I don't use them either, as my machine shop adviced against it for my
Spitfire with standard iron valve guides - apparantly they need more
lubrication than the bronze ones, and the seals do limit the lubrication.
But I'd like to use them next time I have the head rebuilt. My inlet
valves were totally covered in very rough deposits, so bad that it clearly
ruined the flow (I'd run the engine for 1 1/2 season).
Besides this obvious problem I've read somewhere says that the oil that
gets sucked down contaminates the fuel/air mix and lowers the octane
rating of the fuel.
1963 Spitfire 4
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