Where's the best place to buy a Big Mig 061? The ones on eBay are all nickle plated.
I don't think any of them are nickle plated, unless someone ground off the aluminum oxide and plated it. Even had they, I doubt it would make a significant difference in the results.
Note that the passage from Norvel that Fred quotes contains several misleading items - all slug-piston engines rely on the same principle to seal, and none of them run significant metal-to-metal contact, or at least, not for long! There must always be a oil film separating the parts, if you don't, you get the problem in the other thread - turn the engine over slowly, particularly with no glow plug, and the oil gets displaced, you get metal-metal contact, and it sticks hard. Fast, and under compression, and the oil stays in the interface, no problem.
Same with ringed engines, except that they replace the low pressure an lots of surface area with high pressure and small surface area, the high pressure being the combuston pressure (maybe 400-500 psi) behind the ring forcing it out into contact. Tension-type rings count on some preload to make it work at low RPM during starting, Dykes rings have no tension, and count on the pressure "bell-mouthing" the asymmetrical cross-section so that only the upper edge supposedly contacts, riding on the corner. Whether and how long this actually works in model engines is highly debatable - most of the good-running Dykes ring stunt engines seem to have equal wear across the entire face of the ring, rather than just the top edge. I always figured they were far too thick in cross-section to actually "bell-mouth" in practice, at least for long.
Slight metal-metal contact, or debris, is what causes wear. Lots of metal-metal contact = seized. Ceramic helps because the slight contact is no longer metal-metal, and cannot spall off material from on surface to another, which typically causes more contact, more material transferred, then it stops abruptly.
This is just another type of bearing surface. Bearing tribology (the study the friction and wear in bearings) is a very complex and arcane subject, and appears to involve black cats and guys in conical hats emblazoned with signs of the Zodiac. All of these different experts tend to disagree on every topic, so, like all legitimate scientific pursuits, you choose which wizard to believe.
An interesting bit of information for our electric motor pals - it's possible to have wear from micro-arcing across ball bearing surfaces with as little as 3 volts differential between the balls and the races, so better figure out a way to ground the rotor to the stator...
Brett