Hi my name is Drew and i'm 17 and this is my first post on thirdgen.org. i have a '85 Firebird T/A with a 305 TPI engine. I was wondering is the 350 block was really bigger than the 305 block or if they were the same size just a bigger cylender bore. so if i bored my 305 how much would i bore it over to be a 350 or 383? would it be better to buy a 350 block or would my 305 do fine?

 

All small block chevys are the same dimensions outside, 350 has a bigger bore than a 305, and the 383 is 350 bore but with a 3.75 stroke.

Oh and cant bore a 305 to a 350

 

262-400 cubic inch small block Chevy engines are the exact same size externally (Also, the 400 and 383 modified engines are externally balanced). A 305 and 350 have the same crankshaft, however the 350 has a 4" bore, and the 305 cannot be bored to that size. To create a 383, you need a 4" bore (350 block), and a 400 crankshaft. Aftermarket "stoker" cranks can now allow 383's to be internally balanced. If you have hopes of 350 cubes or more, you're going to need a different block. I suppose you could stroke your 305 with a 400 crankshaft but it'd be an absurd combination and would not be worth the efforts.

 

It wouldn't be too bad putting a 350 in. It uses the same mounts and everything. Just need diff injectors, knock sens, and chip.