radiator to further eliminate the possibility of air pockets. I ran the engine with cap off until it overflowed to help remove air. I also rechecked timing to see if that would help. I just completed a 2000+ mile trip during which I varied the timing to see if it would help. I also bought an auxiliary water pump (6-8 gpm) primarily to circulate water after the engine turned off but I also tried it with engine running. It was a waste money as it did neither. On my trip the situation was better. I exceeded 230 a few times climbing long hills at 70-75 mph and ambient temperatures in the 80s.I think the only thing that made any difference was the timing changes.

Some interesting sidelights. 

1. The day after my previous post, I noticed a coolant leak. It was a puddle in the valley cover edge which overflowed down to the floor. I wiped it off to try to identify the source but could not. For the next few days I watched it. It does not leak when the car is running - only when it sits still for a while. It has stopped now (I think) but I was never able to identify the source as none of the water connections on manifold were wet. 
2. This overheating problem killed my less than a year old Diehard battery because of the constant running of the fans after the engine shuts off.
3. The heat from the engine appears to wreak havoc with hydraulics. On my trip when I got stuck in long stop and goes in construction zones and rush hour city traffic the brakes would begin to seize and the hydraulic throw-out bearing would not work. Once clear of traffic, engine temp cooled down, and some air flow through compartment then both systems worked fine. I was able to solve the brake problem by decreasing the length of the push rod between booster and master cylinder.

One other comment/question. A radiator vendor at a car show told me that the radiator fan shroud could be the cause of the engine getting hotter as the speed increased. He said that if the shroud is too shallow that air gets trapped and prevents proper flow over the radiator. He said the shroud should be 4-5 inches in depth (space between radiator and shroud) to prevent this. Anyone heard of this? My shroud is about 1 1/2 inches in depth with less than 1/2 inch clearance from engine accessories. The vendor said I would probably run cooler with out a shroud because of this and suggest I try that.

Thanks everyone for all the great comments and suggestions.


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## AV68 (Aug 18, 2021)

Did you try a standard flow pump maybe something in the shape of the timing cover coolant passages doesnt work as well with a reverse flow water pump
A mechanical fan and clutch would probably be worth a try as well


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## PontiacJim (Dec 29, 2012)

QDuck said:


> Okay, let me reiterate and expand on much of this. I do NOT have reverse flow system. The serpentine system I have makes the water pump turn counter-clockwise. When first installed I had cooling issues and replaced pump with a high flow water pump as some suggested. The high flow water pump was no better and perhaps worse. Then I installed the reverse flow pump and temperatures were 40 to 50 degrees cooler. It is not really a reverse flow pump but has straight vanes which allows the water to flow in either direction through the pump but it is less efficient than a high flow pump. The water still flows through the system as it should - not in reverse. I have all the seals and tubes that should be there and properly sealed.
> 
> A similar problem in this post (65 GTO overheating issue that has me stumped.) mentions solutions and problems like mine but nothing there has helped me either.
> 
> ...


Coolant on the valley pan is typically a sign that the leak is at the rubber O-ring seal at the timing cover/manifold. You want to have the intake slightly loose and tighen down the long water pump bolt to draw that O-ring tight, then torque your intake bolts. If not, the intake is not drawn up tight against the timing cover squeezing tightly on the O-ring and it'll leak/drip and you won't see it.

Ok, so lets not go with coolant flow as you seem to have that covered. 

Temp difference, which you corrected for us, showed a 30 degree cooler temp at the bottom of the radiator, so the radiator is working.

1.) Simple test - when the fans activate can you lay a piece of common white notebook or copy paper on the front of the radiator core and let go and have the paper stick to the core due to the suction of the fans pulling air through the radiator? This should show that you have enough CFM's being drawn from the fans when in operation.

2.) You mentioned changing the timing on your trip and this seemed to help on some occasions? You have not really nailed down a timing curve for us other than Total Timing was around 42 degrees? and all in below 2,500 RPM's? This may be a clue.

What is your engine vacuum at idle? The timing and the vacuum can can be tailored to the idle vacuum. A good street cam can reduce engine vacuum and you don't want a stock vacuum can that works off of 18 inches of vacuum when your engine only has 13 inches of vacuum. The operation of the vacuum can is important in engine cooling, so it should be tailored to your engine build, not the factory one. 

What you want to know is exactly what your Total Mechanical Timing is Initial Timing at the balancer + Mechanical weights = at "X" RPM's. NO Vacuum advance connected. 9.6 compression might work with a Total of 36 degrees and bring it in around 3,000 RPM's. If you can get 36 degrees Total out of the timing, let the engine go back to idle speed and see what it says on the balancer.

Connect your vacuum advance can and watch your Idle timing at the balance and see how much it goes up, ie 10 degrees without vacuum advance, then 14 degrees with vacuum advance. It may be higher or lower based on the engine vacuum at idle. A good idle timing with the vacuum can connected seems to fall in the range of 19-22 degrees. Sometimes, ported vacuum source can work better on some engine builds, but in general, direct engine vacuum works best.

What carb are you using? I don't think you mentioned this or I am just forgetting. An Air/Fuel meter is a great tool to ensure the carb is not jetted too lean or you have a lean condition happening at speed, or simply cruising around. A lean engine will cause engine heat.

Pull a couple spark plugs since you have put some miles on the car and take a look at the nose and electrodes. Sometimes spark plugs can tell you what is going on with the carb, but not always.

Another thing I was thinking, we use "smoke bombs" to check for leaks in our big truck trailers. Some water leaks are extremely hard to find, so if there is an opening or bad sealant, the smoke will come out of it when we light it and close the trailer doors shut.

Just a wild suggestion - You might consider setting up a smoke test on your fans to see if they draw enough air. I would simply set the smoke bomb on a table of some sort about as high as the grille ( smoke bombs get hot so, put it on something steel or otherwise that won't burn something up. I would cut a large piece of cardboard (or get a large cardboard panel from Hobby Lobby in the craft area) and tape it secure to the radiator support, but over the smoke bomb - kinda like a shelf to trap the smoke. Turn on your fans, and light the smoke bomb. The cardboard should also help direct the smoke as the fans pull it through the radiator. Stand off to the side at the fender and observe the smoke flow with the fans running full blast. You may find out the smoke struggles to get through the radiator core or even see a lot of turbulence rather than good flow.

There are industrial smoke bombs or you might be able to get one we often used for July 4th. Here is what we use at our shop. We use the large ones and lay them down on a piece of aluminum and shut the doors looking for smoke coming out to find the leaks. 



http://www.metermall.com/pdfs/superior_signal/superior_signal_smoke_candles.pdf


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## lust4speed (Jul 5, 2019)

PontiacJim said:


> Have watched that video before, Not impressed. Hmmm, was the blower motor on and drawing more heat away from the coolant coming off the back of the heads? Look at his comparison. The bottom line - outside temp 70 degrees. Aluminum heads which absorbs more heat than iron heads. Where is the real world test, iron heads, 90 degrees outside and driving the car. What speeds did he record his "other" numbers? 40 MPH, 55 MPH, 75 MPH? Stop & Go in traffic?
> Not very scientific, not buying it.


Fully agree. The YouTube guy is at best a snake oil salesman and at worse an outright fraud. Coolant has to go through the length of the head to pick up heat and the more coolant sent through the radiator the more will be cooled. I'm also not that excited about electric fans, but if you do have a 30° temperature drop from top to bottom, then the radiator and fans are doing fine and your problem is elsewhere. In fact that much drop might indicate the coolant flow is too slow either from restrictions or coolant is being bypassed by the heater hose, the pump isn't flowing high enough, or the water pump bypass hole from the intake manifold to the pump has eroded and is too large. Every drop of coolant going through the heater hose or the bypass hole is coolant that is returning directly to the engine and not going through the radiator. Stock size of the bypass was a little under 3/8" max when new and I've seen them eroded out over a 1/2". Installing a pipe plug with a 5/16" drilled hole in either intake or timing cover hole solves the problem. This restricted hole still gives a good signal to the thermostat on cold starts.

I see that the OP did mention that his water pump is standard rotation. The pump turns CCW just like a stock rotation pump. I'm not a fan of the straight vane pumps, but if it works that's fine. Hard to beat a pump modeled after the original Pontiac design and most alterations are solely for selling more water pumps.

Jim is pointing you in the right direction with timing and also jetting. Too little timing or too lean really increases (retains) heat. Getting that vacuum advance working should be good for a couple miles per gallon and cooler running temps.


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## AV68 (Aug 18, 2021)

lust4speed said:


> Every drop of coolant going through the heater hose or the bypass hole is coolant that is returning directly to the engine and not going through the radiator. Stock size of the bypass was a little under 3/8" max when new and I've seen them eroded out over a 1/2". Installing a pipe plug with a 5/16" drilled hole in either intake or timing cover hole solves the problem. This restricted hole still gives a good signal to the thermostat on cold starts.


You could be on to something here if the OP doesnt have a restricted nipple coming out of the rear of the passenger side head and or if the hole at the intake manifold o ring to timing cover connection has corroded itself to big it could be allowing to much un-cooled water to mix with cooled water coming back from the radiator


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## Baaad65 (Aug 29, 2019)

In reading post #51 I'm curious about the part that was stated about the water not getting cooled that goes through the heater core, would it be beneficial to block off my heater core since I don't drive it in cool weather? I just replaced it and would like to leave the hoses in place so I would have to plug the core or hose or head nipple, would I see much of a difference in temps because I could use all the help I can when stuck in traffic on a hot day.


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## AV68 (Aug 18, 2021)

Im not sure about 65 but the 68 non air conditioning cars the coolant flows unrestricted through the heater core so even with the fan off you will get some heat dissipated through the surface area of the core itself, for that matter even the lengths of heater hose would dissipate some amount of heat


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## AV68 (Aug 18, 2021)

Baaad65 said:


> In reading post #51 I'm curious about the part that was stated about the water not getting cooled that goes through the heater core, would it be beneficial to block off my heater core since I don't drive it in cool weather? I just replaced it and would like to leave the hoses in place so I would have to plug the core or hose or head nipple, would I see much of a difference in temps because I could use all the help I can when stuck in traffic on a hot day.


If your only heating up at low speeds or in traffic you might want to look into either a smaller diameter water pump pulley or bigger diameter crank pulley, I run the same CVF set up you have and it made a big difference on my GTO but I had to have custom pulleys machined for a Bronco with the same issues

by-passing the heater core by running the hose from the rear of the passenger head directly to the timing cover inlet is a pretty common temporary fix for a bad heater core, but I think that might introduce hotter coolant back into the timing cover vs running throught the heater core first


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## Baaad65 (Aug 29, 2019)

AV68 said:


> If your only heating up at low speeds or in traffic you might want to look into either a smaller diameter water pump pulley or bigger diameter crank pulley, I run the same CVF set up you have and it made a big difference on my GTO but I had to have custom pulleys machined for a Bronco with the same issues
> 
> by-passing the heater core by running the hose from the rear of the passenger head directly to the timing cover inlet is a pretty common temporary fix for a bad heater core, but I think that might introduce hotter coolant back into the timing cover vs running throught the heater core first


The CVF wp pulley is smaller than the stock pulley, I'm pretty sure it's me not running a shroud which I'm still resisting...it's not that bad this year with three electric fans and running distilled water with two bottles of VP Racing water treatment.


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## lust4speed (Jul 5, 2019)

Baaad65 said:


> In reading post #51 I'm curious about the part that was stated about the water not getting cooled that goes through the heater core, would it be beneficial to block off my heater core since I don't drive it in cool weather? I just replaced it and would like to leave the hoses in place so I would have to plug the core or hose or head nipple, would I see much of a difference in temps because I could use all the help I can when stuck in traffic on a hot day.


The heater core itself does perform as a mini radiator but who wants to run their heater full blast on a 100° day. When the heater doors are closed off on the earlier A-bodies there is basically no heat dissipation happening with the heater core. Lets look at the process. The coolant exits the rear of the passenger head where it has passed through the block and picked up some heat off the head. The coolant exiting here goes on through the heater and finally returns to a low pressure area at the water pump pickup. Note that all the coolant that exited the head is now back at the water pump and is returned inside the engine without going through the radiator. So hot coolant goes through again and picks up more heat without being cooled Whatever flow was diverted has done nothing to cool the engine.

Same with the bypass between manifold and water pump. Flow is out the manifold crossover to a low pressure area in the water pump. Every ounce of coolant that goes through this hole is returned to flow through the engine again without being cooled. The bigger the hole and the more restriction the thermostat has the more coolant going right back into the engine.

I installed a valve in the hose between head and the heater box for use during the summertime, but its main purpose was to stop excess heat inside the car and give the AC a fighting chance of cooling off the car. Those flapper doors on the heater box were not all that great when new and are terrible now allowing a lot of heat through when we don't need it.

Another caveat is the heater cores come with the input nipple bent inward at the tip to reduce flow and therefore internal core pressure. That crimp becomes the restricted spot so that pressures in the copper core remain at a reduced level and also aid in dampening pressure waves that might eventually split the core. A stock heater nipple in the head also has a reduced internal size for the same purpose. Aftermarket aluminum heads have a fully opened brass hose fitting that doesn't have any dampening effect and the crimp in the heater core nipple becomes the only restriction to help the core live.


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## Baaad65 (Aug 29, 2019)

Ya it doesn't sound like it's worth the hassle, I'm going to leave well enough alone, thanks for the 411.


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## QDuck (Sep 14, 2019)

Mostly in reference to P. Jim's post #50 and others:

1. I traced water leak to the thermostat housing. It's not much but an irritant. Since car runs around 180-190 with no stress on I will replace before winter with 180 which should fix the leak.

2. I spoke with serpentine manufacturer and he assures me I have a high volume water pump with counter-clockwise rotation.
3. Always tinkering, I now have total timing at 39° full in around 2500 rpm. Could be better but car runs well on 93 octane so I don't want to pursue perfection at this time. Vacuum at 800 RPM is 20 in on my hand-held vacuum gauge, 18 in on my Dakota Digital dash gauge. 

Note that has nothing to do with this post but I'm so happy with tinkering results that I wanted to share it. I have been bothered since near the very beginning because I didn't think the engine ran smooth and blamed it on my mild camshaft. Also had bad vibrations I have been chasing for 2-3 years that no one could find cause of. So I found axle tubes were bent and I replaced rear end with a Ford 9 inch (I can hear the groans from here) which greatly reduced the vibrations. Then I had a new driveshaft made and it was better. Thanks to tips from Inland Empire Drive Line I found driveshaft running out about .030. I rotated and vibration still there but many people might not notice or pass it off to unbalanced tires. Car is quieter and much nicer to ride in. Then my brake pedal started squeaking then had a hissing sound and eventually brakes were self-activating. My second and 9-month old brake booster was leaking on the passenger side. Summit replaced with new booster and suddenly the car ran smooth as silk at idle - Oh happy day!

4. I tried the paper test. Fan sucks the paper in from 6 inches in front of grill. Used wood to make smoke. Not very dense but it showed the smoke sucking into radiator and coming out all around the fan opening in shroud. Also when car shut off the radiator cools from well over 200° to 90° in a very short time. The engine temp however increases at same time.

5. Timing now is 31° @ 2100 RPM and max at 32° @ 2400. Base is 11° With vacuum connected timing is at 24°. It's on a ported vacuum source as that is what is recommended for the carb. The carb is a Holley Street Avenger either 650 or 770 cfm.

6. I pulled the plugs about a month ago and they looked good clean, solid and only slightly discolored.

7. I've looked for a air/fuel meter to no avail. Just recently I saw one mentioned on this forum but can't find it now. Do you have any suggestions on a model or maker?

8. Today I got a brainstorm and wanted to ask about it but someone already answered it in this thread. That concerned the water flow through the heater core and how it goes back to the water pump. That's not doing anything to cool the water is it? I wanted to hook up an auxiliary water pump to help circulate water better, especially after shutdown. Not realizing what I was doing I put it in line with the heater. This probably just circulated the hot water if at all and did not help in getting cool water to and through the block. The directions said to place it at the outlet hose of radiator but where would you run the outlet of pump to? It seems to me such a pump should be placed either at top of radiator (e.g. inlet on heater hose and outlet into radiator or at the bottom of the radiator but where would you pump the water to? Will it help?

I'm still experimenting and trying things so keep the suggestions coming - something has to work, eh?


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## Baaad65 (Aug 29, 2019)

Nice to win some battles isn't it....my 2 cents worth is don't worry about the motor going up in temperature when shut off they all do because of no water flow getting cooled by the radiator taking the heat out of the motor. Next if it's running at 180-190° in all situations you're golden so I wouldn't worry about a secondary pump for the heater core, it's just more clutter and another place for leaks. Finally use a high flow 160° stat and drill a couple of 1/8" holes in it so it starts flowing right away and incase it sticks you'll have some water flowing through it, unless you're driving the car in the winter.















I installed a Wide Band afr meter then hid it in my glove box so I can pull it out when needed, AEM meters are good too, and are widely available on ebay. Just my amateur opinion so make sure to fact check this😉


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## QDuck (Sep 14, 2019)

Thanks, Baaa. I'll take a look at that meter.


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## QDuck (Sep 14, 2019)

SUCCESS? finally. I purchased a Davies, Craig electric water pump with fan controller.(EWP150 kit). The pump is inline with the lower radiator hose and the controller sensor is inline with the upper hose about 3 inches from the radiator inlet. For ease of installation I still have the mechanical water pump installed. I may remove impeller later and just use the pulley as an idler for belt. I left the 160 °F high flow thermostat in but drilled two 1/8" holes as recommended in this forum and by manufacturer. I also replaced the thermostat housing which was leaking with the original Pontiac one. I reinstalled the Delta PAG 16 inch fan. It doesn't flow as well as the two SPAL fans but it is much quieter and seems to work okay now. I can always switch back later if necessary.

So I ran a couple of tests. The first was at ambient air temp of 91 °F and the second was at 64 °F. The engine was at idle speed. There are three temp sensors in the system. One to the passenger side of the thermostat, one on the driver side close to the intake port of manifold and the third is in the return hose as mentioned above. Each measures different temps within 10 degrees of each other. The lowest is the one return hose. That recorded temps at idle up to almost 200 but generally the temp stabilized around 195. The EWP is factory set to run for 3 minutes after shutdown or until temp drops below the programmed value. After shutdown at 195 the temp was down to 175 and pump shut off in less than two minutes. It came back on a couple times for a few seconds and that was it.

I am really happy about that because it's been taking 20 to 30 minutes for fan to stop running in the summer weather. It was killing the battery and I would have to jump start car if i tried to start it within an hour after shutdown. Now in less than 5 minutes it cranks over albeit slightly labored but starts right up without killing battery. See the chart below.

I still have to test on the road to see if I get the same results but I am very optimistic it will be okay. I had surgery last week and have to wait at least one more week before I can drive it if doc says it's okay.

Once again I thank everyone for their comments and suggestions. I learned a lot from this thread and think others with similar problems can also get some good lessons here.


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## Baaad65 (Aug 29, 2019)

I'm not sure what the concern is if the motor temp goes up after you shut it off, it's not going to hurt anything. The biggest concern is the temp when stuck in traffic on a 90° day, that was my battle because I don't run a shroud but I've got it under control pretty much but still no parades on hot days for me.


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## Sick467 (Oct 29, 2019)

Baaad65 said:


> I'm not sure what the concern is if the motor temp goes up after you shut it off, it's not going to hurt anything. The biggest concern is the temp when stuck in traffic on a 90° day, that was my battle because I don't run a shroud but I've got it under control pretty much but still no parades on hot days for me.


 I have found that every American made V8 that I have owned has increased in temp after shutting it off. Not that I have paid that much attention to it, but I'd say 20-30 degrees, thereabouts.

The only time that it caused an issue was when the system did not have a coolant overflow tank and the radiator was filled too high. Old school coolant systems had a fill level that worked (not to the top) and anything more than that was expelled...then it pukes out what it does not want and should be fine the next go around.

All that running heat just builds up in an engine that's been shut off. I call it residual heat...it builds up after the engine is shut down, then released slowly without the help of the coolant system.


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## AV68 (Aug 18, 2021)

I guess i get a little concerned from the heat dissipating from my engine when I shut it down too but I just leave the hood open and then it gives me an excuse to stare at my engine


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## geeteeohguy (Feb 2, 2008)

Sick467 said:


> I have found that every American made V8 that I have owned has increased in temp after shutting it off. Not that I have paid that much attention to it, but I'd say 20-30 degrees, thereabouts.
> 
> The only time that it caused an issue was when the system did not have a coolant overflow tank and the radiator was filled too high. Old school coolant systems had a fill level that worked (not to the top) and anything more than that was expelled...then it pukes out what it does not want and should be fine the next go around.
> 
> All that running heat just builds up in an engine that's been shut off. I call it residual heat...it builds up after the engine is shut down, then released slowly without the help of the coolant system.


Pretty much every internal combustion engine does this as soon as it's shut down. Coolant stops circulating and heat builds. It's a total non-issue unless the radiator is over-full on a non-closed system (like our old stock GTO's). It can also cause fuel in the float bowl(s) to boil and flood the engine and dilute the engine oil. I have had this happen to me with my old '61 Corvette which runs factory dual carbs. It's a tight fit under the hood and heat has nowhere to go. Masonite spacers under each carb helped a bunch, but the new fuels we have will boil at about 140 degrees, so it's a mixed bag. It seems like the OP installed so many additional fixes to his car it makes me wonder why it's overheating in the first place. If it actually is.


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## QDuck (Sep 14, 2019)

Baaad65 said:


> I'm not sure what the concern is if the motor temp goes up after you shut it off, it's not going to hurt anything. The biggest concern is the temp when stuck in traffic on a 90° day, that was my battle because I don't run a shroud but I've got it under control pretty much but still no parades on hot days for me.


On most cars there seems to be no concern, but on mine I have two: The first is that the temp soars to over 240 at the manifold which is generally above the boiling point of water-based coolants and I think the other parts of engine are at temperatures higher than they should be. The second is that it causes my electric fan to run for 20 minutes or longer resulting in hard starting and often a dead battery. I don't know why this doesn't happen on other cars. My fan is set to shut off at 180°F.


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## Baaad65 (Aug 29, 2019)

I still don't think it's hurting anything while it's not running and that's why I put my fans on manual switches.


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