Continental C-90 question...

[cargoflyr69]

Got an update. i flew a bit of an x/c yesterday morning and lost about 1.5 qts in 2 hours (we went for a diagnostic 100hr hamburger) Before doing that i washed EVERYTHING on that airplane and when we got back we pulled the cowl and went over everything with a fine tooth comb. it does look like there is some fresh oil coming off the breather and burnt oil in the exhaust stream, on the belly and strut only on the #1 cylinder stack. we did another compression check and got 76 at TDC and 70ish and hissing at TBC. We cant tell where the air is going (valves, breather, oilpan, fill tube, ect. as was previously mentioned) its easy enough to pull the jug, so we did. the rings were all there and intact. There is a good engine shop in town that will be able to check all the jug/piston components for under 50 bucks and tell us what is up. Thats the route we are going to take for now, unless anyone has other ideas.


On a positive note I did get to fly yesterday and have green beer afterwards!

 

[avbug]

Cargolyer,

As Belchfire noted, still not sure what you're looking for with the piston at the bottom of the stroke. Compression tests, a differential pressure leakage test, is done with the piston TDC on the compression stroke. Where the air is going at the bottom of the stroke isn't particularly important...there's really only one place for it to go. Bear in mind that if you do have excess cylnder wear and you're getting a lot of blow by at the bottom, then You're also putting pressure to the valves from the back side via the guides. If you're hearing air leaking past them at this point, BDC on the power stroke, you have leaky guides. Maybe. Checking for play there, as well as valve stem stretch or warpage should be done while the jug is off with the springs pulled.

Was she smoking?

No sticking oil control ring?

Did you hunt around the jug itself, top and bottom and look for wetness between the cooling fins, or anything shiny (metal) near the barrel/cylinder head?