GTR1999

Looking in the Summit catalog at B&M convertors for a TH400 they mention a dual bolt pattern flexplate or small pattern required. How do I determine the type of flexplate I have and need? This is the original flexplate I have.
Thank you,
Gary

442olds

one way to tell is the bolt orientation of the starter bolts. I can't remember which way it gos right off the top of my head but there are two basic bolt patterns for a chevy engine. two in line or two with one forward on the block. I think the one that is offset is for a smaller flywheel but I can't remember for sure. Otherwise you need to either meausre the diameter of the flexplate, or count the teeth. 153 (small) 164(large).