Hi All.
What is the best valve seating width to use,{heat transfer] iam using new valves and the valve head is 1.2mm proud of cylinder face after I have cut seat.
The new valves have over size stems I brought from Modak, Aust, and I do not have to replace valve guides.
The motor I am building up is a 720cc.
Cheers with beers
Drew

email (option): bronte.nolan@bigpond.com

Hi Drew...The valve will sit above the level of the gasket face due to the 'land' above the valve seat face...That is there to prevent the 'lip' of the valve getting too hot (reduction of this below safe limits due to valve refacing is a common cause of valve failure..

Regarding seat width make the inlet one as narrow as you can...this helps gas flow at low valve openings...The seat itself is never exposed to a hot charge so has a much easier life...

Conversely, the exhaust valve seat should be as wide as you can make it...An 1/8" for example would be ok...A large percentage of the heat from the valve (which runs red by the way) is transferred via the valve seat so the more surface area the better. Gas flow is not so important here as the exhaust gas is being 'pumped' out...Ian

email (option): ian@wright52.plus.com

Thanks again Ian.
Cheers Drew

email (option): bronte.nolan@bigpond.com