Thread: Boring a 425, how large can we go

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wellllllll---Buick? anyway, are all the pistons new? If so I would suggest maybe another block as you will have to have 2 different sizes of holes, and/or-----if new 040, you would have all 8 holes same size-------

However, if you are thinking about going bigger on those 3 holes-have it done by somebody with a Sunnen CK10 hone and go til holes are clean, check sizes, check availability for pistons same compression, cast or forged same as you have , balance, etc and finish to the size necessary--------

Originally Posted by jerry clayton

wellllllll---Buick? anyway, are all the pistons new? If so I would suggest maybe another block as you will have to have 2 different sizes of holes, and/or-----if new 040, you would have all 8 holes same size-------

However, if you are thinking about going bigger on those 3 holes-have it done by somebody with a Sunnen CK10 hone and go til holes are clean, check sizes, check availability for pistons same compression, cast or forged same as you have , balance, etc and finish to the size necessary--------

Jerry, it's a 425 Cadillac engine.... My bad for mentioning it. The only reason he'd do the three is to check the block to be sure it could even be bored to 60 or 80 because of the rust in those 3 cylinders. If it can be bored, all 8 would be done w/new pistons/rings/etc. The machine shop is the one the company that my son works at use's. They have been open for decades, do a lot of work for the Caterpillar dealer my son works for. Plus the guy he talks to is an older guy who knows his stuff. Walk in w/a part & he'll ID it w/out looking in a book..