F-2 Speedy

13 year old thread 252

Robs 252

yes...

F-2 Speedy

is your question about mixing internal external balanced parts ?

Robs 252

Both the motors are gen 6, so I believe they are both externally balanced.

F-2 Speedy

whats the part # on your flywheel

Robs 252

Not sure. It came off my gen 6 454 that had cast internals, and was installed on a new 502 long block, that has forged internals. I don't notice much vibration, but I'm wondering if its ok to leave as is..

BillK

Yes but the steel crank uses a different flywheel than the cast crank.. The balance is different. Not much but it is different. It might be enough to affect bearing wear in the long run, especially the rear main. I have the exact specs at the shop in my balancing files.

F-2 Speedy

Im not 100% for sure

BillK

The cast crank flywheel is 42 oz-in out of balance. The forged crank one is 42.5 oz-in. The .5 oz-in difference is about the same as 7 grams on a typical big block crank counterweight. Is that enough to cause a noticeable vibration ? Probably not. Is it enough to cause long term bearing wear ? Who knows

To be honest with you it probably is no worse than your typical Big Block truck engine is from the factory. But those engines lumber along at 1800 rpm most of the time.

Robs 252

Thanks Bill, I appreciate the info. Based on this, I think I'll leave my original flywheel installed as is.
I'm not a mechanic, but it seems to me that the specs are so close that they are almost in the range of manufacturing differences?

Thanks again..