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How much can you safely bore a 427 over? I have heard everything from 60 to 125. I dropped a valve and scarred the cylinder wall. Thanks guys
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Re: boring over a C2 427
Bill-----
For all practical purposes, 0.060" is the limit. That's because I don't think you'll find any off-the-shelf pistons or rings beyond that size.
However, if you need a greater than 0.060" overbore to repair the cylinder, you can always sleeve it. I'd MUCH prefer going with a sleeve than attempting to overbore the engine greater than 0.060" and using custom pistons/rings. In fact, if you have to overbore it more than 0.030", I'd use a sleeve in the bad cylinder. Why bore EIGHT cylinders (you can't just overbore one cylinder and leave the rest as they are or with a lesser overbore) to 0.060" or greater when you can sleeve the one bad cylinder and keep the overbore to as little as possible?In Appreciation of John Hinckley -
Re: boring over a C2 427
Joe, dang you are fast. The problem is it has already been bored 60 over. But your suggestion to sleeve only one cylinder is probably the best for the integrity of the engine.Comment
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Re: boring over a C2 427
Bill-----
If it's already been bored to 0.060" and any of the other bores are worn to the point of needing an overbore at this time, I think I'd sleeve ALL of the cylinders back to standard size. This will be expensive, but if you need to have more than just the one cylinder sleeved, I think it's what I'd do.
This ONLY applies, though, if the block is valuable to you as a result of original deck stamping. Otherwise, I'd just find another block.In Appreciation of John HinckleyComment
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Re: boring over a C2 427
if it is a 4 bolt BBC you can bore all the way to .125 with no trouble as i have done dozens.you can get custom made pistons in any oversize just make sure to get the pistons first. if the rest of the cylinders are OK step sleeving one cylinder is the way to go but at close to $100/$125 a hole to sleeve 8 holes it would be cheaper to get a new block. also get the block maged because dropped valves can crack a cylinder wallComment
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Re: boring over a C2 427
Ok, let's see if I can explain this and make sense. The car had the same owner from 69 to 6 months ago..he died. The man must have recently had it bored; you can still see the marks from it. The person who bought it off the widow (the guy I bought it from) told me he removed a big after market intake and 1100cfm carb, put lower profile valve covers. I believe this caused the valves some problems. The inside of the valve covers are beat up. It was running rough when I picked it up...I can tell you every number, ever stat, etc.. but I had never really been around one. So I did not hear the problems. I believe the valve covers contributed to the valve sticking open..piston hits, drives valve through the head. Now, what that the seller did not tell me was that he also removed a nitrous system. The hookup is still there in the console (I did not know what it was). When I took it to the shop, they knew right away what it was. They said you have to give the cylinders more tolerance if you want to run NOS. As far as #s go, the block has the mill lines running front to back. I had the guy from Corvette Tech in PA on the phone today as I stood over the engine (stripped down) describing what I saw. He said if it had those mill lines he is very certain it is true to the car. The tranny also has the vin with no evidence of tampering. The car is old and dirty. If the seller was trying to be deceptive I think he would have went for a little more $. How much do you guys think a complete rebuild with one sleeve should cost? I know it is a wag (wild ass guess). Thanks you guys are very helpful. BillComment
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Re: boring over a C2 427
Since a midyear with an original 427 can reach $100,000 to $200,000 in perfect restored condition while an NOM will max at $75,000 (unless it is an L88), and your option is to throw out the original block, then there is no option but to rebuild it, costs or no costs.
If you get hit at $100 a hole, and you have 8 (might as well go back standard size on all) and then add another $3000 or more for rebuilding, you'd still be under $5000.
And that is a bargain for your original engine in standard configuration ready to drop into your car.
To me, there is no option. Either rebuild it and get it right so you have the original, or buy another to sit in it while the original lives in the corner of the garage.Comment
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Re: boring over a C2 427
I have gone through all those scenarios in my head. Know anyone in Georgia with that ability that you would trust? I do not have much room for error in that engine.Comment
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Keith Black pistons available in .070 and .100 *NM*
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