snip

However, my real problem with the valve assertion is that I really don't
know anyone who managed to run one of these little air cooled engines long
enough and hard enough to burn a valve. I do know of two broker cranks on
Corvair conversions (same person) and at least one, and possibly two, broken
cranks on VW conversions (same other person). Both are mentioned on the
FlyCorvair site, so I am really not adding much that is new. I am convinced
that all of the failures were torsional damping issues. The only burned
valve that I know of on an automotive conversion was on a liquid cooled
Geo/Suzuki engine and was traced to a carburetion problem--which was run at
a much higher power level. I was told that the carburetion problem was
corrected and has not recurred.

On the other hand, I strongly suspect that very high power levels equate to
accelerated wear; and I really dislike very short TBOs. So all of my own
scratch pad doodles are based on continuous power levels of less than 0.5
hp/cid, and usually significantly less.

Peter



I drove a harvesting machine that used hydrostatic drive and a VW engine
for power. We ran it on a governer at 3950rpm 24x7 all summer. Once I
was moving it from field to field and dropped a valve when I ratcheted
the motor up to 4100 because the machine travled at the speed of growing
grass. Of course this was after about 10 weeks of continous operation so
in terms of hours it was due.... The vale seats were pretty hammered as
I recall.

Lets see, 24*7*10=1680 hours.

Dave
PDX