Valve seat angles?
I'd thought that the standard valve seat angles were 30-45-60 but looking at a Subaru workshop manual it appears that the top-cut is 15 degrees, not 30 and there are more than three discrete angles there i.e. two different throat cuts?
My STi3/4 heads are off to have the seats and valves cut to spec, but should I ask for them to be kept at 15-45 for the top cut and contact angles, or get it recut to 30-45-60 if possible? Is there any advantage in one way or the other? |
I've never bothered with that. I've always just reground the valves into current seats.
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Well I think they've done the cutting now, so we'll soon see, when I go to collect them. Next problem is equalising the chamber volumes and getting the skim depth right, but that's for another thread!
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Is the technique of hairline valve seats still used on inlet valves? (higher seating pressure for a given spring force)
JohnD |
Well the contact widths are 1mm inlet and 1.5mm exhaust so no, not hairline. I suppose they go as narrow as they can whilst still being able to shed valve heat effectively.
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