In the normal course of events I replace piston rings any time I pull a piston.
Maybe I shouldn't?
I'm guessing I've pulled apart about 50 V12s none have ever had a ridge in the bore from piston wear. I don't know what they use for Iron but it sure is dense. Or maybe they don't have a lot of ring tension?
I'm going to reuse the pistons and since they will be used on a supercharged application I'll need to open the end gaps up.
Will the engine rebuilding police arrest me if I reuse the rings? I already reuse bearings if they are still in good shape. I've never been it yet. Worse case I lose a few hours and a gasket set .
I'll need to re- hone the bores anyway so the process of reseating will be normal. I'm sure I can rig something up to check ring tension.
Sir the only thing that comes to mind here is if the ring is Impregnated with another /Chrominum/nickle in the outer edge or just all Iron, then you would look for a Shiny surface or just black gray of iron. Remember the old trick of using a Fish Scale to Pull the Piston w rings through the bore, 7lbs resistance is what we looked for after the gaps were set. And you know about stretching the ring open when they get removed, I stack all rings of each cylinder to see if one Has Gained more width than the rest.
In reply to GTXVette : thank you, no I'm not aware of the trick of measuring the pull of rings. It sounds interesting and a viable way of seeing if the rings can be reused.
I was thinking of looking at the ring and seeing if I noticed any wear. If the taper had a flat spot, that sort of thing. I had expected to study the face of the rings as well as careful measurement of them before I considered reusing them. But with 4 spare engines to pick and choose from plus all the parts sitting on my shelves I felt pretty confident I could put together a set worthy of re-using
If I don't have a complete set, would you consider using Perfect circle rings in a supercharged application?
I was thinking with it's two piece rings leakage wouldn't be as severe since you can offset the end gaps 180 degrees
I used to freshen up AMA Pro Sportbike motors for a winning team.
We almost never replaced the rings the cost/gain ratio did not compute.
If there is nothing wrong with the cylinder there is nothing wrong with the rings.
If you home and re-ring there is more wear.
If the cylinder needs rings it likely needs boring and a piston as well.
The chance of used rings failing is no greater than new rings given proper cleanliness and assembly techniques.
The piston grooves need to be cleaned out on the back side on anything with some miles on it.
Do this carefully and by hand so the ring grooves don't get gouged.
Also when the Shortblock is assembled do the math 7 lbs X 12 = 84 lbs + 5 for main bearing Drag = 89 So set your Torque wrench at 90 ftlbs and rotate the crank with your wrench It should not Click, A pound or two Either way would be ok Less is better. 15 more is probably too much..
In reply to GTXVette : that's the way I've always done it. Assemble the engine and turn over with a torque wrench I always use a beam wrench to see exactly where the highest torque is. It's a handy way to check for bent or warped crank/rods /pins etc. I also do it on the camshafts for the same reason. It shows sticky valve or bent camshaft etc I need to use an inch pound wrench for that though
I sure like the idea of pulling a piston through the bore to measure ring tension. The simplicity of that approach sure beats my idea of making a jig to check ring tension. Thank you
hopefully my numbers were correct for you.
If everything is in good shape, not burning oil, etc. I don't see why you couldn't reuse them. I'm not so sure about full blown mix and match though, seems to me it'd be best practice to keep the rings in the hole they came out of.
In reply to BrokenYugo : As soon as you pull the piston out of the hole the micro grooving will no longer line up so you may as well take the best 36. I have to pull the rings out to open up the end gaps for supercharging .
Likely there will be some minor surface rusting since some of these engines have been sitting in the shop for decades. I'll need to do a light honing to remove that.
Right now I'm torn between using the later high compression pistons with the bad flowing heads and using the low compression pistons and the great heads. While there is 42 more horsepower with bad heads/ high compression that's at 4800rpm
since the stock cams effectively limit rpm to 5500 that makes sense. However if I regrind the camshafts to raise the peak rpm to 7000 there is 120 more horsepower with the good heads and low compression.
The factory took a stone stock engine up to 7800 rpm with any signs of valve float so I am confident I can do it safely
In reply to GTXVette :Well I can do a little math. Since those are for a V8 I only need to multiply times 1.5 to get a twelve. With it's short stroke 7 mains and really giant sized bearings I'll adjust accordingly. I keep all those numbers in my build book.
My Number was for 12 cylinders but only 5 Mains So 91 ftlbs.
In reply to GTXVette :yeh, I reread that after I posted. But I still like the idea of measuring the pull of a piston through the cylinder as a way to check ring tension.
I wonder if I've got a set of new rings around still as a baseline.
Glad you like that. Use a lite lube like wd40
