Weird overheat problem

[mainelaker]

I am having a weird overheat problem on my 1979 L82. When driving over 45 mph or on the highway the temp gauge will raise & overheat if the speeds are not dropped down to 20-30 mph. The car is fine around town but on long drives the temp gauge will raise, I usually pull over & let her cool down so it doesn't overheat. I have pressure tested the system & it doesn't loose pressure right away but will drop down after a while. The electric fan comes on after driving so I don't think it's that, I don't remember how to test the fan clutch so I can't say how good that is. I have changed the thermoastat so I know it's not that.

 

[mainelaker]

I did some research in the forums & think I found my problem. I ordered a new front air dam & will replace the 5 blade fan with a 7 blade.

 

[Bob Chadwick]

Air dam/spoilers and tradiator seals are critical on these cars. Otherwise the air is not directed over the radiator core.

 

[jdp6000]

Do you have your front spoiler on? It purpose is to direct the air up to the rad. What thermostat did you put in...160 or 180?

Jim

 

[jdp6000]

Bob, beat me to it....

I never thought that spoiler played such a big roll until recently. I just had mine put on...big difference.

Jim

 

[Space Cowboy]

Considering the angle/pitch of a radiator in a vette, air dams are very critical to literally force and channel air through the radiator. I switched to an electric fan that Be Cool just put on the market to maximize the air flow and maintain a specific temperature.

 

[ruby76]

Here is a question that you might thnk is off topic, but is related, is your mechanical advance working properly on your HEI distributer? Mine was "stuck" in the advances position. So I set my timing (without know that) to specs. Turns out, the mech advance never advanced so at higher RPMs the timing was retarded a bit. I've read that you generate more heat when you retard timing. I just disassembled the HEI this last weekend and freed up the stuck parts and soaked in WD40. Now my mech advance is working, but I used to have same problem as you describe. I havn't interstate tested yet though. Just a thought. Does this make any sense to anyone else?

 

[mainelaker]

Yes Ruby it does make sense, the timing was off this can cause the vehicle to run hotter. I did not realize that the air dam played such a crucial role but once I started to research it, it started to make sense. I can't believe I didn't think of it before!

 

[mainelaker]

I just checked my timing & found I was at 18-20 BTDC, I adjusted it back down to spec of 12 BTDC, runs smoother & feels more responsive.

 

[bobherr46]

Gotta have the air dam!!! I just had the same problem with my 79 L-82. I replaced the missing air dam and it cools the new 406 just fine. It also seems a lot cooler in the car due to the additional air flow through the engine compartment. - Bob