hey guys, so i have been working on my 69 350 for awhile now, and the bore ended up being only about .015 over instead of .020 over (i have .020 pisons to go in). so we tryed recalibrating the boring bar and boring again, the piston fits in, but its a little loose. the ring end gap for the top ring at about 2 inches from the top of the bore, is .020. is this ok since the piston fits decently, or should i go to .030 pistons and .030 bore ? im planning on drag racing the car every once in awhile. thanks a lot

 

Been a long time since I've delt with piston engines to that extent. .020" seems kind large to me, If it's too gapped you'll loose compression and use oil, also run the risk of breaking it, I am sure someone with more knowledge can post.

 

What brand and type off pistons? KB pistons take more gap than that on the top ring.

 

Take the pistons, along with the block, to a competent machine shop.

They will be able to correctly fit each bore to an individual piston, using a power hone. This will eliminate the "can of worms" you are about to open.

Norm

 

The cylynders should be honed even after boring them. Good point

 

they are federal mogul pistons, and rings. the only number i have been able to find in a book, is the ring end gap cant be any less than .015. and small block chevys are all .010 to .020