I just bought a chevy truck. The guy I bought it from bought a 400 for it and put it in the truck. I had to put a new oil pan on it today so I was also cheching to see if the guy was telling the truth. Well he was partly, it is a four bolt main like he said and does have a new 400 flywheel but the motor isn't a 400. The engine code is 3970010 which is a 350. Also I had noticed that the crank had holes drilled for balancing which i didn't believe 400s had because they and externally balanced. Anyways will there be a problem with the 400 flywheel bolted to a 350.

 

Are you sure that it may not be a 383 ? Does it have any motor shake? What type of harmonic balancer is on it (internally or externally balanced)? If it's a 383 and has an externally balanced balancer & flywheel/flexplate then your fine. If it is a 350 with internally balanced balancer and externally flywheel/flexplate then I would change it. I know someone who ran a stock 400 with an internally balanced flexplate...it eventually seized.

John

 

I'm not sure if it's a 383 but I don't believe so. The guy that owned the truck was told when he bought the motor it was a 400 and therefore bought a 400 flywheel. The balancer is interally balanced i believe

 

a 400 is externally balanced, namely one the flywheel and dampner. a 350 is internally balanced, neutral balance on the dampner and flywheel (excluding bat wing weight)