# Can 428 be bored .060 over?



## jtwoods4 (Dec 22, 2011)

I am considering purchasing this vehicle on ebay

Pontiac : GTO Pontiac : GTO | eBay

The sellers says the 428 is bored .060 over. Can you buy pistons for a 428 bored .060 over? Is is ok to bore this much on a 428? Will the engine over heat or will you have to have custom pistons made. 

I am concerned about the quality of the engine build.


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## geeteeohguy (Feb 2, 2008)

.060" is considered the "last" overbore size on a Pontiac engine. Most go .030, then .040, then .060. I like to go as little as possible...in .010 oversizes if possible. This isn't as impractical as it once was, because custom pistons are now readily available in any size. In big journal blocks like the 428 and 455, it is important to have them sonically checked out to determine the thickness of the cylinder wall castings before going for a large overbore. They can get pretty thin due to core shift while casting, overboring, or corrosion in the water jacket. A .060" overbore will need to be sleeved if it is to be rebuilt again...very expensive. But, to answer your question, yes, 428's can be and sometimes are bored to .060" to clean up the cylinder walls sometimes.


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## Tambo (Aug 15, 2011)

I notice there is no mention of the subject of rust in the ad. If it hasen't got any then its usual to state this. Also there are no underside pics and there's flaking under the paint in the pic of the tag. Be careful.


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## BearGFR (Aug 25, 2008)

Lot's of clues in the ad that worry me... like use of the term "big block", mention of all the stuff that either is disconnected or doesn't work, usage of a 68 ram air system, not a 69 --- all make me tend to think it was just thrown together by someone trying to make a fast profit.

Bear


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