I now have ~250 hours on an Aerovee in my Sonex. I've found leaky exhaust valves three times during that time. I re-lapped the offending seats a couple times, but I'm starting to think the correct remedy is to use something like a Neway cutter to re-cut the valve seat and replace the valve. I've read the Sonex forum for several years and recently read just about everything on the Sonerai forum. This seems to be a common maintenance item on all VW conversions. I didn't see anyone claiming to have hundreds of hours with no exhaust valve issues. I'm pretty sure these heads are from CB Performance and are also used by many of the other VW conversion companies. My first thought is that perhaps the valves don't come lapped into the seats well. When I buy my next set of heads, I'll definitely check this. I've also considered that the deposits left in the head from 100LL are abrasive to the valves faces and have begun using Decalin Runup to prevent the deposits from forming. I've found others who have done the same, but nothing conclusive. I'm doubtful it will fix this problem. I'm also curious about valve rotation. The Aerovee instructions have us assemble the rockers slightly off-center on the valve stems to impart a small torque to help spin them around. I monitor the wear on my valve stems and am almost certain no valve in my engine has rotated a noticeable amount in those 250 hours. I'm starting to believe that a lot of what I believe to be premature valve wear would be solved if the valves were actually able to rotate. I've talked to other builders and read other aircooled VW forums and I get the impression that the lack of rotation is extremely common. I'm aware that some engines use rotator caps to rotate the valves. I haven't found anyone who has tried them on aircooled VWs. I did find some people who claimed the original stock valve keepers (at the valve stem) didn't have a gap between them when installed fully so didn't grip the valve stem as tightly and allowed the valve to rotate, but others say that running with loose valve keepers pounds on the valve stem and creates its own problems. Is anyone flying a VW with valves that rotate? Any thoughts on a rotator cap that would fit the VW? I'm leaning towards buying a second set of heads and just swapping them out whenever I notice low compression, but part of me things something simple like valve rotation might be the answer.