O470 stuck valve

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Mtns2Skies

Final Approach
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Mtns2Skies
After putting 1000 hours on my 1989 FRMN engine continental O470, ive finally had my first engine related issue. Not that they're necessarily related, but about 6 hours ago I put a powerflow exhaust on the plane which has made a big difference in power.

I go to start up to help get the 170 to maintenance and cylinder #6 is missing pretty badly. I add power and get some heat into the cylinder and get it to about 200CHT with no improvement, and below 1000 rpm it doesnt fire at all.

I taxied back to the hangar and shut down. Pulled the prop through and yep its missing compression on #6.

Ive never experienced a stuck valve before. Is my a&p doing the rope trick and reaming the guide a true fix or is that a bandaid? Was I operating the engine incorrectly for this to happen? Educate me please.

It is a high time engine in age, and im approaching TBO on hours. Is this a symptom of the engine needing an overhaul? Or a new cylinder? Or is this generally an isolated independent problem?
 
Mtns2Skies said:
Or is this generally an isolated independent problem?
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All things considered this would be my 1st guess. But I suspect once your mechanic looks at it you'll probably have cylinder removal in the near future for a more permanent fix. If you have access to one, perhaps take a look yourself with a borescope to see whats up?
 
Borescope first to make sure the valve isn't burned up.
 
I only say this because you mentioned the Powerflow. In an almost completely unrelated world - karting and the KT100 air cooled aluminum cylinder 2 stroke - if we tighten the exhaust header too much we distort the cylinder.
 
You may want to listen for a “ clanging” noise while turning by hand

and observe safety. I met a O-470 where the Exhaust Valve would stick

open until the Piston touches it. IMHO that doesn’t help.
 
Uhh so a&p looked and everything is working great. No issues. Self healing cylinder?

Maybe a carbon deposit on the valve seat?
 
I've run plenty on the E-225 which is early version of the O-470. The expert I first learned with told me to run it lean on the ground as much as possible. When the engine isn't fully warm, and it's also full rich, seemed to be the time that I had sticky valve syndrome. As soon as the engine runs smooth after start, I lean aggressively until runup and take off. So far, I've only had to rope-trick one time and that took care of it.
 
Barrett50 said:
I've run plenty on the E-225 which is early version of the O-470. The expert I first learned with told me to run it lean on the ground as much as possible. When the engine isn't fully warm, and it's also full rich, seemed to be the time that I had sticky valve syndrome. As soon as the engine runs smooth after start, I lean aggressively until runup and take off. So far, I've only had to rope-trick one time and that took care of it.
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I lean very aggressively on the ground. So much so, that if I advance the throttle the engine stumbles. This prevents attempted too-lean takeoffs.
 
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Sticking valves don't heal themselves. It's giving you notice.

I watched a couple of owners deal with sticking valves using home brewed remedies only to end up broke down somewhere away from home needing a cylinder pulled and the other ended up with a bent push rod and a broke tappet body.

Here recently I watched a goober with his clapped out Navion trying to do full power runs outside the hangar to "free up" a stuck valve. Darwin strikes again.
 
To add to the doc’s anecdotes, you can find success or failure in every aviation scenario if you look for it. If your mechanic says to send it, go fly. If it’s a problem, that sticky valve will let you know inn the next few starts. Now you know to be extra attentive to it. Be careful out there, fly on!
 
The rope trick is for fixing leaking valves (cleaning up the seat), not stuck valves which would indicate a problem with the stem or guide.
 
455 Bravo Uniform said:
I only say this because you mentioned the Powerflow. In an almost completely unrelated world - karting and the KT100 air cooled aluminum cylinder 2 stroke - if we tighten the exhaust header too much we distort the cylinder.
Click to expand...
KT 100, direct drive, Tonykart. What a hoot! You bring back fond memories.
 
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