Engine Compression Question

[hilltop170]

To add to your list,

-how many years has it been since overhaul
-how has the plane been stored (hangar/outside)
-where has the plane been based (desert/hot humid coastal area)

All these contribute to what condition the plane will be in.

[GAHorn]

Low compressions alone are not much to go on when evaluating an engine which has been sitting a long time and which was last overhauled/repaired decades ago.
My IO-470s in my Baron were last overhauled in the early 1970s, run thru mid-life, then sat for four years outside in New Smyrna Beach Florida. The cylinders showed rust above the pistons with a boroscope.
The TCM factory field rep advised me to keep flying them.
That was 1995.
I flew them five years and then sold the plane which is still flying with those engines which are now way-past recommended TBO.... and doubtless still rusty inside.

I agree with Tom. Change the oil, run/fly it and change the oil again soon. That second oil change will tell the story. (Meantime, argue the price so as to cover early engine replacement/rebuild.)

[T. C. Downey]

I flew them five years and then sold the plane which is still flying with those engines which are now way-past recommended TBO.... and doubtless still rusty inside.

Nope, I doubt it, When you first started the engines the rings scrapped the rust off the cylinder walls, and dispersed it thru out the engine some goes to the oil side, the rest simply gets blown out the exhaust. This action leaves pits in the cylinder walls, these fill with oil, when the piston is higher in the bore and the excess oil is scrapped off as the rings go past them on the way down, the oil left in the pit gets burned leaving hard carbon in the pit. after a few hours the pit will fill and get polished smooth, and the oil consumption stabilizes and the engine is happy again.

[GAHorn]

100 hours later the rust was still visible at the top of the cylinders where the top ring travel limit was reached. No pitting was observed in the bright and shiney bores.

[blueldr]

When you're looking to buy a Cessna 170, I strongly suggest you make every effort to fly each one of the three types: the C-170, the C-170A, and the C-170B. There is a pronounced difference in them. Be sure you get the kind you want to keep.

[GAHorn]

Yeah, but it looks like the previous overhaul went 2800 plus hours? (and over 18 years) while the most recent doesn't mention if the overhaul included new cylinders...or simply "repaired" the 2800-hr cyls....and then did a "top" ten years later. ???

[170C]

Its interesting to see what some of the items cost back in the 1980's. When I did my O-300 overhaul in July of 1999 the cost was just over $13k. This included 6 new ECI steel cylinders with new pistons, a replacement accessory case, etc. While it all seemed expensive, the one single item that really got my attention was the cost of the main oil pump gear. As I recall it ran approximately $750 with my mechanics' discount My old one was worn beyond limits and is now painted Continental Gold & sits on a shelf in my office. I had a friend who had his Continental IO-360K overhauled prior to my overhaul and he too had to replace what he said was the same gear. However, if what he told me was correct, that same gear was used in a Diesel engine (maybe Cummings?) and he provided it to the overhaul shop (obviously without proper paperwork) to be installed in his engine. His cost on that gear was less than $100 and to the best of my knowledge that engine is still being operated with that gear although with a third owner. An interesting story if indeed true

[GAHorn]

Frank, that'd be a really-interesting post if you had included the Cummings part no.

[blueldr]

George and Frank,

Please be advised that the world famous diesel engines referred to are spelled "Cummins", for "Clessie L. Cummins", father of the highway diesel.

You will later be tested on this.

[GAHorn]

Hey, ... I only repeated what Frank claimed to be a mfr's name..... I didn't know what submarine he was stealing it from....