Help ! I just fired up my newly rebuilt 348 and it's overheating...maybe. From the start the block and heads were all checked for cracks and hot tanked, bored 30 over, triple cut valves, hardened seats, 325 hp cam w/ hydraulic lifters. The engine is on a running engine stand, radiator w/ electric fan, that should cover all the background info I think. It acts like it has a major air pocket, I would start it and let it run for 5 min or so with the radiator half full and it just pushed almost all the water out the radiator, i checked the thermo before installing it, could it be a bad water pump? It's the original, I never worked with one of these classics before and most certainly don't want to crack a head...or worse. There is no water in the oil so everything looks ok, i'm fairly confused and thinking that I'm missing something special with these engines. I have built many engines in the past so no stranger to a fresh start, any suggestions would help, thanks
new 348 build
- Thread starter Paulss
- Start date
Have you tried the same with the radiator full, from cold until the thermostat opens. This way you can check for bubbles etc. the head of the radiator should be above the thermostat housing to assist in clearing an air lock.
Make sure your timing is right or very close. There was a thread in the last 12 months about possible overheating on a new build.
Good luck with the fault finding.
Make sure your timing is right or very close. There was a thread in the last 12 months about possible overheating on a new build.
Good luck with the fault finding.
Remove the thermostat,fill the engine with water,re-install the thermostat,and fill the radiator to about 1/2 inch below the filler neck in the radiator.as Mike suggested,drilling the thermostat is a good idea.This should solve it,but as others have suggested,make certian that you have enough timing in the engine as well
Drilled the hole in the thermostat, LEVELED THE ENGINE, it was sitting higher in the back(sure that didn't help), all the pulleys are stock with the engine, running at 4 degrees advanced. The next thing is to raise the radiator about 4" before I try to run it again. I will post back with block and head numbers, and any success, thanks for all the help, you guys are the best.
Your timing might want to be around 12.
Success.... Most of the problems I was having was my own fault, leveled the engine on the stand (1/2" up in the back) raised the radiator up about 3" and drilled a small hole in the thermo. Now its running between 195 and 205 or so which I would expect due to it's new, the radiator is just 2 core and I have an electric fan but that's only temporary until I get it in the car in the spring, I can't thank you enough for the posts to help me get my head out of you know where, you folks are awesome.
You're average @ 200 degrees isn't unreasonable,but the bigger the cam,the more inital timing you're going to need to get it closer to what you want.I wouldn't think that when on the stand,with no load on the engine ,that a two row radiator is a problem.