I'm building a stock L98 for a 1990 Iroc. Stock inside. I'd liketo know if I need to buy an internally or externally balanced flexplate. Also,does the same apply to the harmonic balancer? I found a stock harmonic balancerat OE parts HQs (oehq.com) for around $70. I believe all 350 are internallybalanced. Does that mean the flexplate and/or harmonic balancer have tobe internally balanced? Or neutral? Also, can you recommend a good combo?Thanks

 

The flywheel or flexplate for a 1-piece rear main seal 350 has a small weight on it to compensate for the changes made to the crank rear flange for the 1-piece seal. Damper is neutral balance.

 

Thanks for the reply. So when shopping for parts I should ask for an external balanced flexplate and neutral damper, correct?


Thanks

 

The terminology can get confusing. The technical hardliners will insist that the engine is internally balanced, even though it requires the small counterweight. In their mind, the flywheel is an "internal" part of the engine. Not sure what to tell you.

See this article for what is required:

1955-1996 Chevy Small-Block Performance Guide: Crankshafts Manual (Part 2)

This photo (in the middle) shows the "batwing" weight on a 1-piece RMS flywheel: