Weighted or non weighted flywheel

[primered_junk]

Originally Posted by WIDESIDE72

I just learned that the 87 up motors are externally balanced like an old 400. I buddy bought a Ramjet 350 crate motor and he had an external balance flywheel Jeg's recommended. I called them to be sure, then did a little research, and it is in fact external.y balanced. Why did GM decide to go external balance again? I thought internal was better. I know it was probably economics.What changed on a 350 that it was cheaper to balance external?

They went external due to economics, contrary to popular belief, the 305's had a different crank than the 350's, they had the same stroke, but had different counter weights on the crank, and old style 305 crank in a 350 or vice versa will cause a nasty vibration if the rotating assy was not balanced before it was put together. They found a neutral balance for the two and made one crank.

[Green Machine]

87 up 305 or 350 with one piece rear seal, use a weighted flywheel, because the rear of the crank is round, no place to put a weighted flange like the older cranks.