Just a quick question. Took my head apart for machining work and now can't remember if the two part valve caps go on the inlet or exhaust valves. Haynes doesn't say and the diagram is unclear in my copy. Would be grateful if someone could confirm please.
'72 Sixfire 5 speed in Black- Daily driver '72 GT6 in Signal red-Pride and Joy
James, I think spinning the valve is meant to keep the valve seat, and the seating surface on the valve itself, cleaner. That way the valve stays gas tight longer and is less prone to burn in the case of an exhaust valve. The bad side of rotating the valves is that the arrangement that spins the valve is heavier than a plain valve retainer and thus requires more spring pressure to return the valve to its seat and keep it there. Or viewed differently, valve bounce will start at a lower RPM with the rotaters than without. Cheers, Paul
The two part caps spin the valve— can't remember the reasoning why— to keep it cool somehow?
Evens wear, and helps prevent localised hot spots (though the second point is less likely to be an issue on such small valves). Bigger engines actually have turbine blades fitted to force the valve to spin.
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