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Bob, You are absolutely correct,..... I use the skirt coating as another insurance policy,...the combustion chamber coatings I believe, are very functional in many respects,..not the least of which is heat rejection,...which helps the piston survive,..and leaves more heat in the gasses where it belongs and contributes to increased power. Remember I do a lot of work for the Harley air-cooled motors and improper warm-up and break-in seems to part of the life style,...no matter what you do, someone can ruin good work quickly ! The coatings are applied with a detail air-brush and heat cured. I think the non- OEM coatings are more sacrificial than permanent,....but they are relatively inexpensive,...and I honestly have not observed any component failures on any coated parts, mine or others ! Jeff Churchill J.C. Performance 617-06 Bicycle Path Port Jefferson Station NY 11776 USA tech: 516-928-6679 or 516-928-9863 website: http://www.jcperformance.com/ On Tue, 9 Nov 1999 09:46:42 -0500 <shammar@nsk-corp.com> writes: > > Are you using that Dow Corning Molykote on the skirts? How is it > applied? When > I worked with them on a development project in a previous life as a > piston > engineer, they were promoting a screen printing process. We found > that getting > the coating to stay there over the long haul was difficult, although > it has made > its way into some production programs. Gimmick or true benefit, I'm > not really > sure. Any opinion/data on this? > > In my opinion getting the ovality and profile of the skirt right are > more > important. Since the skirt/cylinder interface operates under > hydrodynamic > lubrication once the engine is running, frictional loss is a > function of the oil > viscosity (shearing forces) as long as there is no hard contact due > to a profile > problem. Therefore the only benefit of the skirt coating should be > on startup, > or if the shape of the skirt is marginal to begin with. > > I don't mean to bash your process- those are just my thoughts, based > on what my > Brazilian friends at Metal Leve taught me. > > Regards, > Bob > > >