305 to 350 bore


Junior Member
Amarillo, Tx
Okay, here's my question. I stumbled upon a 305 for free. I really wanted a 350 to build up, but with a free motor you can't expect much. I know the stroke of a 305 and 350 are the same size, there is a .236" difference in bore. Could I buy a 350 rebuild kit and bore out the difference? If so, how much would it cost?


Senior Member
Double check that your heads will work with a 350. About 7 yrs ago, I replaced the 305 with a 350 in by K5 blazer. I don't remember the reasoning, :confused: but I had to get different heads because the 305 heads would not work. Something to check.

That's WAAAYY too great a difference in bore sizes. You will definitely hit water if you try to bore it that large.

In fact, I've had a couple of 305 blocks that were junk after a 0.060" overbore (they were checked with a sonic checker).

Why not sell the 305 block and buy a 350 block? Since both engines are extremely popular, there's no reason you shouldn't be able to buy and sell for exactly the same price, so you'll still have a "free" engine and it'll be a 350.


Albemarle Lawn

Junior Member

You paid exactly what that 305 is worth: $0

Maybe you can sell it for a profit for $50.00, if you find a sucker.

There are plenty of cheap 350's out there.

And, IMO, the best deal is from GM: Brand new 4-bolt 350 for $1299 from Sallie Chevrolet or Scoggin-Dickie.

Both of these dealers have websites and ship nationwide.


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