I have an engine that I am rebuilding for my 69 SS. The casting number is 3955272.The engine stamp is TO313YP, I have searched everywhere that I can, but can't find what the ( YP ) is for can you help?
Dale

955272 is a 1969 2 or 4 bolt 396ci

YP - 1969 396ci 310hp TH400 Truck L-66 10, 20, 30

So will this be a good engine for my 69 SS? How far can I take it?? It is a 4 bolt.

It's a 396. It's a great base to work with so take it as far as you want to. Find a reputable engine builder and let hime know what you want it to do. Does it still have the stock heads with it?

by the way TO313YP - Tonowanda plant March 13th build date

heads are casting # 3919840. They have been worked. I have taken over to my machist the best one in Oklahoma. You have to get in line for his work. I am shooting for some thing to drive & show. I also have an original GM aluminum intake # 3933163.

Sounds like a plan. Good luck.