.060 over bore OK?
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Senior User
Joined: Jan 2003
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From: Calgary
.060 over bore OK?
There is a guy in the local paper with a '68 302 block that has been bored .060" with pistons, rods etc for sale. Is .060" over bore too much? Would I be asking for trouble?
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Hotshot
Joined: Jul 2002
Posts: 14,285
Likes: 12
From: Bend,OR
if it ever got hot it would be a done motor thats for sure. also that says 1 of 2 things, either that motor has been rebuilt many times or it had a major cylinder issue which required it to be bored out that much. 302 blocks are plentyful so i would pass this one up in my mind. I have 2 that are stock but live a bit far unless you payed shipping
Hotshot
Joined: May 2004
Posts: 12,170
Likes: 5
From: The hills of No. Calif.
.040 is considered the max safe overbore on these blocks. Some people have found that by sonically checking the block for core shift they can go to .060 but your cylinder walls are very thin by that point. I agree with Kemical, these blocks are so common that it's not worth the risk.
Hotshot
Joined: May 2004
Posts: 12,170
Likes: 5
From: The hills of No. Calif.
Yes, but I've never heard of a '68 block punched out .060 over before. Those cylinders must be perfectly centered, and even so I'll bet they're paper thin. They probably flex from the pressure of the rings passing over them!
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