Mike Busch has an article on Avweb where he discusses this topic. His
conclusion seems to be to repair/replace only the affected cylinder. If you
repair the cylinder for $500, it only has to last a short while to be more
cost effective than the other options. The conclusion seems to be based on
the assumption that the failure of one cylinder does not indicate that the
others are about to fail..

Mike
MU-2

"Denny" wrote in message
oups.com...
It turns out that the fouled plug I mentioned last week is oil
fouled... I suspect that the rings have gone... I will borescope the
cylinder for damage and check the seal on the intake valve stem, but I
suspect the worst... It is burning a quart every 1.5 hours, suddenly...

And the story gets complicated... The engine is roughly 1500 smoh...
The cylinders are old reruns... The case/crank is ~ 1958 manufacture
with nearly 6000 hours in the log book... It is unlikely that Lycoming
would take it for core credit... So the options are (in decreasing
cost):

Factory New (How much? I see, umm, let me get back to you on that.)

Factory rebuild - unlikely to get core credit, so total cost about $25k
+ labor

Field overhaul (my mechanic refuses to OH engines anymore so I will
have to ship)
~$9K base cost plus parts that won't make it - I'm guessing $15K +
If I remove the engine I will have the mount overhauled, new hoses,
etc...

TOH with 4 new Titan cylinders - ~$4K plus Shipping and Labor

1 new Titan cylinder - ~$1K plus S&L

Overhaul the cylinder - maybe $500 total...

Overhauling one cylinder gets you into RCR ( russian cylinder
roulette)...
Both the mechanic and I agree this is not the best route, but it is the
cheapest initially... He wants a factory reman to hang, of course...
The issue with changing out one cylinder is if one cylinder is gone at
1500 hours, how long before the next one, etc...

Doing a TOH at 1500 hours doesn't initially seem cost effective, but it
is where I am leaning... The bottoms on 320 150HP engines will, in my
experience, go lots longer than the 2000 hour recommended overhaul...
If I can get another 1000 hours out of the bottom (2500 total), which
is possible, both I and the airplane will likely be retired from flying
for other reasons...

decisions, decisions... daaayum...

denny