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Low compression on O-235-C2A


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Hi Cozybuilders and flyers,



My last "Leak test", (compression test) on my O-235-C2A powered COZY was not satisfactory. All 4 cylinders were below 70 (in the 60's) and 2 were even just below 50.

The engine has 2550 hrs TT and was "opened" by the previous owner and builder at 2100hrs TT. Some new parts have been installed (like new piston rings) at that time, but the cylinders are still the original low compression ones.


Oil consumption has been very good (1qt per 12 to 15hrs) and the Oil pressure is nice and high as well. I have not felt any difference in T/O and climb performance during the last flights and the engine runs smooth. I decided to ground the aircraft until further investigation.


The compression test has been properly carried out by a licensed and up to date, A&P with a hot engine. Previous compression tests were all in the 70's.

A friend of mine, that has an engine overhaul company (for cars and trucks only), will have a look at the cylinders early JAN '04...


My questions are the following:


What would you guys do....? New cylinders,...? Installing an O-320 is not an immediate option, since I really like the O-235 for it's low fuel burn (especially at 7$/USGAL in Europe).

If buying 4 new cylinders, where would you buy them? Straight from a Lycoming dealer, from Superior, or something else?

The O-235-C2A is a low compression engine, any idea if I can easily upgrade to high compression pistons? Any consequences?

All other tips are more than welcome.....


And last but not least, please don't let this post go into another useless discussion on auto conversion versus Lycoming engines.....




Best regards,


Cozylover Bjorn




Flying was my first love and it will be my last one!

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