davepl

That was my conundrum. I bought an L36 427/390 car out of a barn (not a Vette) and the last thing they did was rebuild the motor. Punched it .030 over, new pistons, box of receipts, the whole deal.

But they couldn't be bothered to put a baggie over the carb. And over 20 years, a drop of water a week from condensation adds up.

Long story short, we had 7 very nice holes and one big mess. I'm hoping going .060 over will clean this up (and that 3963512 castings are good for that).

Looks like my block has one lifter sleeved from the factory as well. Not uncommon I'm told.

lars

Why don't you just sleeve that one hole to take it back to .030 - that would allow you to retain all the pistons - replace just that one if it's pitted beyond salvation. Give all the bores a fresh, light hone, slap new rings in it, and you're set to go at a fraction of the cost of boring the whole thing .060. If you really want to bore all 8, just go .040 rather than .060.

Lars

Dynra Rockets

just you :-)

Big blocks use symmetrical valve placement (look at the even spacing of the header tubes). It is ieieieie.

HeadsU.P.

Ok, thanks. Question deleted.

davepl

I normally do all my own motors, but I know a retired Winston Cup builder that's in the area, so I'm letting him do it while I stand there and ask a MILLION questions. It's been great. Did you know the distributor tower height changed at the same time they moved the date code to the bell housing on these motors? He seemed to! But I knew what "CONV" meant (conventional fuel, ie: not diesel) so there was that.

I don't know if it'll clean up at .040. If it does, great. Less is more in that regard.

I was just thinking about the sleeve idea today, actually, but haven't had a chance to ask him about it. Since they appear NOT to have balanced the assembly (no grinding on the rod pads anywhere) about all it'd save me is piston cost.

He also suggested we line hone the block. He showed me the wear pattern on the mains just from whatever hand rotation it's had, and it was uneven.

If you were a buyer of a 427/390 Corvette, would you prefer one that's .060 over or .030 over with one sleeve?

Big2Bird

.030" over. Hands down. That would give you another rebuild later.

Dynra Rockets

.060" over is a pretty big cut. Are you sure it needs that much?

427Hotrod

I've never seen a lifter bushing from the factory. Someone did that at a machine shop.

Can't really tell...but you might be amazed at what a good deck plate hone can remove/clean up. It wouldn't even bother me to bore one cylinder a little larger and leave the rest alone. Maybe one custom piston with a little extra diameter...or even some of the new piston coatings can take up some slack? It will still balance and you'll never know it has a hair more compression.

Otherwise .040 or .060. Odds of it ever needing another rebuild is slim based on how most folks use them. And if something bad happened you could always sleeve that one cylinder. Old blocks can often go .100-.125 over with a sonic check.

I think most folks would be more concerned about a sleeve thinking it might have been cracked or something. But if you put a sleeve in it, that hole will be the strongest of all of them.

Are those forged pistons? They don't look plain cast and if it was 20 years ago not likely to have been hypereutectics....but maybe?


JIM

Big2Bird

GM would have tossed it. Not worth the trouble back then.

gkull

I'm with jim or this idea. Hone the bad cylinder and see how the bore is pitted. Honing hardly changes the bore dia and in turn the ring end gap.

I saw a post on ring end gap and there was negligible difference between tight and way wider than normal on newly rebuilt engines during leak down and dyno testing. It is much different than a high mile motor where the rings face is worn, the bore is out of round and the ring end gaps of course opened up.

Pop Chevy

I also agree. Pull it apart and run a hone down through it, doesn't look terrible to me. But see how it cleans up. Are you looking to race it ?? If it was mine , I'd try to clean it up 1st, then sleeve one hole if it doesn't.

Big2Bird

How about the adjacent cylinder? (Close up).