Lean condition cause high-temp?
filed in Misc Car Questions
Question: Some of you out there might know about this. My 1972 350 Chevrolet smallblock ran hot, so hot that I had to upgrade the cooling system with high-perf parts ( Milodon water pump, 4 row raditaor, high-flow thermostat) and it helped quite a lot to cool the engine at lower speeds. On the highway, though, the engine gets a bit too hot, and I was wondering, since the timing, etc. etc., have all been checked, if there could be a problem with the carburator.
Originally, this 1972 350 was in an Impala with a 2bbl carb. After a few an engine swap(s), the carburator on this engine is currently a Quadrajet from a 1979 Malibu, but this wasn’t the original carb on this Malibu as the previous owner (my cousin) was told it was from an older Corvette. This carb has more than 180000 kms on it, while the engine has something like 60000 miles on it. My main concern is that this carb could in fact be a “newer” Quadrajet that runs leaner than older ones due to emission concerns, compression ratio changes, and/or is worn out, etc. and this all, leading to a mismatched engine/carb. Engine overheating could then result with poor fuel distribution.
What would be a solution? Could there be another problem with this engine aside from the carburator? A replacement carb for the Quadrajet, like a Holley, with more adjustements capabilities? If there’s somebody out there who ever worked his way through this kind of a problem, I’d be happy to hear from him.
Answer: Don’t forget the possibility of the famous “vacuum leak”. That could cause a lean condition. Spray WD-40 or some other flamable solvent of your choice around your vacuum connections, untake manifold etc. If the idle changes, you found the spot. 1972? I think that was the first year GM used them, so it may have one, but I think that those early designs were really crappy and usually ended up being removed or disabled quite quickly cause they hurt the performance so badly.
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