Has any one sonic checked a stock 340 block to see how big of overbore a 340 can take? I have seen blocks bore .060 over to 4.100 Has anyone gone past this to 4.125?

Sonic testing only tells you what that individual block can go out to; if you're planning a max bore you'll need to test the block you have in mind.
Stiffer walls make more power than the last .010 or so you can cut away.

I plan to have any block I overbore past .030 sonic tested.

My question is if going past 4.070 is a good idea. If someone has sonic checked a 340 block I like them to post their findings. We could all use this information as to what is a safe overbore for most 340 blocks.

back then 40 was the most...but with the new r blocks u can go more

as big as the sonic check allows you to........
I just had my 1971 360 block sonic checked for the second time (from a different party than the first time) because the numbers first time around came in a little too good to be true, block was already punched .040 over in a previous rebuild, but thrust surfaces still range from .200 to .350 yet........