What’s the best rings for a performance build that has a slightly worn original bore. It’s a standard bore 340 that we torque plate honed. Has a couple thou taper. Using up parts I have accumulated. Moly top? Non moly? I’m not used to builds like this. Napier second? I’m buying new so I want the best performance.

If it was torque plate honed how can it still have taper? It should be round and straight.
Doug

Would it make sense to use a power adder top ring to seal ot up? Hellfire, Mahle GNS, etc?

Plasma moly top, iron second with a standard tension oil ring

What Cab says, Total Seal Plasma Moly set

The main issue with a tapered bore is that the rings expand and contract as they go up and down the cylinder, take a piece of wire and bend it enough times and it breaks, the taper does not really affect sealing all that much unless super excessive. Ring breakage is what you need to worry about. And 90% of the wear will be in the top inch of the bore, so majority of the cylinder will be straight. I used to fix a lot of farmer overhauls back when I was young, where they just run a hone and installed rings, I used to pull the pistons out and just shake off the rings. I would use just a normal ductile iron moly face ring on a couple thousands taper. What I do is run a rigid hone down the bore a few strokes and all the wear spots in the cylinder will be easy to see and measure, out of round is what keeps rings from sealing, again easy to see and measure if you use a good rigid hone first. My quick and dirty rule is, if you can catch a ridge with your fingernail at the top of the bore, it needs to be bored.

If this is an accurate statement meaning 0.002" taper, there is no concern here unless this is a full race motor. When I had no bucks I've re-rung motors with 0.014" taper. They're not 100,000 mile engines but sometimes you do what you have to do. Cab's recommendation is what I would do.

Call or email Total Seal, they are glad to answer questions.

About a 3/4in to 1in area at the top of the bore wasn’t touched, didn’t want to hone it out since the piston to wall is beyond big. Used a dingle ball to touch it and then the torque plate hone after.

I think any ring you put in there will be fine. No need to overthink this. No need to spend a lot of money.

I did this last night before anyone responded. So I’m glad this is the consensus.

Thanks everyone