: 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...

Your "broken ring" theory sounds likely. There are a few issues that may crop
up and modify the decision. What I would do is the following:

- Borescope all the other jugs and verify only one is burning lots of oil.
- Look *carefully* around the exhaust bosses and spark plug holes of all of the jugs.
- Pull off the oil filter/screen and take a look inside. See what you find, and how
much of it is aluminum/steel, etc.
- Rig up a jig for a dial indicator on the valve pushrods

If it's a 1500 hour engine, the bottom end should be in good shape still...
unless the cam's eaten itself (thus the dial indicator). If there's nothing in the
oil filter, even better indication that nothing bad is going on on the bottom end.
There may be some gunk for the jug that blew the ring.

What may have caused the ring to die? Low octane or lean mixture?

There's nothing inherently wrong with a jug going bad after awhile...
particularly heat-related cracks. That's no real reason to go down the slippery slope
of:
"If I overhaul/exhange one jug, should I do them all for a TOH?"
"If I'm going to overhaul, maybe I should buy new?"
"If I'm going to do a top overhaul, maybe I should split the cases and do the whole
thing?"

Pull off the bad jug, take a looksee (including the cam lobes you can see from
pulling off one jug). If it's just a blown ring and there's nothing visibly wrong
with the jug, put a set of rings on it, hone it, and throw it back together. You may
have to replace the piston.

In any event, I wouldn't let a cracked ring push you to an overhaul if
everything else is in good shape. Removing all four jugs is *almost* 4x the work of
removing just one. Splitting the case and doing the bottom is a LOT more work and
expense.

-Cory


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************************************************** ***********************
* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
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