Overheating problem finally solved!

[Patrick H.]

Re: Overheating problem finally solved!

The "melt-down" of plastic items in the engine compartment is what worries me. I don't know how much of the heat can affect the nylon on timing gears but if they were week before, then they are probably shot by now.

The exhaust manifolds cracked, and the hot air blew directly at the windshield washer reservoir, thus the melting. Other underhood plastics are generally fine.

[Joe L.]

Re: Overheating problem finally solved!

The exhaust manifolds cracked, and the hot air blew directly at the windshield washer reservoir, thus the melting. Other underhood plastics are generally fine.

Patrick-----


Has a block test ever been run on the cooling system in this car? A block test is a test for exhaust gasses in the coolant. A positive test usually indicates a cracked head or block.

[Dick W.]

Re: Overheating problem finally solved!

That's true! If it jumps one tooth you can adjust the timing and get 90% of the performance back. Jump another after about 2 weeks maybe 60% jump another after another week and I barely made it home. This all occurred over a period of about 3 weeks.

Been there, done that except I was running about 85 mph on I -95 not far South of Washington DC when the nylon let go. About 3 in the morning, not a good feeling

[Kurt G.]

Re: Overheating problem finally solved!

I can't address the overheating problem, but the timing issue is interesting. I've used a local guy here in Wichita for all my engine tune/maintenance/drivability problem. We call him "carburetor Mike". He's been doing tune-up/ drivability issues on Corvettes and anything else that has a bowtie since the late 60's. he has my car set up at 15 BTDC initial advance and it runs GREAT with no knocking, dieseling or hesitation on acceleration. The only problem I have is occasional bogging down due to the quadra-jet on it. But, it's original and I'm not trying to time my hole shots. Also, my TCS works as designed, and drops the advance about 10 seconds after I shift out of 4th gear or at idle. Guess I've been lucky so far.

[Patrick H.]

Re: Overheating problem finally solved!

UPDATE -

Today I replaced the spark plug wires, and as expected that fixed the occasional, irregular miss. One of the wires was cracked and hard from heat, so at least that one was at fault. The AC Delco 508N's do fit relatively well, though I'm half tempted to trim the length on a couple so they fit better under the shielding.

I then started the car and adjusted the timing to 8 degrees BTDC at 800 rpm, which is the factory spec. I thought that if anything might stress the system this would do it. The temp seemed to remain stable while I was doing this over the course of a few minutes, and I then hooked up the full time vacuum advance and took the car for a ride. It drove well with no issues, and while driving the temp max was at the 180 degree line, just a bit above where it was when at 20 degrees BTDC. I then let it run for over 5 minutes once we arrived home, and the temp sat at the upper end of the 180 degree mark on the gauge.

We did note that the air from under the car seemed hotter at the end of the 5 min running time before the car was turned off, and I thought that items under the hood "felt" hotter than before. No IR temp gauge today, so unfortunately nothing but subjective temp data.
I'm tempted to next bump it to 12 degrees BTDC, which is the spec for LT-1s and similar motors, and see if we notice a difference. The fuel gauge suggested we were done for the day, so that will probably be later this week.

Patrick

[Timothy B.]

Re: Overheating problem finally solved!

Patrick,

IMO, until you feel the problem is corrected I would leave the timing at factory specs. Make sure the idle A/F emulsion mixture is set to allow max vacuum, lean mixtures burn slow and make the engine run hotter.

Back to the factory TCS system, could the solenoid be malfunctioning or the sender not working at the correct temperature. I would verify all the parts because I thought at high temps even at idle the system will allow full vacuum advance. If the engine runs at 180* and the only thing changed is full manifold vacuum advance you have isolated your problem.

[Jim T.]

Re: Overheating problem finally solved!

Original owner 1970 350/300 turbo 400 with 3:08 and factory air. During the first few weeks of having my new 1970 I let it idle one day with air conditioning on while out of the car. It got my attention because the idle speed increased with no one in the car. Discovered how the TCS functions. No full time vacuum 100% of the time was unsat. Bought some vacuum hose can connected full time advance and never used the TCS system, still do not use it. Never any high temps even driving in Dallas city traffic in hottest of days enjoying factory air conditioning. City gas mileage increased. Initial timing 10 degrees in use.