305 balance job

[Bobby Zlatkin]

I know 400 small blocks & 454 BB's are externally balanced.

However, I acquired a balanced, 305 (1 pc. rear seal) rotating assy. & am very uncomfortable with the flexplate. It has a rather large, horseshoe shaped, weight welded to it. Can this be right?

What about the dampner? Is it neutral balanced?

[Lew Silverman]

Bobby,

Any numbers on the flexplate? It's unusual for an internal-balance SB to have a weight on the flexplate/flywheel, but some after-market "heavy-duty" unit's may need them. Is there a lot of Mallory metal in the crank?

Just a thought..........

Lew

[Leon Rennebaum]

All one piece rear seal cranks are externally balanced at the rear - the round flywheel mounting flange, that the one piece seal must slipover and seal on, prevents the counterbalance from being part of the flange itself. Therefore, the counterbalance must be placed on the flywheel (unless the crank is specially balanced aka Mallory Metal). The front of the crank is internally balanced like any two piece rear seal crank.

[okieracer]

Originally Posted by Bobby Zlatkin

I know 400 small blocks & 454 BB's are externally balanced.

However, I acquired a balanced, 305 (1 pc. rear seal) rotating assy. & am very uncomfortable with the flexplate. It has a rather large, horseshoe shaped, weight welded to it. Can this be right?

What about the dampner? Is it neutral balanced?

From the factory, one-piece rear seal 305 and 350s are internally balanced in the front and externally balanced in the rear. Unless the crank has been internally balanced in the rear, the flexplate should have a weight on it.

[Bobby Zlatkin]

Well, I just learned something. Thanks guys. It makes sense about the round flywheel mounting flange preventing rear crank counterbalancing.

Not familar with this late model stuff (Ha Ha, mid 80's considered late model).

So, I assume, an aftermarket SFI balancer for a sbc would be good to go as is.

[rustbucket79]

Originally Posted by Bobby Zlatkin

Well, I just learned something. Thanks guys. It makes sense about the round flywheel mounting flange preventing rear crank counterbalancing.

Not familar with this late model stuff (Ha Ha, mid 80's considered late model).

So, I assume, an aftermarket SFI balancer for a sbc would be good to go as is.

You are correct, any neutral SBC balancer will do the trick. As always, get the correct timing tab for the balancer, GM used both the vertical (behind waterpump) and offset to the driver's side.