Large valves have their problems, that is why ( I'm quite sure ), that Steve quit using them in his heads. I went thru 3 sets of heads with the valves sinking in the seats, before an expert VW mechanic told me that the reason was that the aftermarket heads were cast using plugs for the exhaust ports to make it easy to just pull the plugs out after casting, and then when you grind it for large valves, you take off too much meat from the head so there is not enough left to support the valve and dissipate the heat.
I got a set of genuine VW heads (made in Brazil or Mexico, can't remember which), with standard valves and the mechanic ported them properly, by hand. Never had that problem again. That and all the other things that were found wrong with the engine being corrected and $5000 solved all my VW problems. That is the major reason why I did not build my Corvair engine and why I have had no problems with it. You don't know what you don't know until it bites you. See N64KR at <http://krbuilder.org/> http://KRBuilder.org - Then click on the pics 2015 KR Gathering - McMinnville, OR. September 3 - 6 -- See U There. Peoples Choice at 2013 - KR Gathering in Mt. Vernon, Il - MVN Best KR at 2013 - KR Gathering in Mt. Vernon, Il - MVN Best Interior at 2013 - KR Gathering in Mt. Vernon, Il - MVN Best Paint at 2013 - KR Gathering in Mt. Vernon, Il - MVN Best Firwwall Forward at 2013 - KR Gathering in Mt. Vernon, Il - MVN Best Interior and Panel at 2008 - KR Gathering in Mt. Vernon, Il - MVN Daniel R. Heath - Lexington, SC
