Overheating When Idling

I have a '67 283 SBC in my '30-'31 Model A Roadster. It has an R4 cam, HC heads, Edelbrock carb, and a Delco HEI dist. Car runs great and stays cool when moving. Problem was it would overheat when it had to idle for more than a few minutes. The coolant temp would climb 30 deg. in that time. It has an aluminum radiator and 5-bladed belt driven 15" flex fan. I was thinking a larger fan was going to be needed to move more air when stopped and idling. This would mean installing a new water pump housing to raise the fan high enough to fit the larger fan. I was even thinking about an electric fan.

Earlier on, a couple of days ago, there was a discussion topic on electric fans. As I was reading it one poster suggested the problem may not be air movement, but ignition timing. He asked where the vacuum for the distributor advance was taken. Was it taken from a ported fitting on the carb. or from a fitting that was exposed to vacuum? Suggested vac. to the dist. should be on the vacuum fitting not the ported one. Reason he gave was if timing is not advanced enough the engine will over heat when idling. By providing vacuum all the time the timing is advanced and the engine will run cooler.

My vacuum advance tube was connected to a ported fitting on the carb. I checked the timing and it was 10 deg. BTC. I adjusted it to 6 BTC, changed the tube to the vacuum port reset the engine idle speed back to 750 RPM. The timing with vac. on the dist. moved about another 10 BTC for about 26 BTC at idle. I let it idle away for 10 minutes and the temp only moved 5 deg. Much improved and it did not cost me a cent.

I forget who you are but a big thank you for this suggestion.

(o{}o)

 

EDIT: Just read the rest. That's a big improvement!

 

My Chevy had the same problem, but once it got hot, no amount of air would help. My distributors advance was frozen so it was running retarded all the time. Switched to another distributor and now she runs cool all the time.

 

........and a shroud goes a long way.

 

I remember that post

Glad you got headed in the right direction

 

Had the same exact problem on my deuce roadster, Last year I installed a fan shroud and my problem went away.

 

I had the same problem, only moving, i'd boil off going uphill so i ran up and down the same hill moving the timing by 2 or so degrees untill it stopped overheating.

 

Shaggy, did you advance the timing or retard?
I'm having that problem on my SBC too.

 

I have to ask. Since I have never seen a car over heat because of time ing, Cant you hear the engine detonate? It would have to be past the point of any performance gain, and be doin some serious detonating to even ad the slightest of temp....

I am not discounting it as untrue, but man, I would think a lean fuel mixture would create a bigger heat issue then timing.

I have had 35 degrees afvanced (all in) at 2500 rpms, no heat. I time based on performance. The take a reading after I am done.

http://www.aa1car.com/library/overheat.htm

 

Interesting. I have had the opposite experience. I had hooked the advance to the manifold vacuum because it made the engine feel more responsive. But I couldn't keep it cool. Moving back to the ported vacuum solved the issue.

I think in your case the logic is: more timing advance > faster idle & more vacuum > lower idle setting > richer idle. I think the idle jets give more fuel with more vacuum. The less air you let in, the richer the mixture


Sent from my Verizon 4G LTE smartphone

 

Flat heads are very sensitive to timing/overheating.

 

OK.... He has a 283 SBC ?

 

Thanks to all for your read and comments. We all learn from others experiences and knowledge. I know I sure did. Pretty well know fact, now that I think of it, that retarded timing will cause over heating and loss of performance, and timing that is too advanced will cause pinging. Since the initial timing is at 6 deg. BTC with the vacuum line disconnected there should be no problem with pinging or detonation. The engine seems to idle smoother too.

(o{}o)

 

Also important to have a thermostat or at least some type of restriction to slow down the flow so it stays in the radiator long enough to cool.

 

You may want to reconsider the flex fan - here's my "$500 flex fan" - they are notorious for this....

 

Had the "only got hot while idling" problem. Mine was that I had installed a new waterpump pulley that was larger than the old one, when I would rev it up the temp would go down, and I run an electric fan so it moved the same amount of air at all rpms. Switched back to my old/smaller pulley idles at 195° no prob.

 

Well actually most any motor is affected, but you said " I have never seen a car over heat because of time ing" ? I was stating that flatheads are especially prone to overheating from improper timing.