The Stovebolt Site Forums The Shop Area Engine Shop Max overbore on a 235?

I'm contemplating a '48 235 rebuild .

What max overbore is normal for this engine .

Thanks for your time

http://chevy.oldcarmanualproject.com/shop/1948_51truck/51ctsm0624.htm

Shop Manual says 0.040" oversize, but, I have seen people post that larger pistons are available and can be used. Someone will correct/confirm a max practical/available oversize.

Thanks Tim , that's what I was looking for .

I'm no expert by any means, but I have a 1955 235 bored .060" over. I found .080" pistons when looking to rebuild it and read about some.100" pistons being put in high performance applications, hut no one actually carried them.

1/2" over is perfectly safe, everyone says so.

I have a 1961 261 that was .060 overbored in 1972 (my second engine rebuild).

It has been back in my Suburban for about 10 years.

Millions of stovebolt engines have run for decades with .060" and .080" overbores. When boring a block for a sleeve, it's common to bore the cylinder 3/16"(0.1875") or 1/4"(0.250") oversize without hitting water, but an overbore that size would not be suitable to run a piston in. I have sleeved hundreds of cylinders without any issues, so it's possible to salvage a worn or damaged block as long as there are no cracks or holes in the cylinder wall in the top or bottom 1/2" to 3/4" of the cylinder.
Jerry

Mine's one of them (.080"). I will confess that before the rings seated it ran hot enough to make me nervous but settled down after break in.

Just following up on this topic. I was talking to the machinist that is boring my 235. It is currently at .030 over and now he doesn't think that it will clean up at .040 over so it would have to go up to .060. Has anyone noticed a power loss due to boring it that much? Would I get more power out of it by putting sleeves in it? I plan on running a cam from Patrick's in it with dual exhaust, 2 carbs, and HEI ignition.

You will be fine at 60. I would even go .080 if need be but not more then that. But at .060 you can find pistons and rings so good to go.

You will actually gain a little power at 60 over, due to slightly more displacement and more compression pressure, but it would take a skilled dyno operator and a fair amount of luck to actually measure it. Be sure your cooling system is up to dissipating the extra heat load the thinner cylinder walls will create. Installing a new water pump and a new or rebuilt radiator would be a really good idea.
Jerry

Thanks I feel a little more comfortable going with 60 now If it needs it.