Posted for "colyncase on earthlink" <colyncase@earthlink.net>:

 I have no operating experience with my tsio-550 yet.
 However, my understanding from APS and other sources is that the valves on
TCM cylinders as shipped from the factory are not reliable due to either poor
fit of the guides or misalignment of the guides.   Therefore, I would consider
it mandatory to have your valve guides bored or honed and the seats lapped or
ground to fit.  In a different mail, Jim opines that the seat should be ground
to provide maximum contact area for cooling.    Makes sense but I have no data
on that particular mod.
 
Further, I'm not sure everyone gets their fuel flow setup high enough for max
power ROP operations (e.g. takeoff and initial climb)  If you don't do that
properly you will get higher pressures and higher cylinder temps.  Some that
run ROP don't run rich enough.
 
 I'm hoping if I get all that right I'll make it to TBO but one would think
that if it were possible, some tsio-550 operators would have succeeded by now.
 
 Colyn