On Sun, 2 Oct 2005 23:21:21 -0400, "John Doe"
wrote:

below

Can someone tell me their experience with the engine maintenace in relation
to having to top overhaul the cylinders? I've heard from some owners that
you should only expect about 800 or so hours on the cyliners before having
to get them topped, while others have said if flown properly they should
make it to the engine TBO.

Are the cylinders 800 hours since new nitrides? oversized steels?
chrome? Factory o-haul? name-brand "new limits" o-haul? field o-haul?

Is it intercooled? What power setting used for cruise? Average cruise
altitude? Oil temp at cruise? CHT at cruise? TIT/fuel flow at cruise?
Oil consumption per hour? Calender time since OH? How long did it
typically "sit" without flying? Pretty sure I've mentioned this
before-how many total hours on the exhaust components SINCE NEW?

If the engine in question is not intercooled, has been operated at 75%
@peak TIT (or 50 degrees ROP) regardless of oil temp/CHT, flown
infrequently, it's entirely possible that the e-valve guides are
going/gone and the cam is well on it's way.

If the engine in question is intercooled, has spent most of it's life
with the oil temp at or below 200 degrees F, CHT at or below 400
degrees F, it's still entirely possible that the e-valve guides are
going.

The plane I'm looking to buy has 800 hours SMOH and they haven't touched the
cylinders since the overhaul. Am I looking at a heavty bill to top the
cylinders soon? (I'm thinking about getting a prebuy done this week) Will a
compression check tell me what I need or does the A&P have to tear the
engine apart to really tell?

If the engine isn't making metal, and periodic oil analysis looks
good, and the compression is good (no e-valve leaks) there is no
reason "to tear the engine apart". Don't know too many people selling
'planes that are going to let you "tear the engine apart" as part of a
pre-buy.

E-valve leaks on a Lycoming typically means the guides/valves are
trashed. At 800-1000 hours most big-six Lycoming E-valve guides are
marginal. Have personally had them go to TBO without this being an
issue (e-valves don't leak). Have also had them develop e-valve
leakage, requiring repair.

Again, not sure exactly what you are looking for. I've allegedly
maintained a crapload of turbocharged Lycomings for tens of thousands
of hours of operation, but my crystal ball's busted. Have seen S1AD's
go 1400-1600 hours without "cylinder" issues, have seen them with 400
hours that needed the cylinders thrown in a dumpster. It depends on
both the actual overhaul and the shivering mass of tissue between the
seat back and the yoke...

TC