Any cause for this other a sticky exhaust valve?

[RobertE]

Upon startup about half the time my IO360A3B6 runs rough for 3-6 seconds.  The engine was just overhauled 80 hours ago, I run LOP, lean on the ground and have CHTs in the 330-360 range.  My engine analyzer shows that the #1cylinder egt is about 150 within a couple of seconds whereas the others are about 300 and then catches up in about 20 seconds as all the temps rise.

80 hours and lean, low temp operations aren’t what I would expect to produce a sticky valve but, then again, I can’t think of another cause.  Anyone got any ideas?  Thanks.

[N201MKTurbo]

It could take that long for the fuel to get to the cylinders.

[Guest]

Classic morning sickness.

Clarence

[KSMooniac]

Time to ream that valve...I had to do a couple after 200 hours SMOH and that fixed it.

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[Yetti]

[HRM]

43 minutes ago, Yetti said:

 

That's disturbing. The opposite of 'plane porn'.

[thinwing]

Snake oil AKA Marvel Mystery OIL or engine builder guarantee 

[kortopates]

8 hours ago, RobertE said:

low temp operations aren’t what I would expect to produce a sticky valve ...

low temp ops is exactly what causes it to appear. 

[Yetti]

8 hours ago, HRM said:

That's disturbing. The opposite of 'plane porn'.

What was disturbing is the A&P having to take a punch and hammer to pound out the valve.  

[PTK]

7 hours ago, kortopates said:

low temp ops is exactly what causes it to appear. 

Paul, the op states he runs lop and CHT’s in the 330-360 range. Is that considered low temp ops? It has been my impression that temps in that range are considered good. No?

[kortopates]

Paul, the op states he runs lop and CHT’s in the 330-360 range. Is that considered low temp ops? It has been my impression that temps in that range are considered good. No?

Peter, you are correct that is not the issue. I was referring to his low temp comment thinking he meant low temp at start up when the sticky valve presented itself.

 

 

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[takair]

15 hours ago, M20Doc said:

Classic morning sickness.

Clarence

Clarence

Do you ever run into the he case where a lifter bleeds down fast or takes a while to pressurize due to dirt in them?  As I recall, this can cause similar behavior on start. I seem to recall cleaning lifters many years ago on a customer aircraft due to rough starts.

[Bob - S50]

Since the engine only has 80 hours on an overhaul, I would doubt that it is morning sickness so soon.

Bad plug?  Running on the good one until it warms up enough to clear the other one?

Bad wire?

Plugged injector?  Affecting the fuel air mixture?

Leaking line between the spider and the cylinder?  Making it take longer for fuel to get to that cylinder?

Cylinder flooding during start so it takes a few seconds to burn out the excess fuel?

[HRM]

4 hours ago, Yetti said:

What was disturbing is the A&P having to take a punch and hammer to pound out the valve.  

Yeesh! That would be worse than watching a Hostel or Saw movie!

[PTK]

3 hours ago, kortopates said:

Peter, you are correct that is not the issue. I was referring to his low temp comment thinking he meant low temp at start up when the sticky valve presented itself.

 

 

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Thank you Paul.

I understand that sticking can occur in a cold started engine when the valve guide to stem clearance is restricted due to coked oil. But I have another question: are there more than one type of valve guide that can be utilized in terms the material of which it’s manufactured? I remember reading somewhere that there is more than one kind of valve guide in terms of material and the OH facility can provide info as to which type they utilized. Is this true? And if so is one type more prone to sticking than another? It just seems odd that at 80 SMOH it sticks valves.

[RobertE]

problem solved.  I figure I ought to share the answer in case someone has a similar set of symptoms.

 Bob-S50 hit the nail on the head.  A way too rich mixture that caused a cylinder to miss for a few seconds.  It just didn’t seem likely that 80 hours of running the engine in a manner that is supposed to diminish the probability of a stuck valve would, in fact, produce a stuck valve.  The tell?  The rough running wouldn’t clear up in a instant (a valve that goes from not working to working produces smoothness abruptly not gradually as I was experiencing).  The mixture at idle was so rich that leaning it produced a 250 rpm increase, not the more normal 50 or so. There were also some other indications of a too rich mixture that I won’t go into. 

Anyway, before pulling rocker covers, up springing valves and so on I’m glad my A&P exhausted other possibilities first.

 

[carusoam]

Great follow-up, RobertE!

Thanks for sharing.

Best regards,

-a-

[kortopates]

Thank you Paul.
I understand that sticking can occur in a cold started engine when the valve guide to stem clearance is restricted due to coked oil. But I have another question: are there more than one type of valve guide that can be utilized in terms the material of which it’s manufactured? I remember reading somewhere that there is more than one kind of valve guide in terms of material and the OH facility can provide info as to which type they utilized. Is this true? And if so is one type more prone to sticking than another? It just seems odd that at 80 SMOH it sticks valves.

Peter, metallurgy of valve components is not something I am qualified to offer opinions on. I known the two manufacturers use different metals and designs; especially with regard to the lifters. But I am unaware of any choice we have in engine rebuilding. As far as I know that is fixed. But Lycoming do have a greater propensity for valve sticking over Continentals.
Happy Memorial day!



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