"On my current annual, two cylinders on my TSIO 550B2B show a small crack
emanating out from spark plug holes. Engine has 1200 hrs, cylinders have
570 hrs. The cylinders were fine in all other respects(good compression,
etc.). Anybody else had this problem?"

Carl -

YES I had what is probably the same problem back in late1997 - early 1998 on
the TWO engines in my Baron with IO-550-C engines. I first found 3 cracked
cylinders (two on one engine and one on the other) at about 807 hrs. I
replaced them and told my TCM rep I was concerned because I had NEVER had a
cracked cylinder in 10K+ hrs of flying various piston aircraft AND both
engines were consecutively serial numbered.

I replaced the three bad cylinders only to find MORE of them at 880 hrs. It
was a struggle but I got TCM to replace ALL of the cylinders on both engines
(except the ones I had previously replaced). The biggest part of the
nightmare was that at this same time TCM was having problems with some of
their valves being improperly hardened and ALL the cylinders in the country
were recalled for inspection so replacement cylinders were nearly impossible
to get.

When I had the first problem they just sent out three cylinders. The second
time around I sent a sample cylinder to TCM in Mobile for them for analysis.
The told me they sectioned it (cut it in slices) to see where the cracking
started and finished. They admitted it was their defect.

Background ......... TCM then (if not now) got their raw cylinder head
castings from two different vendors Eck and Oberdorfer. I can't remember now
but the ones I had were made during a period when the company that made them
was being bought out by a huge casting company (Citation Casting as I
recall). I suspect that somehow during the buy out quality control or the
process of casting the heads was affected.

The cracks I had all started at the edge of the top spark plug hole (just a
faint black line) and ran around the cylinder. On several of the cylinders
the crack was also visible by looking up into the exhaust port of the
cylinder.

You can see who the cast the heads by removing the rocker covers and
checking the casting markings.

You have my sympathies. NO FUN.

Ted Stanley - A&P-IA