maximum engine bore

[Gary W A]

I have a 318 I look to rebuild. After dismantling I noticed that the pistons are stamped .040. Leading me to believe it has been bored 40 over. I have researched ways to rebuild it to mildly increase it's horse power. Several articles strongly suggest to not have a block punched more than .030" over. How critical is that? The block is a 1970. Thank you.

 

[273]

Its fine, build away.

 

[rumblefish360]

Max over boring is determined by a sonic check from your machinist. Cylinder wall thickness is the key. Not how much it is overbored. That suggestion was probably made before inexpensive sonic checkers were made and the average or even above average builder could not afford one.

Give the block to your machinist and have him check it. If he doesn’t have a sonic checker tool, a new machinist is in order.