69-er

I have an old SBC that is maxed out at 0.60” over. It has about 70,000 miles since it was rebuilt. Several thousand miles ago, I tore down the motor and did a quick hone and ran the motor with no apparent blow-by problems. (On cold mornings, it does sound like a diesel! Piston slap?) I can’t remember what type of rings I used.

For other reasons, I have torn down the motor again and I’m going to try to do a hone one more time. I have no idea what the actual taper is. There is very slight ridge I can feel, with the sides of the cylinders being a little less, so I know there is an out-of-round condition. I can still see a lot of the original cross hatch on the walls, but the pattern is irregular and somewhat patchy.

Since this is not the correct way to be resurfacing the cylinders, I was wondering what would be the best ring to use that could tolerate the irregular wear.

Atilla the Fun

60 over is NOT maxed out. JE Piston does 65 over, and 70 over. By the way, a 4.070" bore is a 30 over Mopar 340, so you have lots of choices for rings, while at 65 over, you'll have to do JE's rings, or use file-fit rings minus the filing. If that's not in your budget, 80-over cast pistons and cast rings are readily available. They're all dished, there are no 80-over flat tops. But it would be cheaper and easier to just get another block that's already been 30 or 40 over, and make it a fresh 60. Really, you can get a good 350 block for $100 anywhere, they're not scarce nor difficult to get. That would save you the pistons, rings and re-balancing.

tom3

The cast rings are probably the best way to go. Molyfilled rings do require a near perfect bore and pretty exact finish to get a good seat, but they last much longer when right. In the older bore I'd go with cast though.