text news wrote:
snip
: One big question......
: As far as we know, there is nothing fundamentally wrong with our engine and
: it has a "known" history, no prop strikes or anything nasty. What is the
: chance of finding a cracked crankshaft or something equally nasty?
: If we have our own engine overhauled (zero timed) is that better than
: swapping it for a Lycoming overhauled engine whose history we have no
: knowledge of?

The engine in my airplane (O-360-A4A) has been overhauled 3 times, and now
has 6200 hours total on it, 900 since it was overhauled last. It still
has the original crankshaft, crankcase halves, etc., but the cylinders,
camshaft, pistons, etc. have been replaced. If your engine is running well,
and you know its history (as it sounds like you do), there is no reason
not to have it zero-timed. Do investigate what components will be replaced
with new, such as the camshaft which is a known weakness in Lycoming
engines. In general, the more components replaced with new the better.

On an opposite note, some years ago a friend of mine purchased a Warrior
with a worn-out engine. Since he did no know the history of this engine,
he opted for a Lycoming zero-timed engine. Recently he had a serious problem
with this engine. After 6 years and 600 hours, the case developed a crack.
Lycoming took the engine back (out of warranty!), replaced the cracked
case half and all of the wear items inside (bearings, mainly), and returned
the engine. My friend was charged only for shipping. I would doubt that
any other shop would do the same.

: I have heard that engines can only be re-worked about three times before
: they are out of spec. If we get a Lycoming exchange engine how do we know
: that it hasn't already been re-worked two or three times and would be
: rejected at the next overhaul?
You do not know the history of any parts in the exchange engine, unless they
were installed new.

: It is a serious amount of money to find and I just don't have the knowledge
: and experience to know what is the best route to take. Instinctively I
: rather like the idea of having my own engine overhauled and keeping the
: original plane intact, but maybe I am too sentimental!

You might consider a "custom overhaul" by Lycoming, wherein you ship them
your engine, they overhaul it, and ship it back to you. The downside is
that the time required would be longer than exchanging the engine, as you'd
need to ship it to the US, and have it shipped back to the UK.

There are a few websites you might look at:
www.textron.lycoming.com has some information about the terminology used;
www.mattituck.com is a major US-based overhauler of engines;
www.pennyanaero.com is another US-based engine overhauler.

--
Aaron Coolidge (N9376J)