I bought a '68 GTO clone, made from a LeMans. It is supposed to have a 400 engine in it but the guy who built the car is deceased. The engine code stamped on the right, front of the block is Y4 but my '68 shop manual only lists codes consisting of two letters, no numbers. Maybe an engine for a different year? Who knows? Thanks, Scott Jones

 

Scott, Thay are 5 engines using Y4 code, Here are the 400 years 73 with 4x heads 170-185 HP, 1977-400 with 6x heads-180 HP. Three 455 with Y4 codes- 73-74-76, If you can give me the unit #s near the distribor (SK) thay are at the back on top of the block. All of the #s Posted are from a Auto Trans.