Event Coverage Just The Facts... Overheating SBCs

Water Wetter, stock fan or a black plastic Speedway Motors fan, remote trans cooler, radiator with 3 or 4 core rows. Yes flex fans do suck and will take your finger off. Cool off, winters on the way.

 

The only difference between ported and manifold vacuum to the vacuum advance is that with manifold you have full vacuum advance at idle. Off idle, they work exactly the same. You only get full vacuum advance when the throttle plates are open, when there is a light load on the engine. Vacuum advance is really only there for part throttle economy. Light load = high vacuum, you advance the timing. If you add load or open the throttle plates more, you lose vacuum and lose the advance. It doesn't matter if the source is below or above the throttle plates (ported).

I should note that ported vacuum isn't the same as venturi vacuum used on the old Ford Load-O-Matic distributors.

 

It sounds a lot like the problem isn't with the engine itself and more with the re-engineering of that engine into a different car without proper cooling system design. The SBC ran cool in the car it came in. Believe it or not, the engineers at GM were probably pretty bright guys that knew they had to build a car to handle idling in high temps, and the system was designed to work that way. But once someone plucked that engine and installed it into God-knows what else, all bets are off.

 

"All carbureted cars were set up with direct vacuum to the distributor before more stringent emissions requirements reared their heads.

Ported vacuum sources are a result of emissions laws and manufacturers doing whatever they could to get big V8 engines to pass smog before the incorporation of the catalytic converter."

Above quote from the superchevy article
Total BS.... Should have known that this mythology had to come from the chevy lovers
Ported vacuum was around LONG before smog controls...

jaracer has it right

 

Yes, ported vacuum was used as early as the 1940's, possibly earlier. But in the late 1960's to early 1970's when it was introduced on then modern engines, those engines were talking about and dealing with here, the purpose was specifically as part of the smog control devices to deal with newly introduced smog regulations.

 

Exactly, yes. I’m reasonably sure that the OT mid 70s muscle car idled fine without overheating. Pull the engine and drop it in a 30s car, though, and all bets are off.

Last week, I had the opposite problem. Idling downhill in 40F weather, the engine temp would drop to just over 100F from airflow alone.



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The only heat related problems I've had with my SBC was it vapor locking due to not very well placed fuel line, but since that was fixed it has ran 180-190 consistently in heat and cold. I don't think SBC's would be nearly as popular as they are if they were known to be prone to easy overheating.