so ive been reading about how much a block can be bored,my question is what would be the minimum thickness of a cylinder wall,not a race motor,just a everyday grocery getter type car,how thick is the average wall on a new standard bore engine,be it mopar,chevy,ford,etc
i had a john deere mower with a 14 horse kohler that somone had bored so much that they cut clear thru the cylinder and the cooling fins was the only thing holding the cyl together!!

I would not feel very comfortable with less than .150" on a mild performance motor.

Average thickness? all over the place, only a sonic check can say what you have. Best plan is to bore minimally on anything other than an all out race motor. .030" over is usually the recommended max and I would not exceed that without a sonic check.


Some info

http://arengineering.com/tech/sonic-checking-the-mopar-big-block/

Good luck finding a BBM with that. I have 6 blocks here, all have cylinders under that at .030" over.

I've sonic test a lot of blocks and the thickest I've tested were 76-78 blocks. Some of those had .200 after a .060 bore.

Going out on a limb here..................

Major thrust - 0.150
Minor thrust - 0.120
Sides with no thrust - 0.090

That'd be for a grocery getter every day motor.

R.

Those are good numbers after boring I've owned a Dakota digital 1000 sonic teter for a long time now and I've used those numbers on mild 360 LA bracket motors(11.5 to 1 compression) where the owner only had that block and insisted on building it, it is still together today as far as I know with a lot of runs on it, 500+
One of the former NHRA stock World Champion 428 Ford racers said that they use .090 as the cut off on the thrust surfaces on those blocks