Thread: Boring a 425, how large can we go

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As some of you know I have 1979 425 that was rebuilt and bored 40 over. I sent it & my project truck to a shop be installed & assembled. Now I have a $5000 paper weight because the engine/trans & frame was outside improperly covered when it rained, got water in the cylinders and rusted 3 of them pretty bad. How large can a 425 be bored out??? I thought I had read somewhere they could be taken to 100-125 over. But I could be mistaken. The machine shop said it would machine the 3 worse cylinders to see if they can go 60 over. If not he'd have to take it to 80 over if it could be bored that big. Can the 425 be bored out to 80 over?? And if so is there any negatives, like running hot or any other things.. If its throwing good money away I need to know so I can find another block for the rest of the parts in it. The ONLY reason I am trying to save this engine is it was a Father's Day gift to me from my son the year he joined the Marines about 12yrs ago before it was rebuilt.

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..

Worst case scenario, maybe he can sleeve those 3 cylinders if they don't clean up at .060, and then he can bore them all the same.

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Originally Posted by 40FordDeluxe

Worst case scenario, maybe he can sleeve those 3 cylinders if they don't clean up at .060, and then he can bore them all the same.

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YEPPP, that's what we decided to do. After talking to a Cadillac Performance guy yesterday he suggested to sleeve those cylinders. He said since its only 2 or 3 cylinder just have the machine shop have them bore it out & put a sleeve in it so we can use all of our new parts still. He told me it should be a heck of a lot cheaper then having to buy a $5-600 set of pistons.

PLUS, while looking for another block my son Joe,Jr came across an ad on Craigslist. A running complete 425 w/transmission for $125.oo. Yep you read that correctly. An older woman had it for her 50 Buick but decided to do something different. So he went and got it. We figured that if we didn't use it in my bus we'd shove it in an S-10 or something odd just for sh1t's & grins..

Thanks everybody....joe

That's a good deal on another engine and trans! How's the rest of the repairs going on Large Marge Joe?

Originally Posted by 40FordDeluxe

That's a good deal on another engine and trans! How's the rest of the repairs going on Large Marge Joe?

That was a great deal on that engine & transmission & w/in 4 hours of being on line we bought it
As far as the rest of it, Joe's taking everything apart because I don't trust NOTHING that POS did to it after seeing it. Joe's took the block completely apart & has started cleaning all t he internal parts up to be re-installed when the block is done, removing the brakes & rotors to clean everything up, opening up the rearend to see if anything is wrong with that. He gutted the interior & got rid of that garbage interior that was in it. My son sews better then the interior guy PMK use to put that trash in my truck. We're taking it off the frame again & will either do a straight axle, a frame clip or what ever I can find that will work on a 3/4 ton Chevy truck frame. I would do a frame swap but really don't want to unless it would save us LOTSSSSS of time, trouble & headaches. Most are too wide by about 2-4 inches and I really don't want to widen the fenders unless I have too, but who knows what may happen.

My word of advise to anybody is don't ever have work done or buy anything from PMK aka PurpleMonkeyKustoms. After seeing what I got, what the other 3-4 people who contacted me got & what I seen in his shop the very few times I was allowed in I wouldn't let him work/paint a tricycle for me. I tried for the first 6 months of the year to try & get my truck back & he'd either tell me he's going to work on it or would ignore me. If he hadn't dumped it in the yard that day, we had made plans to show up w/some friends who were Police & Veterans to take it. And my son in 11th grade did better body work & paint then what myself & others got when we got our trucks/cars back from that a$$hat...joe

Ouch. Bummer.

Originally Posted by firebird77clone

Ouch. Bummer.

Yeppp, but honestly I'm not letting it get under my skin... KARMA is a B!tch and I told him for months that if he didn't get it done soon that Denise would haunt him. From what I have heard both them ladies have visited him a time or two

Glad to see you're pressing forward with it, Joe.

Karma will win out in the end, Joe. I had an experience similar to that with my boy's '68 Torino, barely escaped jail for trying to extract the shortcomings from the guys hide, and lost a couple of grand in the process. But, a year or so later, he was in the news; lost is shop, business licenses, house, and a collection of over fifty classics and muscle cars, and he just vanished.

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