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Hi there! I got a 81’ with a 383 in it. The only problem is it’s running a bit hotter than I believe it should be. It runs smooth and then as I’m driving it starts to rise around 230°. I’ve changed my thermostat so know I’m running a 160° instead of a 180°. And I also have a dual fan and a 4 row radiator. Could anyone recommend or help with what I can do to keep it running at a lower temp? Thank you!
Others may have more, but here are the standard questions:
What is your timing set to?
Is there a spring in your lower radiator hose to keep it from collapsing?
How are you measuring your temperature, and have you confirmed the readings with an IR temp gun?
Pictures help, too! Please post some photos of your engine compartment from various angles with the air cleaner assembly removed. Someone might spot something obvious.
Go to harbor freight and get a cheap temp gun (especially if you don't have a routine use for it). Check your temp and compare it to your gauge. I would suspect your indication is reading high.
What temp sender do you have in it?
Originally Posted by Marco Romero
Hi there! I got a 81’ with a 383 in it. The only problem is it’s running a bit hotter than I believe it should be. It runs smooth and then as I’m driving it starts to rise around 230°. I’ve changed my thermostat so know I’m running a 160° instead of a 180°. And I also have a dual fan and a 4 row radiator. Could anyone recommend or help with what I can do to keep it running at a lower temp? Thank you!
As stated, verify actual heat with a gun. Check timing...you should be at about 34-36 degrees total depending on your setup. Total timing is at or around 3000 rpm. Retarded timing is #1 cause of overheating for engines in tight places like under the hood of a C3. If you do get a cheap infrared gun....shoot it at the header tubes and check those temps.....timing that is way off can cause EGT's to rise from 600 to 900 degrees at idle......plus the engine will make more power and run better over all.
Being an 81, do you have all the factory air dam components and radiator seals installed? The 81 has a lower air valance and lower rubber extensions that is required to keep it cool.
Yep, those foam seals around the fan shroud need to be in place. Otherwise the fan will be pulling air from *around* the shield and a lot less air through the radiator itself. That's the simple, cheap fix for a lot of C3 cooling problems (assuming the engine is otherwise running properly)
Others may have more, but here are the standard questions:
What is your timing set to?
Is there a spring in your lower radiator hose to keep it from collapsing?
How are you measuring your temperature, and have you confirmed the readings with an IR temp gun?
Pictures help, too! Please post some photos of your engine compartment from various angles with the air cleaner assembly removed. Someone might spot something obvious.
What should my RPM’s be at when I check my idle timing? I had them at around 800 and it showed that the idle was at 12 w/o vacuum. With vac it went up to 18. Only problem was at 3,000 RPM my total was all the way up at 42.
The hose was a flexible with steel inside so I don’t believe it is collapsing.
I will look at the temp with a IR gun. I’ve been currently going off my temp gauge in car.
Being an 81, do you have all the factory air dam components and radiator seals installed? The 81 has a lower air valance and lower rubber extensions that is required to keep it cool.
I don’t believe I have one, when I bought the car I never saw anything like that and this is the bumper that it has from when I bought it.
Go to harbor freight and get a cheap temp gun (especially if you don't have a routine use for it). Check your temp and compare it to your gauge. I would suspect your indication is reading high.
What temp sender do you have in it?
I ordered just a OEM sender so I could use the one wire from the stock harness.
From: Arizona - If you don’t know CFI, STOP proliferating the myths around it...
I do not believe you have any issue with your bottom hose at all. The reason being, if the hose is indeed collapsing at WOT, you will know it right away. The pressure will build up rapidly in the block and usually the weakest point will be the water pump gaskets. They will blow out for sure. Ask me how I know this. If you are not drawing air directly through the radiator you have an issue and sealing things up around the edges is a MUST. GL
Nice looking engine! Thanks for posting photos. It looks like you are missing the stock light/louver combo for the front, and the lower valance as @MattoonVette pointed out.
Originally Posted by Marco Romero
What should my RPM’s be at when I check my idle timing? I had them at around 800 and it showed that the idle was at 12 w/o vacuum. With vac it went up to 18. Only problem was at 3,000 RPM my total was all the way up at 42.
The hose was a flexible with steel inside so I don’t believe it is collapsing.
I will look at the temp with a IR gun. I’ve been currently going off my temp gauge in car.
What @Jebbysan posted was the most important part. You may be dead-on, if the vac advance is consistent (perhaps it is limited to 6 degrees?) You want 36 degrees of mechanical advance at the "all in" RPM. That means vac advance disconnected and plugged. You change the springs in the dist to dial in the "all in" point, such that mechanical advance stops advancing at higher RPM. The vac advance should be 10-12 additional degrees. The Look for posts by @lars and email him for his timing and HEI papers. He may have a Holley carb paper, too.
Good news on the lower radiator hose. Sounds like the stock spring is intact, so unlikely to be the issue.
Please take some measurements with the IR gun (Lots of choices in the $20-30 range at Amazon). Between a possibly hot-reading sender, and fixing the lower valance, you should be all set!
Bonus photos of my 80 with an intact (but replaced) lower valance (in the first photo, the block drain is open)
The lack of the valance and the two lower air dams can most definitely cause your overheating issues when you are at speed. Get those parts I showed you in the picture earlier. It will never stay cool when you are running it down the road without those parts installed.
Originally Posted by Marco Romero
I don’t believe I have one, when I bought the car I never saw anything like that and this is the bumper that it has from when I bought it.
As stated, verify actual heat with a gun. Check timing...you should be at about 34-36 degrees total depending on your setup. Total timing is at or around 3000 rpm. Retarded timing is #1 cause of overheating for engines in tight places like under the hood of a C3. If you do get a cheap infrared gun....shoot it at the header tubes and check those temps.....timing that is way off can cause EGT's to rise from 600 to 900 degrees at idle......plus the engine will make more power and run better over all.
Jebby
So I used a IR gun and pointed at the intake manifold as well as the front of the block and I was getting a reading of 165. Which doesn’t seem right at all. When I pointed at the headers I got about 775°.
Nice looking engine! Thanks for posting photos. It looks like you are missing the stock light/louver combo for the front, and the lower valance as @MattoonVette pointed out.
What @Jebbysan posted was the most important part. You may be dead-on, if the vac advance is consistent (perhaps it is limited to 6 degrees?) You want 36 degrees of mechanical advance at the "all in" RPM. That means vac advance disconnected and plugged. You change the springs in the dist to dial in the "all in" point, such that mechanical advance stops advancing at higher RPM. The vac advance should be 10-12 additional degrees. The Look for posts by @lars and email him for his timing and HEI papers. He may have a Holley carb paper, too.
Good news on the lower radiator hose. Sounds like the stock spring is intact, so unlikely to be the issue.
Please take some measurements with the IR gun (Lots of choices in the $20-30 range at Amazon). Between a possibly hot-reading sender, and fixing the lower valance, you should be all set!
Bonus photos of my 80 with an intact (but replaced) lower valance (in the first photo, the block drain is open)
So I was able to get my “all in” timing at 36. Except when I checked the idle with vacuum advance, I was getting 6-8. Idle without the vacuum was at 12. Any opinions on this?
So I used a IR gun and pointed at the intake manifold as well as the front of the block and I was getting a reading of 165. Which doesn’t seem right at all. When I pointed at the headers I got about 775°.
165 could be correct. Try shooting at the upper (and lower) radiator hose. The black rubber material may give a more accurate reading. Either way, I'd trust the IR gun before I trust the gauge in the car.
Originally Posted by Marco Romero
So I was able to get my “all in” timing at 36. Except when I checked the idle with vacuum advance, I was getting 6-8. Idle without the vacuum was at 12. Any opinions on this?
So you have 30 degrees mechanical advance in your dist? And with the vac can connected, you were at 12 BTDC, or the can gave an extra 12 for 18 BTDC? Be sure the vacuum can is connected (directly) to the manifold vacuum port on the carb. Check with your finger if you don't have a vacuum gauge. And get a vacuum gauge.
Last edited by Bikespace; Aug 4, 2023 at 11:22 PM.
165 could be correct. Try shooting at the upper (and lower) radiator hose. The black rubber material may give a more accurate reading. Either way, I'd trust the IR gun before I trust the gauge in the car.
So you have 30 degrees mechanical advance in your dist? And with the vac can connected, you were at 12 BTDC, or the can gave an extra 12 for 18 BTDC? Be sure the vacuum can is connected (directly) to the manifold vacuum port on the carb. Check with your finger if you don't have a vacuum gauge. And get a vacuum gauge.
So before I changed the timing the engine was dynoed.. the idle timings were good, except the total at 3,000 was 42-44. (BTDC) The car still ran good but I thought it was weird being so high. So I changed it so the total is 36, the idle without vac was around 12. When I checked isle with vac it sat around 8. (All BTDC). Should I leave the timing how it was dynoed or do I try and change it to the 32-36 total?
383 Running Hot!
