Just making the choice between cast and moly piston rings. How much wear considered too much in a 225 bore to take moly rings?
If the engine is within factory specs (I think 5 thou out of round, 10 taper) can you use either, or does this only apply to cast rings? If so what would the sensible specs be if using Moly.
The engine will be almost standard, not used for racing, in a car and will spend most of the time doing longer runs cruising between 2000 and 3000 rpm.
I know re ringing a worn engine is at best only a temporary solution, and may or may not be successful.

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1967 VC Valiant

I'd save the money and use plain rings. Hasting has good information.

https://www.hastingspistonrings.com/tec ... mendations

Every slant six I've torn down has needed a re-bore.

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Joshua

Yes good link Joshua thanks, however it does not mention how round and parallel the bore has to be to have a good chance of moly rings sealing.

I would prefer to use Moly, but I know if I prep right and use good cast rings I have a high chance of success. I don’t mind paying extra for the moly rings but don’t what to have very low chance of them working.


Anyone else got specs, links, success or unsuccessful stories about what they have done with re rings using moly rings. I have read lots on them about having to have a fine hone finished bore, but I cannot conclude whether this translates to having to have perfect parallel bores, or whether it is only to stop the moly from being chipped off during break in.

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1967 VC Valiant

Moly rings require a near perfect bore as far as taper and out of round goes. They just aren't as forgiving as cast rings.

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There's no such thing as too much cam....only not enough engine!

I just bought a set of sealed power pistons from Summit for $68
http://www.summitracing.com/parts/slp-244np20

With slant six pistons as cheap as they are I just can't imagine a situation where I would try to re-ring a block with worn out bores.

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Thanks Precycle, I did see those slugs too, and could be the way I go. My bores aren’t exactly worn out, just not new anymore. Once I make the decision to rebore, I know I will be suddenly spending on everything, it won’t be a case of take a chance on the rest of the things, so it will be crank grind and bearings, camshaft, and oil pump, water pump, radiator.
At the moment, I can do all the work and it will be the cost of the rings and a few gaskets, and I’m confident the rest of the motor will see out the life of the rings. If it doesn’t work, I haven’t really lost much.

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1967 VC Valiant

with iffy bores I have had the best luck with Deves rings.Call 877 338 3722 and tell him Mark from Moto Guzzi Classics recommended him.