Hello,

I have a 1972 GMC Sierra that I need to rebuild or get a short block for. The guy I bought it from said that it has a 408 cid BB engine(402 bored???), but I cannot find any info on this. Is this just a 350 bored over? Or is there really a 402 BB chevy engine? I more of a ford guy so I don't know that much about chevy engines, but I love the GMC Body stye on this truck and I want to keep it. I may not have to rebuild it, but the oil pump went on me while I was on the freeway doing 60. I replace the oil pump but now it runs like complete crap. It misses all up and down the RPM range and just doesn't run right. So I am pretty sure I have messed up the engine. I don't want to upgrade anything, just replace the bloack or rebuild but my friend said it maybe cheaper to just buy a short block and just put on my heads, intake, carb, etc etc. Any info would be great.

Thanks, Patrick

 

It's a big block chevy.

396 was made from 65 to 69. Chevy bored it .030 to make it a 402 around 70, but kept calling it a 396 for marketing purposes. So it could be a 396 bored .060, or a 402 bored .030. Doesn't matter, physically the same. Just use standard big block rebuild parts.

One caveat: Chevy also made a 400 small block, but bored .030, it's a 406. Small blocks have 4 bolts on each valve cover, big blocks have a bunch more.