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Eddie's Grumman engine failure - more info please


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From another thread:

Once I flew my Grumman Tiger with my family from from S FL to CT for XMAS with relatives. On startup to fly home, the engine seemed a bit rough initially. I chalked it up to the plane not being used to cold weather, and it had smoothed out by the time I did the runup.

Then, about 10 minutes after takeoff all hell broke loose -RPM loss, backfiring, vibration, you name it. This at about 6,000' over Long Island Sound. I declared an emergency and headed to the nearest airport. I had enough power to arrive over it with sufficient altitude and circled down with partial power for an uneventful landing. Upon deplaning, there was oil covering the nosewheel fairing, and I found this under the cowling:


Eddie, you've left us half in the dark here.  There was no photo of what you found under the cowl, and I don't get your explanation of the failure.


A valve would need significant amounts of moisture to be present to freeze in place, which you wouldn't expect to find in an engine after a long flight.

The pushrod can only have been bent at the moment of startup. 

Did you ever figure out how this made the engine

A. first run a little rough,

B. then run properly at full power, and 

C. then suffer massive sudden failure with power loss, backfiring, vibration, etc.







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I'm not Eddie, but Lycoming engines have a problem with what they call morning sickness. This is a case of the valves slightly sticking. Not enough to cause damage, but enough to make you say huh. On rare occasions like Eddies the valve stem will finally stick hard causing the valve to stay in the open position. When this happens the pushrod will bend causing the pushrod housing to lose its seal. This will cause a oil leak.

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I see - Frozen Valve describes the problem, and has nothing to do with Christmas time in the north!  


So was this a case of Morning Sickness delivering a baby - the valves suffered a common hiccup on start up (and Eddie said 'huh') but after ten minutes the problem came home to roost with a fully stuck open valve - ?


If that's the case then, Eddie, you wouldn't have gained anything by abandoning your fight to investigate.....

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