# Still to HOT



## Datold1 (Nov 27, 2018)

My 66 with 389 runs hot . I have changed water pump ,fan clutch, lower hose to one with spring. Had radiator checked and flushed. Timing is OK .and have Dakota digital gauges and sending unit.
Engine seems to gradually keep warming ,it may drop 2 or 3 degrees then climb back more. cooler air helps, hot days are a no no. I was told that the function of a fan clutch was to release at higher road speeds to let the air taken in work and not be hindered by fan. So I have 3.55 gears- is my road speed not sufficient for engine RPM. Has anyone changed from fan clutch and fan to a flex fan and spacer so that engine speed would be higher in relation to road speed?


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## AZTempest (Jun 11, 2019)

Just a thought. Have you made sure your metal guide plates behind the water pump are as close to the impeller as they can be? I adjusted both my 389 and my 326 and it gave me a few degrees difference. Defiantly helped out here in the hot Arizona heat. 

Jim


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## cij911 (Oct 25, 2017)

I went back to the clutched fan setup (better).

What type of radiator are you using? What degree thermostat are you using and have you verified it is completely opening? 

(I like to run a 180* thermostat and my car with an aluminum radiator will stay under 200* on the hottest days being raced. Driving normally, the car stays around 190*.)

What timing is the car set to base and total ?

What are is the approximate temperature coming into the radiator vs coming out (use a laser temperature gauge)?


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## Datold1 (Nov 27, 2018)

How do you adjust dividers? I put in new stainless steel ones and the back one has a notch that fits tight against the housing. 
I have tried 2 thermostats (160) and checked them in heating water both are OK. I am running original 4 core radiator made for a/c with bottom plugged because it now has 4 speed. Timing is 8 BTDC with advance
disconnected. That is the way the Mechanic set it up when he installed Pertronix Ign. I pull into driveway at 205 degrees and by the time I turn around and back it into shop it has hit as much as 230.


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## Lemans guy (Oct 14, 2014)

Do you have appropriate fan shroud? ...........That will make it run hot If not shrouded right.

Also you need a “thermostatic fan clutch”, in good shape. they have RPM activated fan clutches that look very similar, but will make it run hot.

Even the thermostatic clutches wear out gradually, do you see black oil around the fan blades? Of on the front of the water pump? May be silicone leaking from the fan clutch. If it is bad it runs up temp at idle, since that is when it works. 

When the car is cold it should barely spin by hand.....car off, goes without saying here.

8 degrees with advance disconnected,....when it is connected does it add timing? In other words is it connected to full manifold vacumn or ported vacumn? Full manifold vacumn will increase timing at idle and greatly improve idle cooling, if it is ported vacumn and 8 degrees only. It will run hotter than it should best cooling is near 20 or so, but you get the extra from vacumn advance.

Any drippage out the weep hole at the bottom of the water pump? Even new ones can leak. Some coolant leaks are hard to find. Here and you never notice them. Here is a good way to check. Get a radiator pressure tester from your auto parts or favorite vendor, or borrow one.

Start with a cold car. Put the pressure tester on the car. Start the car up and get it to normal temp, don’t drive it, right in the driveway pull in 

the garage or park it so it is clean and dry underneath. Now shut the car off and pump the pressure tester up to 16 PSI. Now go drink 4 beers , watch the game and go to bed. In the morning, go down and look under your car. If there is a leak in the coolant system, it will be evident. See if you can see where it dripped from and repair accordingly. If it gets hard to find, add some coolant dye, any auto parts store and repeat the test the next night. But this time have 5 beers, and when you get up get the black light and go check for the leak.

A temp gun will also help you diagnose it as well, I think cj said that, run the gun around the hoses and the radiator looking for hot and cold spots, may show you where there is a blockage or no flow.

If none of this works, you will have to move to Bourbon.


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## PontiacJim (Dec 29, 2012)

Datold1 said:


> How do you adjust dividers? I put in new stainless steel ones and the back one has a notch that fits tight against the housing.
> I have tried 2 thermostats (160) and checked them in heating water both are OK. I am running original 4 core radiator made for a/c with bottom plugged because it now has 4 speed. Timing is 8 BTDC with advance
> disconnected. That is the way the Mechanic set it up when he installed Pertronix Ign. I pull into driveway at 205 degrees and by the time I turn around and back it into shop it has hit as much as 230.


Get a new mechanic. The distributor advance not only can help in gas mileage, it can also help cool the engine.

I suspect you have factory high compression, 10.5:1? Pontiac engines like 10-12 Initial which may help. But, this may then change your total mechanical timing and the total timing with the vacuum advance hooked-up. So that means you will now have to address your distributor. Your total mechanical timing should be around 34 degrees, and possibly more (maybe 36) if you have the original closed chamber heads. But with high compression, you need racing gas or an octane additive or you will get engine "pinging" or detonation when you put a load on the engine.

I did not see that you listed a fan shroud? If you do not have one of these, get one.

So, you may want to refresh us on your engine build and what timing specs you do have - like total mechanical degrees @ "X" RPM.


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## AZTempest (Jun 11, 2019)

What stabilized my engine temps in the Arizona heat was to make sure the metal plates are as close to the impellers for max water flow. After I had everything else eliminated, I pulled the water pump to see how close the impellers were to the metal plates. Both my 326 and the 389 had gaps with the 389 being quit significant. I wish now I would have recorded the distance. For the 326 I was able to tap the metal plates with a mallet to reform them to narrow the gap, within approximately a 1/16 of an inch. I gained as much as 10 degrees cooler and noticed the gauge is more stable as I drive around. 

The 389 is newly rebuilt. While I was breaking in the cam, I had to shut down as the engine was trying to overheat. The gap on these plates was a good ¼ of an inch so I was unable to mallet them into position without distorting the plates. My fix was to add the shim you see in the photos and reworked the plate which took up the gap and still allows the coolant to flow. I was able to complete the break in and I’ve ran it several times with no issues although it has not been road tested yet. The shim I made from 7075-T6 aircraft aluminum .160 thick as that is what I had on had at the time. I then bonded and used aircraft rivets to secure it to the plates. 

With aftermarket water pumps, who knows how far they press the impellers on when they are manufactured. I have four pumps to compare to and all were slightly different with both cast and stamped sheet metal blade impellers. By having the larger gap in allows the coolant to cavitate, closing the gap forces the coolant though the system. It is a known issue and with a bit of searching on line you’ll find discussions about this particular problem. With everyday Arizona summer temps of 110F you do everything you can do to keep your engine in check. 

Jim


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## cij911 (Oct 25, 2017)

OK a lot of great feedback so far and I'll chime in too:

(1) Timing is incorrect and without a doubt is adding to your problem. Before connecting vacuum to the distributor , check total timing (should be ~36*). If total is not at 36*, set timing so that it is (ideally coming in by 3000 rpm. Then check base / initial timing and record. Then connect the distributor advance can to vacuum and check what your timing jumps to at idle (most likely will run much better immediately) .

(2) Get a great Aluminum radiator

(3) If you're mechanic removed timing because your compression is too high, then either run race gas or lower compression properly....(get a new mechanic)


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## Datold1 (Nov 27, 2018)

I have the correct fan shroud -according to Ames book. I haven't lost any noticeable coolant . I have not seen it boil out. I put a heat gun on it yesterday- it closely corresponded to Dakota gauge at the sending unit 
At 180degrees the head were at 375-400 the front freeze plug on rt. head was nearly 500. water flows well. I am going to hook vacuum advance back up. I put on a new fan clutch it made no noticeable difference 
The engine was fresh when I bought the and the paint was good. The heads were supposed to be done but were not so the shop drilled and installed 7/16th studs, new guides, vales, valve seats balls locks etc. they did state they took .010 off. It is bored .030 over compression is at 180. I am beginning to wonder if the shop is not looking to sell me Edelbrock hrads or some other work. Thanks Guys


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## PontiacJim (Dec 29, 2012)

Datold1 said:


> I have the correct fan shroud -according to Ames book. I haven't lost any noticeable coolant . I have not seen it boil out. I put a heat gun on it yesterday- it closely corresponded to Dakota gauge at the sending unit
> At 180degrees the head were at 375-400 the front freeze plug on rt. head was nearly 500. water flows well. I am going to hook vacuum advance back up. I put on a new fan clutch it made no noticeable difference
> The engine was fresh when I bought the and the paint was good. The heads were supposed to be done but were not so the shop drilled and installed 7/16th studs, new guides, vales, valve seats balls locks etc. they did state they took .010 off. It is bored .030 over compression is at 180. I am beginning to wonder if the shop is not looking to sell me Edelbrock hrads or some other work. Thanks Guys



Shooting the laser gun at the heads really doesn't give much info. It is the radiator you want to check. Mainly, the difference between the top and bottom to see how well the radiator is actually cooling.

How about a photo of the fan blades-to-shroud? It the fan is too far away from the shroud, it won't pull air like it should. The clutch fan used on A/C cars has a 7 blade fan that is 19 1/2" diameter. The clutch fan could be ordered on most V8 cars as an option - if this is what you have.

With 180 cranking pressure, you should have 10.5 or possibly slightly more compression. Again, assume you are running race gas/high octane or an octane booster. You probably need about 100 octane at that compression. Higher octane will not detonate like pump 91 or 93 octane and you can then adjust your timing up which may aid in cooling.


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## Lemans guy (Oct 14, 2014)

That seems awful hot for the head temperature, my exhaust manifold tuns at 375 to 400.....Heads more like 220 240....coolant 180...

Now you compression is higher than mine and that adds heat and I think your timing is too retarded and that adds heat....

Anybody running that 10.5 compression might tell us their head temp right at shutdown or even idling after a drive....

You may have to flush the hole system, could be a blockage inside, 

The coolant flows they the heater core 24/7......you could bypass the heater core, just run the hose from the water pump to the rear connector on the head and then drive it and check temps, heater core could be slowing down the flow.....


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## cij911 (Oct 25, 2017)

Lemans guy said:


> That seems awful hot for the head temperature, my exhaust manifold tuns at 375 to 400.....Heads more like 220 240....coolant 180...
> 
> Now you compression is higher than mine and that adds heat and I think your timing is too retarded and that adds heat....
> 
> ...


I only add the bypass heater core valve so as to reduce cabin heat. Technically the additional heat exchanger (heater core) should add to the cooling, not hurt.

I think your timing (too low) and crappy radiator are the problem.....


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## Lemans guy (Oct 14, 2014)

Right cj and I do that as well, bypass in the summer. However the question I am positing here is ...is the heater core blocked or restricted at all?,.....if so it can reduce the “normal flow” which goes right into the top of the head....

Since normal flow is thru heater core,.....when we bypass, we change nothing for flow, but no so if it is internally blocked. He said his heads were hot, that flow is right in the top of the head, so that is why I suggested the test for the bypass


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## Datold1 (Nov 27, 2018)

Thanks guys I think we have it figured out. If I understand it right- I had Pertronix ignition installed and it stated how to set the timing- leaving the vacuum advance disconnected. I hooked it back up and the temp has dropped about 14 degrees. so I took it back where I had some work done and they are going to used thermo whatever camera and adjust accordingly. I took it back because I was changing transmissions from a Borg-Warner to the M-21 it should have had. know anybody wanting a mid 70's B-W 4 speed 28 and 32 splined?


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## PontiacJim (Dec 29, 2012)

Datold1 said:


> Thanks guys I think we have it figured out. If I understand it right- I had Pertronix ignition installed and it stated how to set the timing- leaving the vacuum advance disconnected. I hooked it back up and the temp has dropped about 14 degrees. so I took it back where I had some work done and they are going to used thermo whatever camera and adjust accordingly. I took it back because I was changing transmissions from a Borg-Warner to the M-21 it should have had. know anybody wanting a mid 70's B-W 4 speed 28 and 32 splined?




Aha! Your mechanic must not understand directions well or spent much time under the hood of an "older" car. You do set initial timing with the vacuum advance disconnected. Once set, you reconnect the vacuum advance. :thumbsup:


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## pcguy (Jul 7, 2014)

Have you purged air from the system? Didn't see/read if the setup is more or less stock, but air in the system will definitely cause overheating.
Nick


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## mikelly2 (Nov 24, 2018)

Lot's of good info already. Just my $.02: I went round and round with heating issues. My problem was air flow. If you open your hood does it cool down? If so your problem is air flow too. One thing I didn't see asked was; is the fan about halfway into the shroud?

If it doesn't cool down with the hood up and all is right with your fan it's possible you have a head gasket leak that's letting hot exhaust gas into your cooling system. Most parts stores will have a kit to test for hydrocarbons in your coolant.


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## mikelly2 (Nov 24, 2018)

Datold1 said:


> Thanks guys I think we have it figured out. If I understand it right- I had Pertronix ignition installed and it stated how to set the timing- leaving the vacuum advance disconnected. I hooked it back up and the temp has dropped about 14 degrees. so I took it back where I had some work done and they are going to used thermo whatever camera and adjust accordingly. I took it back because I was changing transmissions from a Borg-Warner to the M-21 it should have had. know anybody wanting a mid 70's B-W 4 speed 28 and 32 splined?


Somehow didn't see this before I posted. Glad you figured it out.


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## geeteeohguy (Feb 2, 2008)

Datold1 said:


> Thanks guys I think we have it figured out. If I understand it right- I had Pertronix ignition installed and it stated how to set the timing- leaving the vacuum advance disconnected. I hooked it back up and the temp has dropped about 14 degrees. so I took it back where I had some work done and they are going to used thermo whatever camera and adjust accordingly. I took it back because I was changing transmissions from a Borg-Warner to the M-21 it should have had. know anybody wanting a mid 70's B-W 4 speed 28 and 32 splined?


No '66 GTO with a 3.55 rear gear came with an M-21. It would have come with an M-20, which has a much better first gear ratio (2.52) for getting under way with the 3.55 gears. Only 3.90-4.33 geared cars got the M-21, which had the lazy 2:20 first gear. 
I'm with the other guys.....you need a new mechanic. I would also recommend dumping the Pertronix and re-installing the factory points/condenser distributor in the interest of reliability. 
Also, these old 389's and 400's tend to run aroundd 195-215 degrees most of the time. Nothing to worry about. 230 and up? Then you can worry. Pontiacs like vacuum advance, and they like it manifold, not ported.


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## PontiacJim (Dec 29, 2012)

Just for reference, the M-20 is the wide ratio and M-21 the close ratio Muncie. The standard transmission on the GTO was a 3-speed manual with the 4-speed and automatic as an option.


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## JSK67GTO (Dec 27, 2015)

Hello, I have a 67 w/400 that would always run hot. Added fan shroud, flex fan and 160 degree t-stat and now is relatively cool (under 190) even when in town on the hot days. The shroud was the big difference for sure. Found it at Ames.


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## Datold1 (Nov 27, 2018)

Hooked the vacuum advance back up and the car seemed to run about 14 degrees cooler. the shop said it was left unhooked because of pinging- detonation; that stopped it. I am in a rural area where high octane is not 
available. So should I run 91 straight gas(no Ethanol) or 93 with and add octane boost to both? the shop is going back through it to make it right. A friend of mine has a 65 with Tri-power added and a cam and it was bored30 over and he had the ring lands blow out in 3 cylinders, so it is a worry.


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## PontiacJim (Dec 29, 2012)

*Datold1*: "A friend of mine has a 65 with Tri-power added and a cam and it was bored30 over and he had the ring lands blow out in 3 cylinders, so it is a worry."

*PJ*: Yes, it is a big worry. You can also hammer the crank bearings and destroy them in short order. You could burn a hole in a piston, or worse, have the piston bust and look through the gaping hole in the side of the block where the rod exited. *geeteeohguy* will tell you of the 428 he had that blew up because of detonation. It is one thing to hear the engine pinging, its when you don't and the damage catches you by surprise.

Again, get a new mechanic. He does not understand what a distributor is and how to adjust mechanical or vacuum advance timing or its curve. He'll blow up the engine for you doing his "thing" and you won't have to worry about gasoline choice. Sorry to be so straight forward on this.

You can add an octane booster, purchase racing gas in a drum, or even switch your fuel system over to use the higher octane alcohol in a drum. The correct thing to do is lower the compression using dished pistons IF you want to keep your heads and do not want to play "chemist" with your gasoline mixture each time. Lower the compression down to about 9.0:1 and you can most likely run the local 91 gas. Cam choice is also important. You want to have a Dynamic Compression around 7.5:1 and no more than 8.0:1 at most.

You can adjust some of your pinging out with the distributor timing and vacuum advance and tailor the advance curve to your engine. That is where I would start. Then if you don't want to pull the engine, begin adding whatever you choose in raising the octane to eliminate the last of the pinging/detonation.

You could swap out the heads with another set of 1968 and up D-port open chamber heads that have larger combustion chambers to lower the compression. This is what the factory did. Just set the heads you have off in a corner for safe keeping. And yes, the Edlebrock aluminum heads are also an option, but will be about double the cost to do iron heads.

So hard to really pin down a specific answer that will be the magic bullet to your woes. You have options and it is up to you to decide what you want to do. :thumbsup:


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## geeteeohguy (Feb 2, 2008)

And I never heard a thing when I was detonating that 428 to death. 4 or 5 broken pistons and a blue crankshaft. That engine never ran again. I've gone the detonation battle route for years. Retarding the timing to the point it won't detonate will make it sluggish and run even hotter. The answer is octane boost or lower compression. After years of fighting it with my '67, I installed bigger chamber heads (87cc instead of the 74cc) This allowed a normal timing curve and now it only detonates on 105 degree days pulling steep grades. This is on 91 octane fuel. My '65 389 GTO is at an honest 10.75 CR (milled heads, now about 63cc) and I seldom drive it due to it needing race gas. But it sure runs hard!


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## Datold1 (Nov 27, 2018)

An update on my 66 heating problem. As I previously stated- #89 would gradually but continually climb in temp. The radiator was checked for flow and I was advised it looked good. I watched the guy hold his hand over the outlet and fill through the inlet . The gushed out and drained in 2 seconds. Well I took the car back where I had been having work done: 1. to replace B-W super T-10 with M-21 and to solve heating problem.
They used an Thermal imaging heat camera and discovered that the engine would run cool as long as the water would let it then it would climb. The radiator had good flow but only across top and down to outlet.
The center portion of the radiator was clogged and water just trickled through. So now I am getting a new core put in, in order to maintain original look. The radiator never got hot enough to blow the cap and push water and watching the flow through the fill hole really looked good. I should get the car back by the ninth and that will be a good test in 90 degree and a 1 1/2 hour drive.


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## PontiacJim (Dec 29, 2012)

Datold1 said:


> An update on my 66 heating problem. As I previously stated- #89 would gradually but continually climb in temp. The radiator was checked for flow and I was advised it looked good. I watched the guy hold his hand over the outlet and fill through the inlet . The gushed out and drained in 2 seconds. Well I took the car back where I had been having work done: 1. to replace B-W super T-10 with M-21 and to solve heating problem.
> They used an Thermal imaging heat camera and discovered that the engine would run cool as long as the water would let it then it would climb. The radiator had good flow but only across top and down to outlet.
> The center portion of the radiator was clogged and water just trickled through. So now I am getting a new core put in, in order to maintain original look. The radiator never got hot enough to blow the cap and push water and watching the flow through the fill hole really looked good. I should get the car back by the ninth and that will be a good test in 90 degree and a 1 1/2 hour drive.



*PJ: "From Post #10- Shooting the laser gun at the heads really doesn't give much info. It is the radiator you want to check. Mainly, the difference between the top and bottom to see how well the radiator is actually cooling."*


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## singlesculler (Jul 7, 2019)

My '65 with Tri Power and a/c would hit 220-230 in 90 degree plus heat. I installed an aluminum radiator and a high volume water pump. Although I have yet to test it in hot weather, I have noticed on a cool day it will run 165-170 where it used to hit 195. 
Hope this helps.


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## Datold1 (Nov 27, 2018)

Final update on my 66 running hot! seems as though I bought it with an after market OEM radiator. Thermal imaging showed center half was solder blocked- the water would flow across the top an d down the passenger side to engine inlet and never have a chance to cool or circulate the inner half. Getting a new core installed.


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## John Schutt (Aug 27, 2018)

I purchased a Summit Aluminum Radiator with twin electric fans and the temp control. Never gets hot, but i don't have a lot of miles in the heat either.


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## histoy (May 22, 2019)

PontiacJim said:


> *Datold1*:
> You could swap out the heads with another set of 1968 and up D-port open chamber heads that have larger combustion chambers to lower the compression. This is what the factory did. Just set the heads you have off in a corner for safe keeping. And yes, the Edlebrock aluminum heads are also an option, but will be about double the cost to do iron heads.
> 
> If you put the '68 D-port heads on a '66 engine, do you have to change the intake manifold or exhaust manifolds as well? Any other things to consider when doing this?


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## Machinest-guy (Jul 19, 2019)

Good evening, Years ago (1970's) when I was racing my GTO and had excessive water temp in the 220+ degree F range I added an engine oil cooler and a remote oil filter. I determined my headers being close to the OEM oil filter were actually adding heat to the oil which load was transferred to the water thereby increasing it's temp. The cooler I used was from an aircraft. It is approximately 12 inches wide, 8 inches tall, and 4 inches deep. Aircraft oil coolers are built very strong and to much higher standards than automotive coolers. I mounted it in the radiator support behind the grill insert. There it gets ram air at speed. The remote filter adapter allows use of a 2 quart filter further enhancing safe engine operation. In my opinion water temps in the 220 range are not detrimental to engine life or performance if oil and inlet air temps are controlled to much lower values. I have also welded AN fittings on A/C evaporator cores to make oil coolers out of them. A/C evaporators have a very high thermal efficiency for the small size space they must fit into. Most aircraft FBO's have old oil coolers laying around their shop which were removed from service for reasons having nothing to do with their function. They are cheap or free. 

Nice clue about water pump impeller spacing from the pump baffle plate. I've moved impellers around with a press and press plate set up to get as near zero clearance as I can. Huge improvement that allows slowing the pump speed down substantially. Excessive pump speed robs H/P thrashing coolant which doesn't move out of the pump housing because the vanes have gone into cavitation. 

You should consider drilling a small 3/16th inch hole in the top of your thermostat to allow trapped air (steam) bubbles to escape before thermostat opens. The bubbles don't conduct heat very well so delay opening of the valve until surrounding metal conducts enough heat to other water sources to signal the valve to open. And when filling the system the hole allows air to escape to the radiator tanks so you actually get the system full of coolant.

May I offer a note of caution about aluminum radiators? I've used them for a long time in race and street cars. Aluminum by nature, when new and clean, transfers heat well - on par with a good copper / brass radiator. However it oxides almost instantly to form a thin insulating layer - it does so from the inside and outside. Some antifreeze products are designed to form this sort of layer to protect thin wall head castings from internal corrosion damage. Some jet wash solutions do the same thing externally. Both processes insulate heat transfer from coolant to air. The net result is aluminum radiators are consumable, and while being consumed need to be flushed often and washed externally carefully. In my opinion primary advantages for using aluminum radiators are their durability. They can take a hit and bend where a copper / brass radiator would pop a seam open. Second benefit is light weight. Third benefit is they are easy to modify and TIG weld once properly cleaned. Good cooling is the last thing on my list. 

Something not mentioned in this thread is testing for electrolysis action in the cooling system. When measuring voltage from the negative battery post to the coolant in the in the upper tank (at cap inlet) if voltage exceeds .2 volts it is time to flush and clean system to shut down the plating shop you have going on inside your engine. I believe electrolysis is the #1 cause of rotten and plugged up radiator cores as long as the engine was clean internally when assembled. 

I've found if you can get a delta of 30 degrees coolant temp between inlet and outlet hose positions on your radiator you will reject enough heat the engine can run well and live a long time. Greater delta means you have too much cooling capacity and could notch it back a bit to save weight and cut aerodynamic losses. 

Fans are a whole different subject. but I'll say now, less fan the better in my opinion.


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