Senior Tech Team
Join Date: Sep 1998
Location: Mustang, OK USA
ALL SB(except 400) & BB (except 454) flywheels are "neutral" balanced. SB400 & BB454 flywheels have, as has been mentioned, an additional counterweight.
If you are building a 400 or 454 and DO NOT have the counter balanced flywheel, you have 2 choices. You can pay extra to have the engine INTERNALLY balanced, or, you can use a large diameter (14in) flywheel (these flywheels are common) and have additional weight REMOVED from the opposite side.
Now, if you have a 400/454 flywheel and are building a 350 or 427BB, DO NOT use it and have the counterweight removed! These flywheels are somewhat scarce and you need to save this flywheel for use on a SB400/454BB----------------or sell it to me.