Thread: new 350 rebuild running hot!!

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My guess is its the water pump. Depending on the setup, you may have installed an incorrect water pump. Try replacing the water pump with a new one. If you are running a serpentine setup use a reverse rotation. Heck it might not have even been your fault. I have gotten incorrect water pumps brand new from fairly big name stores(and catalogs). There were some years of trucks where they came with both serpentine and v belt setups. The part numbers might be close enough to make the mistake.

I put a new water pump on with the rebuild......
I am not sure exactly the chain of events here but I have found a nice solution. I changed the oil to 10w30, replaced the upper rad. hose, and drilled a pair of air bleed holes in the thermostat. Engine is running great right around 200F.