I have read that the 330 has a very thick sleeve and can be bored to .120 over sometimes with a sonic test, I have also read that the it could be over bored and use a set of early 400 pistons to build a 340. Any one else have any experience or know someone that does??

 

Most early Olds blocks do have thick walls, but a sonic test is definitely required. Of course, by the time you find (and pay for) a set of early 400 pistons, have the block machined, and have the crank rebalanced, you could have easily just built a 350 Olds with readily available parts. The forged 330 crank drops right into the 350 block, though you will likely need to have it balanced also if you go this route.

 

Thanks but I have a #'s matching 65 and I'm not going to loose the engine after it's been it's been with the car for 45 years.
I want to overbore it when the time comes. Maybe I'll have to have a set of pistons built down the road.