i have a '91 Corvette L98,

according to GM, the early style sbc flywheel has a 3.58" bolt circle diameter and the later style is 3". is this the diameter from center to center of the bolt holes or from inside to inside or outside to outside edge?

i have a flywheel that measures ~3.5" center to center and ~3" inside to inside so depending on where the circle diam. is measured will tell me if it's the early or later style and whichever it is, i need the other for my engine because this flywheel wouldn't fit on the engine.

i *should* need the newer style flywheel because i have a one piece rear main seal block but i just want to make sure because despite it being a '91 it came with the early style heads/tpi from the factory and i want to make sure this isn't another corvette-ism.

 

bolt circle is measured from center point to center line of bolt holes. you can tell a late flexplate by the bat wing weight and they have a dowell hole along with the bolt holes.

 

are the new and old style supposed to be the same thickness? my new style centerforce dual friction flywheel is a bit thicker than the old style but i think that's just because it's for a not OE type clutch.

 

far as i know the only differances are the balance due to the lose of the flange weight on the end of the crank when they went to the 1 piece seal and the addition of the dowell hole so you get it located correctly to balance the crank