Continental C-145 Prop very tight on shutdown.?!

[Bruce Fenstermacher]

DEM, a stuck valve won't seize the engine. The valve train from the cam to the valve has much more force to move the valve open than the valve spring has to return it closed. As the valve gets tight in the guide it will stop in the open position against the spring. The valve train lash will be loose and no damage usually takes place.

I have had a stuck valve while in flight with the engine running. This being on a A-65 which has essentially the same hydraulic lifter, pushrod, rocker arm, valve and valve guide. I had reduced throttle and shock cooled the cylinder. On throttle advance the engine was running on 3 cylinders. The valve was stuck open. And it was really stuck requiring heat and brass ball pean hammer to drive it out of the valve guide.

I've never seen nor heard of a valve stuck closed on an engine in recent serviceable condition. Most stuck valves that actually stick in one spot are found open upon start up after seizing when the engine cooled after the last run.

So the engine will rotate either way the same with a stuck valve.

Stuck ring you won't hear or feel and likely low compression will be the result. Broken ring gouging into the cylinder will most certainly cause low compression and metal in the filter and screen.

[GAHorn]

A valve stuck CLOSED....will bend the pushrod and cannot be fixed by any simple "rope trick". It requires real wrenches, disassembly, and beer.

[mnlanese]

OK Folks,

Thanks for all the replies. It looks like we found the problem. The good news is that the bottom end is good. The bad news is at least 2 cylinders are bad.

Ive been noticing a higher then normal oil consumption over the last year or so and it appears that there is excessive play in the ring groove area, a few rings stuck with carbon and lots of blow by. Not sure how it developed. I can't seem to find any record of piston replacement in the last overhaul (before I bought it). Maybe they were trying to save money on pistons or maybe they were bad parts but the result is burning a lot of oil and sticking rings.

As of today the plan is to pull them all and send them to our local expert machine shop for evaluation. At the very least they will be cleaned, inspected, honed and new rings and pistons installed. If there beyond that then I'll probably do new cylinders.

I was wondering what to do with that extra money.....

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[johneeb]

Matt, be careful turning the crankshaft without first putting some tension on the through bolts. You do not want to risk shifting a main bearing.

[cessna170bdriver]

Matt, be careful turning the crankshaft without first putting some tension on the through bolts. You do not want to risk shifting a main bearing.

Good point John. Also, on reassembly, you want to make SURE check torque on every throughbolt on BOTH sides. Failing to do so can result in case fretting, spun bearings, and/or cylinder(s) coming loose from the engine. None of those things end well or inexpensively.

Oh, and not intending to start an argument, I quit having stuck valves and rings due to carbon when I put my engine on a steady diet of 100LL. Just a simple fact...

[GAHorn]

Matt, be careful turning the crankshaft without first putting some tension on the through bolts. You do not want to risk shifting a main bearing.

Good point John. Also, on reassembly, you want to make SURE check torque on every throughbolt on BOTH sides. Failing to do so can result in case fretting, spun bearings, and/or cylinder(s) coming loose from the engine. None of those things end well or inexpensively.

Oh, and not intending to start an argument, I quit having stuck valves and rings due to carbon when I put my engine on a steady diet of 100LL. Just a simple fact...

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[hilltop170]

Did you discover where the squeaking sounds came from? Maybe a piston pin rubbing on the cylinder wall?

[mnlanese]

It might have been the pin cap on cylinder wall. In the photo you can see clear marks from the pin caps. Not sure if soft metal would make a squeaking noise. We did find a stuck ring and I'm leaning toward that as a cause.

ML

[hilltop170]

I agree with George, piston pins are money well spent. Also, check your oil screen and filter if you have one and if you see aluminum debris that looks like fingernail clippings, that came from the piston pin caps.

[dunlaps3]

I have seen this problem 2 times in the past. Exactly as you describe. Both times it was the piston pin plugs rubbing tightly on the cylinder wall. Why a pressed-in pin pushes out and drags that hard still puzzles me , but it does happen. On one cylinder it wore a groove about .006 deep. Aluminum wearing down steel , go figure. Andrew

[MoonlightVFR]

I am curious about the two (2) cylinders removed.

What was the compression on those two as related to the other 4 cylinders?

Did the piston ring Lands show damage?

[mnlanese]

I'll have to look in the books for the specific numbers but at last annual all the compressions were high 70's I think the tell was the high oil consumption.