Valve Coatings

[mark allison]

Guy
Piston coatings have been around for awhile now and are proven. I'm now starting to see advertisements for valve coatings. Have you experimented with any coatings?

[Guy Croft]

I don't believe in most coatings though as the man responsible for tribology at Napier I learned more about them than most. That goes for chamber and port coatings, piston and cylinder coatings, valve, exhaust coatings of all kinds. The exceptions are ring and piston pin. My only coating I have time for is oil.

Since you kindly asked, coatings on valves - especially the very hard plasma coatings now popular - are a real nuisance when it comes to altering valve size or shape by grinding and at overhaul because they knock the grinding wheel to bits.

I'm sorry if that is a rather dull and contemporary view but if anyone wishes to add their thoughts please do so,

G

[mark allison]

thanks for the response. I assumed they were only coating the valve head. You don't feel coating the sides of the pistons is worthwhile?

[Guy Croft]

I think a lot of the impetus came from Formula 1. If you're coating have regard for the fact that engines like that are stripped after every race (or at least, when tribology was first taken really seriously - used to be) and with such a short lifespan the coatings are going to last OK. How long they will in other applications is another matter.


G