# Question on cooling



## solar68 (Nov 11, 2021)

Just Installed the 461 and letting her break in for al least 300 miles.

I installed a cool fit 2 row large core radiator (1.5’ cores) and a new clutch and fan (7 blade) 

Having some odd heat issues- it has a 180 tstat, and runs 180 while driving easy. But when idling and slow driving it runs up to 210. It takes a while to get there (usually hovers around 200/205 when slow moving) the second it get going it goes right down to 180ish. This read on a mechanical gauge with the tap in the intake manifold

What do you guys think it is.

The fan sticks out a bit from the shroud (1’), and I’m using a OPGI sourced thermal clutch fan 

When driving, there is zero issue, it just seems to heat up when idling in parking lots or sitting, its drops to 180 in 30 seconds once you get going..

Thoughts?


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## armyadarkness (Dec 7, 2020)

solar68 said:


> Just Installed the 461 and letting her break in for al least 300 miles.
> 
> I installed a cool fit 2 row large core radiator (1.5’ cores) and a new clutch and fan (7 blade)
> 
> ...


A 180 thermostat will NOT keep the engine running at 180. It merely opens at 180 (I assume you knew that). So expect to see it rise into the 200 range at slow cruising and stops.

I would also expect a new motor to run on the hotter side.

FYI, personally, Id never have a Pontiac engine without running a Flowcooler water pump and a drilled thermostat... Simply because I live in a hot state with a ton of tourist traffic. Water pumps arent created equal, so if yours has a stamped impeller, they are very poor in the efficiency dept.


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## CoveKid19 (Nov 18, 2021)

What size waterpump pulley are you using? My 66 had the same temp creeping issue at idle, even with the MK-VIII fan, so I knew it wasn't an airflow problem. Once I switched to a smaller 6-1/2" AC pulley the average idle and low speed temp dropped by about 10 degrees.


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## GTO44 (Apr 11, 2016)

armyadarkness said:


> A 180 thermostat will NOT keep the engine running at 180. It merely opens at 180 (I assume you knew that). So expect to see it rise into the 200 range at slow cruising and stops.
> 
> I would also expect a new motor to run on the hotter side.
> 
> FYI, personally, Id never have a Pontiac engine without running a Flowcooler water pump and a drilled thermostat... Simply because I live in a hot state with a ton of tourist traffic. Water pumps arent created equal, so if yours has a stamped impeller, they are very poor in the efficiency dept.


^^^ X2 on the Flow Cooler water pump.

Like Army said 180degree thermostat is where it opens to BEGIN cooling. If you had a 160 thermostat it would start at 160 cooling and probably level off by 180.

If its an iron headed motor it will naturally run hotter than an aluminum headed motor.

Also, “Hot” is a subjective term. LS motors dont even turn on fan #1 until 210-215 degrees. If you get up to 200-205 and it never gets any hotter than you have no issues. Its definitely understandable to want it to run at 180. I always do. But you’re not “over heating” until you bubble fluid out of the radiator which usually happens around 245 degrees depending on your radiator cap PSI rating. Also running the motor at 200 will net more life out of a motor than running at 180. Again i love seeing my cars run at a stable 180. But if yours is a stable 200-205 in traffic and never gets any higher than the cooling system is doing its job.

For people that want to see it as low as possible in a hot climate, we will take the guts out of the thermostat and just leave the outer portion. This will allow the radiator to start cooling immediately. The cold climate guys cant do this because the motor will never heat up. Here in florida 11 months out of the year its 95-100 degrees with 100,000,000% humidity. The engine is going to heat up in a few minutes regardless of thermostat.

You also have the option of going electric fans which can move more air at idle (if you get the correct ones). But that also requires an alternator upgrade most of the time.

A small helper is Water Wetter. It can lower temps 5 to 10 degrees sometimes. For 10 bucks its worth dumping a bottle in.


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## 67ventwindow (Mar 3, 2020)

GTO44 said:


> ^^^ X2 on the Flow Cooler water pump.
> For people that want to see it as low as possible in a hot climate, we will take the guts out of the thermostat and just leave the outer portion. This will allow the radiator to start cooling immediately. The cold climate guys cant do this because the motor will never heat up. Here in florida 11 months out of the year its 95-100 degrees with 100,000,000% humidity. The engine is going to heat up in a few minutes regardless of thermostat.


 Moved to FLA in the 1970s. Both cars my family brought from up north did not make it a month before puking thier guts out in a parking lot.(no puke tank). We moved just off the main drag to the islands and would watch to see how many northern cars could not putt the 8 miles to the beach. It was a common thing even when cars were not that old.


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## armyadarkness (Dec 7, 2020)

Agreed. My VERY FIRST task on my 67 was to fix the cooling. On my recent cam swap, I blocked the intake crossover as well... that sucker is a real fun killer in the summer


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## O52 (Jan 27, 2019)

Keep in mind that the original factory installed thermostat for a 68 was 192* and the engine would normally run at 200*. If you had warning lights, the sensor was set to 230* before the overheating light would come on.
I agree with Army that the engine is still tight and will run a little warm until fully broken in and that a good water pump is essential at lower engine speeds. But there's nothing wrong with the factory pump as long as it has the cast iron impeller and the impeller is spaced correctly to the divider plate. 

Ideally the fan should be half in, half out of the shroud. If its sitting out of the shroud you're not pulling all the air through the radiator that you should be. This may be a problem at lower vehicle speeds. 
Do you have the 11 bolt water pump or the original 8? Different lengths for the 11 bolt which may be why your fan isn't where it should be. 
What brand name and part number is the OPGI clutch fan? There are different temperatures that they will engage at.


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## armyadarkness (Dec 7, 2020)

Have no idea if the OP knows the origins of his water pump, but...

For reference:


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## solar68 (Nov 11, 2021)

Wow

This is great info!

It’s a new water pump, but I don’t know the impeller type (i am inquiring) I have to assume that its the cast variety) 

I have the 8 bolt pump- and the fan blades are 1/2 way into the shroud (I didn’t know if they should be fully in the shroud) so i was thinking spacer.

I am wondering if i need a smaller pulley to turn the water pump faster, or switch it to a 160 tstat.

It sat idling yesterday for 10 mins are rose to 215/220, the second you drive off, it cools down fast, like 30 secs or so.

I’m using the stock pulleys i had off the old 400, what size is available to use to turn the pump faster?


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## armyadarkness (Dec 7, 2020)

solar68 said:


> Wow
> 
> This is great info!
> 
> ...


If you have a Pontiac 461 idling for 10 minutes at 215, in California, then your problem is slight, with room for improvement. Above all else, you need to view the cooling system as a complete system and design it accordingly. Focusing on individual parts is going to send you down the rabbit hole.

Also... dont know your engine builder, but I never saw one care about cooling... so don't assume that they built your engine to cool at maximum efficiency.


If you read our previous posts, you'll understand that dropping the thermostat "opening" temp will not help. Your car runs a 215 degrees, whether the tstat opens at 160 or 180... so again to clarify, the tstat temp is NOT what you run at, it's what you open at. Or if you prefer, your car will now start running at 215, sooner with a 160. But drilling bypass holes in the tstat WILL help.
A smaller pulley WILL help, BUT ONLY if you need it. So if you have the OEM pulley and everything else is right, then you have a problem somewhere else. A smaller pulley can be a great modification for a purpose built cooling system, but throwing a smaller pulley on to mask a crappy water pump is a waste of time. Yes, it may drop temps 20 degrees, but getting a better pump will likely drop it 20-30 degrees, too. Dont consider a pulley swap until you verify the water pump. 
If your water pump came from autozone, amazon, etc, assume that its not great. For your 8 bolt pump, the Flowcooler with the blue impeller is the best available. And... you're not just getting better flow, youre also getting better bearings.
As I said, view the system as a whole. Putting a great radiator on a system without clearanced plates and the right impeller, is like putting an 850 double pumper on a straight six with a cork in the tailpipe.


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## Lemans guy (Oct 14, 2014)

Sounds like an air flow problem at idle like the gang said, I would use a 160 testator, and make sure that you fan shouting is really well sealed around it. There was factory rubber baffles Ames sells them that seals that off. Also make sure that you wheel well flaps are in place, they actually help with the way air flows in there overall. But they effect it more at speed than idle.

agree to check the clutch fan temp, when it comes on, they do wear out and the viscous fluid inside gets old, so you may need a new fan clutch or different one. A small increase in idle RPM will help also. Itmakes the fan turn faster and water flow more.

if the cam is not stock and the engine is not stock trying to run at some factory idle setting of 500 or 600 Rpm’s can contribute to idle heating. Modified cams and engines idle higher 750 800 is ok and may run cooler.

Also retarded idle timing adds to engine heat. If you have some low idle timing like 4 or 6 BTDC that can contribute to hot idle. Best to run it at idle between 20 and 30 BTDC with 10 degrees of that coming from vac advance.

Agree with the gang, flow kooler. And 11 bolt pump is better, but yours can work.


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## Lemans guy (Oct 14, 2014)

The cooling system has to work Harder to cool something down, than it does to not let something heat up. Just like an air conditioner. Say your room is 70 degrees and you want 60 it does not have to work that hard to get there. But from 100 degrees to 60 it has to remove a lot of heat to get there.

so you would be better off to start cooling that room off with the thermostat set to 60, than leaving the AC off and letting it get to 100 and trying to cool it down.

Now army is right, as he often is that if your cooling system won’t cool good what temp the thermosat opens may not matter. However if your system is set up right, when it opens at 160 the engine starts cooling and it can more efficiently keep it cooler than when it opens at 180 and it now has that added 20 degrees to try to cool down, that is harder, and the temp climbs easier.


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## CoveKid19 (Nov 18, 2021)

solar68 said:


> I am wondering if i need a smaller pulley to turn the water pump faster, or switch it to a 160 tstat.
> 
> It sat idling yesterday for 10 mins are rose to 215/220, the second you drive off, it cools down fast, like 30 secs or so.
> 
> I’m using the stock pulleys i had off the old 400, what size is available to use to turn the pump faster?



The 6-1/2" pulleys came on AC cars and I believe the non AC pulleys were 8". AMES lists both. You can never have too much flow through the radiator so even with the best pump I'd still use the small pulley.


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## PontiacJim (Dec 29, 2012)

Option #1 -You have an air flow issue or the radiator is too small - cools down once you are moving which forces more air through the radiator.

Option #2 - You have not optimized/dialed in your timing events. Assume vacuum advance?

Option #3 - Carb running a but lean, but would not look at that until Option #2 have been verified.

Option #4 - All of the above.


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## solar68 (Nov 11, 2021)

CoveKid19 said:


> The 6-1/2" pulleys came on AC cars and I believe the non AC pulleys were 8". AMES lists both. You can never have too much flow through the radiator so even with the best pump I'd still use the small pulley.



So my car is a factory ac car, ill measure the pulley later for sure………I’m sure i have that pulley then


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## solar68 (Nov 11, 2021)

PontiacJim said:


> Option #1 -You have an air flow issue or the radiator is too small - cools down once you are moving which forces more air through the radiator.
> 
> Option #2 - You have not optimized/dialed in your timing events. Assume vacuum advance?
> 
> ...



Greta input- i actually think the carb is running really fat- i went through a tank in less than 100 miles, driving it in “break in” condition- its a bit hard starting too, takes about 10 cranks

I need to recheck timing

Radiator is a cool case they said would cool 800hp, 2 core aluminum with 1.5’ cores…

I think the fan (6 blade factory non flex) and thermal clutch is the culprit, it may not be drawing enough through.


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## solar68 (Nov 11, 2021)

It’s looks like its not far enough into the shroud


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## PontiacJim (Dec 29, 2012)

solar68 said:


> It’s looks like its not far enough into the shroud
> 
> 
> 
> View attachment 147641



A new engine can run a little hotter because it has to "loosen up" a bit, but not much hotter.

What oil weight? Oil is also a means to cool and engine. Thicker oil may not transfer heat as well as lighter oil. Just a thought.

Yes, you want 1/2 in and 1/2 out as the typical positioning.

Radiator should do the job at the specs you have.

Get a hand held laser temp gun and shoot the radiator at the top and the bottom to confirm radiator temps and there should be a noticable difference. This will also verify your gauge and can save a lot of head scratching and time if it is a gauge/sending unit issue/mismatch.

Your belts could be slipping and not know it. I have had that experience. The pulleys have a specific V angle and some of the replacement belts are close, but no cigar. They can be too skinny and not grip well, or even drop too deep and ride on the pulley center rather than the sides of the pulley. The belts that seem to be correct are the Dayco brand Top-Cogged belts.









Belt tension gauge


I have always tightened my drive / accessory belts incorrectly (no gauge). I am installing new belts on my 65 and would like to buy a belt gauge. Do any of you use a belt gauge and if so, which brand and model ? The local tool stores don't have one, so I am looking online. Thanks




www.gtoforum.com





Other things are the amount of slip from the clutch fan unit. The HD units will slip less at lower RPM's, but drag more into the upper RPM's - so pro's and con's for the real HD units. Hayden is the brand that most seem to use and I myself have used them with no issues.

The fan blades can be made at different pitches, More of a pitch/angle will cut more air at the lower RPM's.

Again, get the timing dialed in to eliminate that.

Definitely using way too much gas, in my opinion. Not good because you could be "washing down" the cylinder walls of oil and not good when breaking in a fresh engine. If you had a real healthy engine, or 3.90 gearing, I can see 10MPG's. I think you should be doing a little better.

So get that squared away as well.


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## Lemans guy (Oct 14, 2014)

Agree with solar not in the shroud at all. You could put on an 11 bolt water pump and timing cover and extend it or get another shroud and put it in. That will not cool at idle worth a dang,..you need to fix that first

you could get a different shroud from Ames and Hayden sells fan clutches with a 3 inch shaft and a low profile shaft so you could adjust. Shrouds can be cut or custom made as well.


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## O52 (Jan 27, 2019)

Pulley numbers for verification


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## solar68 (Nov 11, 2021)

PontiacJim said:


> A new engine can run a little hotter because it has to "loosen up" a bit, but not much hotter.
> 
> What oil weight? Oil is also a means to cool and engine. Thicker oil may not transfer heat as well as lighter oil. Just a thought.
> 
> ...




I’m running the recommended 20/50 ( with zinc) frost least the break in period 

Ill get that spacer- good idea, it needs to be further into the shroud i think

Ill check the belt too, that’s an easy thing to check

It’s geared at 3.55- it did a lot better before on mileage, ill check the oil for gas too

My friend recommended a straight (non clutch) flex fan, what do you think there?


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## PontiacJim (Dec 29, 2012)

solar68 said:


> I’m running the recommended 20/50 ( with zinc) frost least the break in period
> 
> Ill get that spacer- good idea, it needs to be further into the shroud i think
> 
> ...


20/50 is too heavy unless you are road racing the car. 15W-40 is better, but 10W30 might be best. The factory used 10W-30. The RA IV used 15W-40 as it had bigger clearances and was in essence a factory race engine.

I have used the non-clutch flex fan on my last 400 build. Helped with cooling. The complaint is that they do make a "whirring" sound that some feel is annoying or loud. Never bothered me. The pitch of the blades really pulled the air and then flattens out as the RPM's increase and forward motion pushes air through the radiator. They can have an RPM limit as stated by the maker, mine was rated to 6,000 RPM's - which my engine didn't see to often as power dropped off around 5,600-5,800 RPM's.

Also used the water wetter which can be bought at most auto parts stores. It did drop my temps down a few degrees, but that was my experience with it.


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## solar68 (Nov 11, 2021)

PontiacJim said:


> 20/50 is too heavy unless you are road racing the car. 15W-40 is better, but 10W30 might be best. The factory used 10W-30. The RA IV used 15W-40 as it had bigger clearances and was in essence a factory race engine.
> 
> I have used the non-clutch flex fan on my last 400 build. Helped with cooling. The complaint is that they do make a "whirring" sound that some feel is annoying or loud. Never bothered me. The pitch of the blades really pulled the air and then flattens out as the RPM's increase and forward motion pushes air through the radiator. They can have an RPM limit as stated by the maker, mine was rated to 6,000 RPM's - which my engine didn't see to often as power dropped off around 5,600-5,800 RPM's.
> 
> Also used the water wetter which can be bought at most auto parts stores. It did drop my temps down a few degrees, but that was my experience with it.



After break in, ill look at using the 15/40 for sure

I ordered a 1” and 2” spacer for the fan to put the fan closer to the radiator in the shroud 

I have a container of water wetter from another project that didn’t get used, ill throw that in too


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## O52 (Jan 27, 2019)

DO NOT USE A SPACER WITH A CLUTCH FAN! They are only intended for the flex fans.


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## solar68 (Nov 11, 2021)

O52 said:


> DO NOT USE A SPACER WITH A CLUTCH FAN! They are only intended for the flex fans.


Oh! 

Good to know, what can i do to space the fan off the pulley closer to the radiator?


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## solar68 (Nov 11, 2021)

So in doing some research, Haden has a fan clutch (2731) that’s longer than the HD pontiac one i have- ill order one and try it!


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## PontiacJim (Dec 29, 2012)

O52 said:


> DO NOT USE A SPACER WITH A CLUTCH FAN! They are only intended for the flex fans.


OK, good point and had to do some research on the fan spacer. I found some posts were the poster was going to add a spacer, but these were 3/4" to 1".

However, on the whole,_ it was recommended *NOT* to use a spacer with the clutch type fan set-up._ Several reasons came up. Many of the fan spacers do not have the pilot pin to keep the clutch fan centered and any slight off set can lead to vibrations that could take out the water pump bearing or even crack the cast iron housing of the water pump. (I also think other reasons for vibration destruction is an unbalanced/damaged fan and/or loose or sloppy bolt holes that don't center a fan)

Here is the best explanation for not using a spacer: "I would be a tad worried about the forces on the bolts, which would be extra long to deal with a spacer. On a normal fan, there are no torque differences between the fan and the pulley (through the spacers) thus no differential sheer forces on the bolts. However, a fan clutch has the fan rotating at different speeds than the fan pully, thus places sheer loads on the bolts and now those bolts are longer. The different rotational speed of the fan/clutch will try and twist the assembly in relationship to the spacer and twist the spacer in relationship to the fan pulley."

I have, and have used, *Pontiac* spacers on non-clutch fans. They had the correct pilot pin and receiving pilot pin hole on the back side which went over the water pump pin.

Since a longer drive on the clutch fan is available and would give you the extra length to move the fan deeper into the fan shroud, that would be a better way to go. However, if I only needed to move the fan forward another 1", I would use a Pontiac 1" spacer and grade 8 bolts/studs. The above mention of sheer loads would not solely be placed on the 4 5/16" fan bolts, the sheer loads would also be applied to the solid pilot pin of the spacer. If that can be sheered off, then the clutch fan would have sheered off anyway without a spacer.

This is my opinion and is what I would do if I only needed to move the fan in 1" to get it correctly positioned into the fan shroud. May not be correct, may not be recommended, might even come apart on me. I run with scissors, grind metal without safety goggles, sand without a dust mask, drive in the rain with streaking wiper blades, and listen to loud rock & roll music without ear plugs.


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## Jared (Apr 19, 2013)

I have no tech advice on this but am at similar miles and set up as you on a new engine. My old engine had the same temperature creep you described, the new one does not. Other than when I did the cam break in, mine has not gone above 185 with a 180 thermostat. I'm running the same radiator as you with the original fan clutch and shroud. The old and new engines both ran the 11 bolt water pump. I have a Flow Kooler pump on the new engine, the old one was a factory style with a cast impeller. I think the fan fits a bit closer in the shroud on the 70 than what I'm seeing in your picture. I've attached a couple pictures (please excuse the fact that I didn't paint the fan, ran out of time).


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## solar68 (Nov 11, 2021)

I do have to say, that I really appreciate the insight and support here.. if you guys were in SoCal, the beer would be on me


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## O52 (Jan 27, 2019)

OK I'm here, where's the stout? 🍺
Guinness or Murphy's please.


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## solar68 (Nov 11, 2021)

O52 said:


> OK I'm here, where's the stout? 🍺
> Guinness or Murphy's please.


I’m in Orange County, where are you located?


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## Lemans guy (Oct 14, 2014)

Murphy’s for me, since we can’t be there you are going to have to drink ours.


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## O52 (Jan 27, 2019)

San Diego South Bay 'bout a hundred miles


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## armyadarkness (Dec 7, 2020)

I know Im the oddball-out here, but I live in hot, humid, congested state and my car is a driver. I don't have radiator gaskets, a shroud, or fender flaps. Which further bolsters the proof that a well designed and maintained system works much better. 

Some day Ill add those other parts.


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## solar68 (Nov 11, 2021)

O52 said:


> San Diego South Bay 'bout a hundred miles


My parents live in Paula valley- I’m down there a few times a month, i imagine you are further southwest from there.


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## O52 (Jan 27, 2019)

South Bay, about 7 miles north of the border and 7 miles east of the ocean (I can see the Tijuana Bull Ring and the Pacific from my back yard) and 12 miles south of downtown SD.


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## Jetzster (Jan 18, 2020)

O52 said:


> (I can see the Tijuana Bull Ring and the Pacific from my back yard) and 12 miles south of downtown SD.


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## armyadarkness (Dec 7, 2020)

I can see Atlantic City, hookers, and pawn shops from my house


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## PontiacJim (Dec 29, 2012)

Here is what I see. A 530 housing development for homes $350-$450K in the making in my back yard. I now have a very valuable corner lot with street frontage and the new entrance going along the side of my property.


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## O52 (Jan 27, 2019)

so much for peace and tranquility eh Jim?


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## Jetzster (Jan 18, 2020)

armyadarkness said:


> I can see Atlantic City, hookers, and pawn shops from my house


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## PontiacJim (Dec 29, 2012)

O52 said:


> so much for peace and tranquility eh Jim?


Yep. I live on a dead end street. It winds up a hill and I am at the top as you crest over and go back down the road. I have 1 acre, my little block house sets 100 feet back from the road with trees/foliage in front to somewhat hide it and woods on the back side. Its an older neighborhood and quite, yet only 3 miles from the center of town and all its sprawl.

I just hate thinking of the cars pulling out in the morning, turning right, and just past my driveway with me trying to get out of my driveway. I may get a reputation of "that A-hole" who pulls out of that dirt driveway right in front of you and gives you the middle finger. LOL Maybe a few fights will keep this old body limbered up and in good shape? Can't wait until I get my Lemans done and I uncork the headers at 1:00 AM - I do crap like that just to annoy the snobs and their families who are no doubt going to be in my back yard. They are probably going to force me to put up a privacy fence so they don't have to look at my "old junky cars." LOL Maybe by that time I will have retired to Florida out in the boonies somewhere.

Here is the woods you see from the development side - which hides my house.


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## solar68 (Nov 11, 2021)

O52 said:


> so much for peace and tranquility eh Jim?



Next time I’m down that way, ill give you some notice, and beers will certainly be on me


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## solar68 (Nov 11, 2021)

PontiacJim said:


> Yep. I live on a dead end street. It winds up a hill and I am at the top as you crest over and go back down the road. I have 1 acre, my little block house sets 100 feet back from the road with trees/foliage in front to somewhat hide it and woods on the back side. Its an older neighborhood and quite, yet only 3 miles from the center of town and all its sprawl.
> 
> I just hate thinking of the cars pulling out in the morning, turning right, and just past my driveway with me trying to get out of my driveway. I may get a reputation of "that A-hole" who pulls out of that dirt driveway right in front of you and gives you the middle finger. LOL Maybe a few fights will keep this old body limbered up and in good shape? Can't wait until I get my Lemans done and I uncork the headers at 1:00 AM - I do crap like that just to annoy the snobs and their families who are no doubt going to be in my back yard. They are probably going to force me to put up a privacy fence so they don't have to look at my "old junky cars." LOL Maybe by that time I will have retired to Florida out in the boonies somewhere.
> 
> ...



Jim, 

I have seen your advice all over this page, i read it with interest. Someday ill be able to get you a beer..

FYI, i got the longer clutch fan and parked the fan well within the shroud. Temps have not been an issue since. Nothing over 210 when i let it idle for 25 mins.,..


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## lust4speed (Jul 5, 2019)

Thoughts to ponder.

If you approach a decent grade and the extra strain on the engine raises the coolant temperature 30° would you rather start at 160³ and end up at 190°, or start at 180° and end up at 210°?

Pontiac designed the early fan/shroud combinations to be about 2/3 in and 1/3 out, and something on the OP's engine has changed since first sold. Might have been a fan replacement, different shroud, or another half dozen possibilities. All you have to do is find what changed. The later tunnel type shrouds require the fan to be totally inside the shroud.

We tested different pulley combinations and didn't change anything else, and every time the water pump was speeded up the engine temps dropped. Best combination was the AC bottom 8" pulley and a hard to find 6" water pump pulley. Non AC cars had an under driven water pump with about a 7" on the crank and 8" on the water pump. My engine temps didn't come up until adding aftermarket AC. The combination at that point was the original 15" HO 4-core radiator and the HO 18" fan with an added SD fan clutch. First change was adding the AC pulleys and that cured the highway heat but still had some traffic increases with the air on. Gathered all the pieces over the winter and went with the deeper core 17" radiator support, 19-1/2" AC fan and matching shroud and can now sit in traffic with the AC running.

Hard to find now but we tested a 19-1/2" 7-blade Hayden flex fan against a 19-1/2" 7-blade stock AC fan and fan clutch, and performance was equal. Flex fan noise can wake the dead though.

Best return in cooling has always been clearancing the backing plate in the water pump to the impeller. Closer the better. Some tossed together pieces can have a gap of a 1/4" and that allows a massive amount of coolant to tumble past impellers and stay in the pump. Tighten up the clearance and the coolant has to be forced out of the pump.

We've tested the FlowKooler water pumps against stock units and found no measurable gain (at least they did no harm) as long as the pumps were properly clearanced. We've also not found any measurable difference between the stamped steel impeller and the cast. The cast impeller probably has a greater design efficiency, but both the Flowkooler and stamped steel impellers have more blades and that seems to equal things out.

Also haven't found any greater cooling ability with the 11-bolt pump compared to the 8-bolt, but the older pump housing and two plates takes more effort to get correct.

Last heretical thing is we have found that Pontiac run the coolest with either a properly working thermostat or no thermostat at all - and no restriction ring needed for our engines. Pontiac engines have enough internal resistance that the reduction present in the thermostat doesn't impede water flow and totally removing the thermostat doesn't do anything to speed up the coolant. There are good reasons to run a thermostat, but max cooling just doesn't happen to be one of them.


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## armyadarkness (Dec 7, 2020)

Jetzster said:


> View attachment 147902


lolololo... I can assure you that Atlantic City hookers are not nearly as well put together.


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## PontiacJim (Dec 29, 2012)

solar68 said:


> Jim,
> 
> I have seen your advice all over this page, i read it with interest. Someday ill be able to get you a beer..
> 
> FYI, i got the longer clutch fan and parked the fan well within the shroud. Temps have not been an issue since. Nothing over 210 when i let it idle for 25 mins.,..



Much better. Try some Water Wetter additive and see if that doesn't help a little more.

You want an antifreeze mixture of 50/50 in most weather, but you may want to try a 60% water (distilled water) and 40% antifreeze for summer. It is the water that takes the heat out of the engine. Read where during WWII a fighter engine (water cooled) was damaged because it over heated. The investigation revealed that the mechanic used straight antifreeze, no water added. The case was noted in one of the AAF Bulletins and stated that pure antifreeze does not dissipate heat, it was the function of the water that did this and it was recommended to use a 70/30 mix so expensive and needed engines are not ruined.

Here is what I found:

0% glycol = 217F boil point 
40% glycol = 220F boil point
50% glycol = 225F boil point 

The pressure in the system also raises the boiling point another 3 degrees per psi, so a 15 PSI cap adds another 45 degrees of boil over protection. Then 220 + 45 = 265 degrees at boil over, and my guess is that you will be pulling off the road before that number is reached.


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## lust4speed (Jul 5, 2019)

We can't use antifreeze in the drag cars so we use distilled water and Water Wetter. Over 20 years and absolutely no corrosion or rust in the coolant with that simple bottle of Water Wetter added. Made the mistake one time of picking up a bottle of green stuff from O'reilly's and within weeks there was a white residue forming inside the radiator. Drained and cleaned the cooling system and went back to Water Wetter and never saw residue again. Never bothered to test the claim that it lowers runnng temps, but just the corrosion protection makes it worthwhile.

I only use one gallon of the old fashion green antifreeze in the street cars and that's enough to protect them down to about 27° which is enough around here and that works out to about a 25% mixture. By the time you get to a 50% mix that amount of antifreeze is going to raise engine operating temps somewhat. So you have a higher boiling point adding antifreeze but the engine runs hotter so that part is pretty much a push. I don't really trust the corrosion and rust prevention of antifreeze. Long time ago I had a gallon tin of antifreeze sitting on the shelf that I forgot about. Realized I had it when the bottom of the can rusted through and drained the contents on the shelf. Since then I also add the Water Wetter to the antifreeze mix in the street cars.


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## dami98 (Jan 9, 2022)

I always like cool fashion like cool juice wrld pants and I also want best cooling environment on my vehicle.


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