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Ok so it’s been a while for me but I need you alls help. I will list everything I have done to this car since it may help with the more information you have. I am having problems with overheating while driving. If I just start it and let it idle it seems that I’m having no problem with temp regulation. But under driving whether normal or sport it will continue to run up to around 240-250 ( I have two temp gauges the original which is reading from the filler neck next to the thermostat and the aftermarket one that reads from the head. Both are reflecting the same results. I have tried everything I can think of.
I have done the following to the engine and cooling
comp cams xe 262 cam vortec heads that were redone cleared for a 600 lift Stage one dual plane intake manifold edelbrock avs 2 650 carb new cap and rotor new plugs and wires running the spark plugs as of today for the vortec now (was running for the original L48 but read on here to use the vortec. Timing is set around 8-10 btdc can’t remember off the top of my head but had it as far out as 12-14 As for the cooling I have new water pump all aluminum three row radiator 16 inch electric fan which does do better than the clutch fan I’ve noticed. New thermostat burped to cooling system multiple times now and it has a built transmission running its own cooler.
please help I’m stuck and if you need any other information please ask and I will answer to the best of my abilities
also what is the plastic piece that goes under the front of the car called I can’t think of what it would be listed under I know it is supposed to assist in airflow getting into the radiator but my car doesnt have one on it I’ll attach a picture of the area it goes in for reference
thanks in advance for all your help
The lower valance air dam is absolutely necessary for getting proper cooling airflow to a C3 radiator. It is also important that the lower radiator hose (suction side of water pump) be of non-collapsing design OR have a support spring installed inside of it (as with the factory design). A smooth-walled hose will collapse with increased pump suction when the engine is running at elevated RPM/s (over 2500 rpm; highway speeds).
A limed-up radiator and/or a malfunctioning thermostat are also common items for causing engine overheating.
Have you verified the fan clutch is working properly/right temp? (if applicable)
Where does the fan fit in relationship to the shroud (too far in/out)?
Is the shroud sealed up well on the edges with foam gaskets (like from the factory)?
Are you sure your water pump is right (spinning right direction)?
Any chance the impeller gets loose when it heats up?
Is the radiator original and clean inside (not full of minerals)?
I assume you've verified the thermostat?
Yeah, you need the lower deflector as others have said. And you'll probably need a front dam to deflect even more air up.
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1 16 inch electric fan 1150 cfm restricted and factory shroud
2. N/A I have removed the clutch fan
3. electric fan is mounted to the radiator rotation is pulling air in and blowing it towards the engine as the clutch fan did
4. it seems to be I have attached pictures for 5. I believe that it is I am attaching photos for reference as well
6. I am not sure what that is to be honest I’m sorry 😢
7. No it is aftermarket less than 3 months old and all aluminum.
8. I have tried 3 different thermostat from like 160 to 180 to the 195
presently has the 195 in it
As already stated you are missing parts under the car that force air through the radiator and also are missing seals on the top and maybe the sides between the radiator and support.
Reinstall the 180 thermostat, preferably a large mouth unit like a Stewart.
Do you have the vacuum advance on the distributor connected?
No air dam forcing air from under the chin and no seals on top of radiator will let the air go under and above the radiator NOT thru it.
I guess somebody figured that because an electric fan was installed they didn't need to direct air flow.
Leaving the shroud in place after removing the OEM clutch fan did little good.
As already stated you are missing parts under the car that force air through the radiator and also are missing seals on the top and maybe the sides between the radiator and support.
Reinstall the 180 thermostat, preferably a large mouth unit like a Stewart.
Do you have the vacuum advance on the distributor connected?
No air dam forcing air from under the chin and no seals on top of radiator will let the air go under and above the radiator NOT thru it.
I guess somebody figured that because an electric fan was installed they didn't need to direct air flow.
Leaving the shroud in place after removing the OEM clutch fan did little good.
i installed the fan and the radiator in attempt to cool things down I’m not sure what all should be there as that is everything that was there since I bought the car is still there I put the shroud back on after the electric fan because it was there before.
The fan shroud you have on there is doing you no good.
Purchase a proper shroud for an electric fan or run a search for threads here on the forum from members who have made their own,
Right now the fan is not pulling air through the radiator.
Replace all the radiator seals, because like stated earlier, you have air flowing everywhere and not being directed through the radiator.
Check the lower radiator hose to insure it can not collapse and the spring is installed.
Purchase the correct air dam and get it installed.
Double check timing.
Totally unrelated to your overheat problem, but it looks like your alternator belt is running upside down, and your power steering pump is not aligned with the crankshaft pulley. Regarding the overheating, all the above advice is right on, including replacing your fan shroud with a new one that has not been butchered up, install ALL foam strips which assure that 100% of incoming air go through the radiator and reinstalling the engine driven clutch fan. Do not depend on the electric fan to pull all necessary air through the radiator.
People love electric fans. Some people swear by them. No H.P. loss from fan belts. Much safer around fingers in the way. No slippage, etc.
But, there is more to it, of what any fan is suppose to do. Beside cooling the radiator, they also force air over / under and around the engine. External cooling is almost as important as internal cooling. An electric fan does little if anything to cool the outside of the engine.
There is a formula for calculating how many CFMs those electric fans are need compared to the square inches of the surface area of the radiator. A coverage percentage so to speak. I would guess, by your photos, you only have about 60% fan coverage. So, with that old shroud, you are only cooling about 60% capacity. The entire area around the perimeter of the fan is receiving nothing.
Just my opinion, but I think you would be better off with twin fans. A bigger ALT will be needed for their needs.
Last edited by HeadsU.P.; Mar 21, 2020 at 06:42 PM.
Totally unrelated to your overheat problem, but it looks like your alternator belt is running upside down, and your power steering pump is not aligned with the crankshaft pulley. Regarding the overheating, all the above advice is right on, including replacing your fan shroud with a new one that has not been butchered up, install ALL foam strips which assure that 100% of incoming air go through the radiator and reinstalling the engine driven clutch fan. Do not depend on the electric fan to pull all necessary air through the radiator.
Good eye on the belt. Not sure its up-side-down but its the wrong belt in relation how it rides in the pulley groove, and its SHOT! = slipping W.P.
I have a 77 as well. I've had her for over 30 years now. Back when she was bone stock. No troubles with heat. As soon as I punched it up just a little bit. The battle against overheating began. Number one thing is get all the foam back in all around that radiator. I can see gaps in your photos. The air WILL take the path of least resistance. Around your radiator! Your fan set up is s@@t!
Photo one, twin fans with shroud that covers 95 percent of the radiator. Note the foam glued to the hood, I have a high rise hood. Standard foam strip didn't fill the gap. This closes down on the strip on the support and closes gap tightly.
photo 2, I know I don't have the high buck radiator, but look into the gap between the the rad and the support, totally filled in, this must be done all the way around the radiator!
photo 3. Spoiler extension part of heavy duty cooling package from the factory. Get some bloody air in there!
Photo from 77 factory assembly manual. Showing the extension for the heavy duty cooling package and the short spoiler that you will see on most everyone's car. Plus all the brackets, etc.
This extension plus the spoiler you are missing are available from Corvette supply houses. Get them, you must get air in there.
In addition to this l also run a high flow water pump. Which is worthless without a high flow thermostat. (Ask me how I know).
Your timing will depend on a lot of things. Mostly your compression ratio and the cam your running. How much vacuum advance your running will greatly affect heat. Just having it hooked up is a lot different than actually checking just how much vacuum advance your can is truly giving you. Don't set the idle timing and call that good. Simply that won't be good enough. Base timing, total mechanical timing, when it's all in. And how much vacuum advance and when it comes in and at what vacuum level it's all in will all affect engine heat.
lots of information on this forum as per tuning.
The factory had trouble with this body style and overheating, rumours l have heard is that this body style was meant to come out in 67, but delayed for a year because they were having troubles keeping the engine cool.
Believe me, I've been there. I currently live in Australia where temps are often over 100 degrees Fahrenheit. Do ALL of these things.
Last edited by 4-vettes; Mar 21, 2020 at 06:57 AM.
Oh, and one more thing. Someone on here mentioned cooling the exterior of the engine. You'd truly be surprised by how much air those twin electrics are pushing straight at the engine. I've never measured it, but I've put my hand behind both the stock fan and the twin electrics. Night and day. Those electric fans move a lot of air. So much so I need a 50 amp relay to power them.
One other thing I noticed is the rubber fuel line running from the fuel pump to a inline filter and then rubber again to the carb.
You are tempting fate. A fire could be in your future and then you will not need to worry about cooling.
Replace all the rubber with a steel line. Easy to bend tubing line if not in stock configuration.
Need help with overheating! I am stuck
