crank shaft

Can somebody tell me what the over sized piston decimal counterpart is on a overbore 455 block? I know 4.126 is stock, 4.155 is 0.30 over what would 0.40 and 0.60 be? I was also wondering if someone makes a set of 0.40 flat top piston kit?
Thanks, Mike

MDchanic

Are you asking about arithmetic?

4.126' + 0.030" = 4.156" (or 4.155" - the exact bore is always determined after measuring the actual pistons)

4.126" + 0.040" = 4.166"

4.126" + 0.060" = 4.186"

- Eric

crank shaft

Yes I was. Thank you, I was thinking of it a little differently. I just sent a block to the machine shop and I think there going to have to take it 0.010 over and it at 0.030 now. Do you know if anybody offeres a set of 0.040 over pistons for a olds 455?
Mike

MDchanic

Speed-Pro's got 'em, and I'm sure there are others as well.

- Eric

crank shaft

I will look, Thanks Eric!

Sugar Bear

"the exact bore is always determined after measuring the actual pistons"

This is critical, find out exactly how much the machine shop needs to bore, get the size pistons needed or have the machine shop supply them. After the machine shop has the pistons they should begin the boring/fitting process.

Did you send them the block only or the pistons and rods? Asking this because the pistons can easily be put on the rods 180 degrees out. Take pictures before removing the pistons from the rods, number the pistons and rods, go slowly, and press them back on the rods positioned properly.

crank shaft

Yes I did send them the rods, pistons, crank and block, My machine shop says it will need to be bored to 0.060 over due to the pits in the cylinder. There going to take this think one step at a time. They think it was a drag engine that was taken apart and set for many years.