Just got the info back from the machine shop. My block is standard bore, will need 40/60 taken off in one hole or a sleeve... Considering taking them all out .0625 and getting standard HC 425 pistons... Looking for any feedback from anybody that has done this. There are pros/cons available on the net... Trying to decide.

 

Get it sonic checked first.

 

.0625 won't get you to a STD 425 bore. You will need to go .125 Like Mark said you should get a sonic check first but I doubt you will have any problems, the 400 B blocks are usually pretty thick. I have a 400 B block in my '65 that is .155 over and the guys at the shop that sonic checked it couldn't believe how thick it was. At that point you may as well put a 455 crank in it like I did and make it a true 455. You will have better piston selection that way as well.

 

It's pretty common to use std bore 350 Olds pistons in an early 400 block. Compression height is the same and the 4.057 standard bore piston is an 0.057 overbore in the B block.

 

[QUOTE=chadman;614727].0625 won't get you to a STD 425 bore. You will need to go .125 QUOTE]



Sorry I was speaking in terms of radius, not diameter... Will only be removing .0625 from the wall to get to the overall bore of 4.125


Thanks for the input!

 

Machine shop wasn't quite sure that .060 would even get the pitting removed. So we started talking about taking it to a 425 which has more readily available parts... I

 

I definitely will be doing so before we get too far into this thing. Thanks for the advice

 

Well, you can get 350 pistons in STD, 0.030, 0.040, 0.060. etc. I just think 350 Olds pistons are easier to find than 425 Olds pistons, but use what you can get. The 350 piston gives you the option of going 4.087 (or 4.097, or even 4.117) instead of 4.125. Forged Speed Pros are $315 at Summit. Silv-o-lites are $204.

 

Thanks for the info. Will definitely consider this if the machine shop can clean up the holes.