Quick question:

I am running about 210- 220 w/out a/c on. I put the a/c on in TX and it immediatly shoots up to 250. I obviously have not done that again.

I had the radiator rodded? out. and they said there were no major obstructions. Should I put a new aluminun radiator in it? If so what kind?

I have heard varying opinions and don't want to put something in I don't need.

New temp sending unit and carb adjusted.

 

First check the fan clutch for tightness and then check the timing..if you don't have enough advance in it, it will run hot. The AC DEFINETLY will heat it up... On my 71 SB, it will run 170-180* all day long, idling, freeway anything.... THEN when I turn the AC on, it runs 190-215*...I never let it get past 215* if I get stuck in bad bad traffic, I turn off the ac...then I over heat....LOL

Our 69 427 car runs around 190-195* in 90-95* heat at idle....some times on the freeway running at 3000rpms, it may hit 205-210... AC not working on that one though...

Also check the seals around the radiator.

I bet its the fan clutch though...

 

The fan clutch appears to be solid. I did see about finding a heavy duty fan clutch but had no success.

I am thinking I may just be pushing it to want to run the ac but I would think it ran fine at one time. I also had the thermostat out and maybe that caused the swell in temp.

I think I will stay away from the new radiator for now. The stock one should do it.

 

Heres a checklist which will cost you nothing, or, very little expense :

1. Power wash the condensor and radiator from both sides. Be careful not to bend any fins. Get any leaves and debris out thats on the bottom.

2. Add side and top seals if there arnt any , to the radiator and condensor.

3. If you havent already...get a Prestone Cooling System Flush Kit and Prestone H.D. Cleaner. When draining, open all block drains. Flush with water for quite awhile.

4. CHeck your water pump belt ; make sure it isnt slipping.

5. With the car parked, speed up the engine to about 3,000 rpms temporarily as you see if the lower radiator hose is collapsing. If it is, bet a new reinforced one.

6. If you still overheat with A/C on, reduce coolant concentration to 75% distilled water with 25% coolant . Use a bottle of RedLine Water Wetter in the mix.

7. If you still overheat with A/C on, consider a new Stewart Stage 3 or 4 Water Pump ; i have one and it moves ALOT of water and really got my temps down. On their website, they have a Technical Forum for questions.

8. Until you are able to correct the problem, I would remove the thermostat and run without one since your going to need to use your A/C ; your engine will still come up to temperature in no time during your Texas summer, plus it will run cooler during peak daily temps outside. I did this temporarily on my 1970 BB Vette with very good results. But before you resort to this measure, do numbers 1 thru 6.

Let us know the results. Dave.

 

A number of things to check...some simple, some more involved. When you had your radiator rodded out, did you make sure all the air was bled out of the system when it was refilled? Air trapped in there takes the place of coolant and decreases efficiency.

When reinstalling the radiator, did you make sure the seals around it are properly in place? That's a major thing if they weren't reinstalled properly.

Did you have the radiator cap pressure tested? Often overlooked but it can create problems.

Is the engine actually overheating? The sending unit could be bad, though from your description it doesn't sound like this is the case.

Is the lower hose OK? If the internal spring has corroded away it will collapse at highway speeds and cause overheating.

Lots of things to check...start with the most basic and easy and go from there. When you figure it out, also add a bottle of Water Wetter or 40 Below to the system...it will help.

 

I have always found that cars run cooler when at operating temps with the thermostat in.. WIth it out, they may run cooler longer but when they do eventually heat up, the water circulates too fast through the radiator and doesn't cool off there.
Put a 160* stat back in it, drill a 1/4" hole through the side of the stat to let some water bypass to prevent air bubbles from getting choked up in there...

I would put the stat in before you go any further...They put them there more multiple reasons, not just to heat the engine up faster.

 

REPLY: You want to move more water thru the system for better cooling ; thats why going with a larger GPM Water Pump always benefits a cooling system. Its the heat transfer from the radiator to the ambient temperature that is the key factor here, and, if you move more hot water thru the radiator it will surrender more heat to the ambient air flowing across it. Ive experimented with this exhaustively on my own BB and there is no adverse affect from running without a thermostat in very hot weather. The primary purpose of the engine thermostat is to get the engine up to temp asap which makes it run smoother ,to maintain a minimum water temperature which reduces condensation in the oil , and to heat the cars interior adequately during cold weather. Thats it. For extreme outside temps, running without a thermostat doesnt pose any problems and the cooling system will operate at maximum effectiveness ; once it reaches normal operating engine temperature (with the engine thermostat out)... it will maintain it far longer and will very likely not rise to an extreme level providing you are moving . I conducted my tests in 95 f. outside temps. varying the load on the engine . The best results were when i was going 70 mph . If i lived in Texas where there is an extended season of very hot temps...I would certainly give it a try with nothing to loose. You can always reinstall the thermostat.

 

Well you could very well be right... I just know from my experience that anytime I either pulled out a stat, sped up the water pump with different pullies or ran the "hi-flow" water pumps, my cars always ran hotter... Maybe its because I live in Houston and its constant stop and start traffic... not sure. All I know is it averages 95*-98* here with 90% humidity and I have 2 big block vettes, 1 big block Grand Prix(chev 468 in it) and a SB AC car and non of them run hot here.. They all use stock cooling systems with the exception of 160* stats. Our 59 has a ZZ4 with a Griffin radiator and a GM 180* stat I believe(never looked but it runs 180* so...) it also uses a stock water pump, pullies and clutch fan.

 

I have done all of the above and more! I like the stewart pump, I would get one. Get a fan clutch as well, doc rebuild for OEM, or Hyden for better. Get a heat gun, one of those things with teh laser! I wish I would have had one. It can show you alot!!!

Check the gage! and teh sending unit! This is a big one.

I run 75/25 mix with at least two bottles of water wetter.

I have a DeWitts Rad, painted to look OEM as well. Replace the seals, another big one! Get teh carb and timing right, this made teh biggest differnece. Its all about taking small steps in the right direction. With a old BB car ... you need to get it all right or close to it. There is no one solution, its a system that lives on the edge for texas at least.

carbster

It took me alot of time and money ... and its still not 100%, maybe 80%

 

Thanks All.

 

Did I read your post correctly that you had the thermostat out when you were driving and the temp went to 250?

If so, that is the problem. You cannot run without a thermostat. The water will circulate too fast and the radiator cannot do its job of removing enought heat.

Install a 180-195 degree thermostat and see the difference.

Bob

 

I agree with the thermostat recommendation, but for other reasons.

 

I agree with the carb and timing adjustments. If you're running lean or slightly retarded timing, your thermal efficiency will be poor, and will result in higher exhaust and coolant temperatures.

 

make sure you have a good/ new rad cap with correct pressure
I think 16psi check for your car. put in a stock thermistat the one gm says for your car I think 195. then take the hose off that runs from the intake to the waterpump get a BRASS freezplug that fits tight inside that hose drill a 1/4" hole in it put it in the hose and reinstall the hose.
this hose is a bypass and sends a lot of hot water back in the motor
then use the bottle of water wetter. make sure timing is good and advances are working. they can make things overheat
jay

 

Again,..the theory that coolant can move too fast through the cooling system is an old myth. More here:

http://www.stewartcomponents.com/tec...ech_Tips_3.htm

 

This the most depated topic I've ever seen in automotive technology! .. Is there any experiment that proves or deny this myth? I know that Stewart water pumps website are trying to prove that it will help getting more heat out of the engine, but thats not credible enough to me, since its a HV water pump company anyway.

 

Coolant Too fast or Too slow??? The reason these things never die is because both arguements are right, and wrong.

The best way I can explain that is to say each radiator model has a unique "peak" cooling point. The heat rejection rate is at it's highest when a certain flow is passed through the core. More flow or less flow will reduce the heat rejection rate. GM matched the radiator with a water pump to provide the best cooling possible. The thermostat is required, providing backpressure, to maintain this flow rate.

Many people on the forum will swear by what they did for their cooling problem, and it might have actually worked, for them. It may not work for the next guy. I have the advantage of working on hundreds Corvette owners each year and they are all trying to solve of cooling problems. Occasionally weird things happen and somethings just don't make since. I am able to disregard these results as rare and go with the answers that work 90% of the time. That's one part of the problem. Someone with rare results will swear by thier solution as being the rule, not the exception, and nobody is going to convince them otherwise.

I have had people add high flow water pumps to a stock copper radiator and report higher temps. Conversely a high flow water pump would be an improvement when using one of our aluminum radiators. That's because the aluminum radiator has more cooling tubes and it's peak point (btu rating) is achived with more flow. I have had customers install high flow water pumps and then solve the cooling problem with a restrictor plate. Now they swear by restrictor plates as the answer.

Back to the BB problem....

Get an infrared gun! Shoot that stat housing when you are seeing 240 on the gauge. You might be chasing a problem that doesn't exist. The temp sending units that have been sold for the last ten years read high, misleading us to feel we have a problem.

 

Nice writeup Tom
I'll throw my .02 in on this. You must go thru the basics and eliminate them from contributing to your heat problem. Most guys have a combination of issues, hence there is no 1 Silver bullet

Coolant Flow - Radiator not stopped up, Coolant Path clear- Lower hose not collapsing

Air Flow - Radiator and condensor fins clear, Radiator seals in good shape. They deny a flow path past the radiator forcing all the air going in the front to go thru the radiator, Fan Clutch good, Fan to Shroud fit correct. (Personally, I would lose all that and go electric)

Air Dam in place and in shape

Timing and Fuel/Air mix

Gauge reading correctly, Verify with Ir Gun. They are pretty cheap now around $30. Measure at the sender and verify against the gauge. Measuring at the thermostat while interesting, will not tell you whats up with the gauge. The sender is in the drivers side head between the center cylinders and is THE hottest part of the engine.

Go thru the basics, THEN deal with mods. The BB cars were never famous for cooling, so a Dewits Rad is a good mod. A thermal clutch, fan and shroud is Not going to be the mose efficient way to move air thru it, so I highly recommend electric. Dual Spall with relays for control is one of the best recipies. The big advantage of electrics over mechanical fans is you get max flow even at idle in heavy traffic when it is most important. The advantage of aluminum rad is obviously cooling effeciency.

Good Luck

 

Who am I to argue with Tom DeWitt from whom I've purchase two radiators. But I can't go along with the theory that a system with slower moving coolant will outperform (cool the engine) a faster coolant scenario.

I agree with Stewart Components that a slow moving (low flow) system will more likely cause "hot-spots" in the engine which prevent the coolant from coming in contact with engine components which will aggravate problems such as detonation and shorten engine life. BTW, Stewart does sell stock replacement water pumps,..I believe their Stage 1 is a stock casting with a redesigned impeller.

Yes, GM engineers designed efficient cooling systems (though I'd argue BB C3's systems aren't always up to the task, especially if equipped with A/C). But their design criteria were spec'd around stock engine components.

All bets are off once you start adding HP,..heads, cam, compression, induction, etc. Again, HP = heat and HP generally means more RPM. Even the engineers at GM increased the flow as RPM's increased,..correct?