When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Is the old GM 400 small block chevy with the 2 bolt mains internally or externally balanced?
Stock sbc 400 is an external balance motor ... meaning it has an external counterweight ... the 400 has external counterweight on both ends ... both damper and flexplate/flywheel are counterbalanced. You can internally balance a 400 and it still remain an external balance motor. Conversely, you can get a different crank for 400 that is designed to be neutral/internal balance ... both its damper and flexplate/flywheel are NOT counterweighted (as is a pre-86 350) ... but, as all performance motors should, it should be "balanced" and that is done internally at machine shop.