I seem to remember a magazine article on it. I know all about sonic testing I'm just wondering how common it is to do. I've got a few 318s is all

I know one guy that did one keeping stock stroke and it lived in a race car(no street). And I know another guy that did one for a 4in stroker (sonic checked good) and a cyl wall failed first time he got on it.

I'd walk away from them.

one of my racing buddies has sleeved a 318 & made it into a 340. it's been going strong for years.

I believe member strokeraspen had said he had safely overbored his 318 .120 over...

I have heard of a few that have gone .100 over....those blocks were late 60's and only cast for like a year and a half.....don't have any casting numbers but I believe the years were 67&68......and this is hearsay...so

Rickster

Rapid might be talking about my motor I had, I think I got gypped by a lazy sonic tester

I only did it because of piston selection and the sonic test was "good" so why not. I beat the block apart witha hammer and most of the walls were VERY thick, one cylinder was not.

Watch your sonic test like a hawk or take it to someone you REALLY know and trust.

4.030" bore x 4.250" stroke here! I DID crack one block, but it wasn't from over boring, it froze over the winter. I had the block filled and the concrete must not have completely set. We had it happen to another one of our personal engines. It was an oldsmobile, same batch of block fill.

We have a few 318's out there with a 4.030 bore and a 4.25" stroke. One 318 is at 4.060" and a stock stroke, and it is about 20 years old now and going strong in an industrial application!

You need to use an old casting. We have used late 60's blocks.

Oh and forgot to mention, none of the current engine have block filler in them.