Misfire or ??

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Dana

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I do not intend to pull the head off, unless simply retorquing it doesn't solve it. Only 30 hours or so since the heads were off for the valve job, so yes, they probably should have been retorqued at least once before now. I don't recall the stud size or torque value offhand, but it's in the Mosler (not Global) manual.

Dana
 

delta

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May 26, 2011
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Brookside Utah
There was a great article written a few months back by Mike Bush in eaa's sport aviation about proper torque values and how to obtain them. I'll look up the issue if you want. The gist is, if the threads are clean and dry the torque value will be reached before the intended pre-load is. I personally use loctite on oil free nuts and studs as the lubrication. You probably have case inserts where the studs go and a over torque test is probably not necessary. I wouldn't go over the stated torque value by more than 4 or 5 lbs for a test if you feel it necessary, and for sure re-torque afterwards to specs.
If your CHT and EGT's are staying in the green the loctite should help keep the ones in the oil bath from backing off.
 

StarJar

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Sep 6, 2011
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El Centro, California, USA
OK just one last comment because I didn't include ALL factors.
You have to realize that on a car, it's a major hassle removing a head, IIRC it involves removing lots of stuff in almost impossible to reach places, and so if retorquing the head works, you're ahead of the game.
In your case its much easier, since because once you have the rocker shaft off, all that's left is the intake. Well, there is also the issue of pushrod tube end seals and stretching the tubes back out (if you have the stock tubes, but as I recall you have aftermarket tubes).
Non removal won't lead to anything catastrophic, so its just a matter of choice.
It is possible that hard particles are in the leak gap, but I don't have enough experience with that to say the if the odds are 2 to 1 or 100 to 1.
 

Dana

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I flew today after retorquing the heads. (I would have flown two days ago but my left brake failed as I was taxiing out so I had to fix it, always something...) It appears as though it was indeed a loose head, as at least one of the nuts was definitely looser than the specified torque, and the engine is no longer making funny noises. The loose nut was the one with the CHT sender (a copper eye terminal) under it. I loosened them all, wiggled the head a bit, and torqued them back up in several increments. This time, I paint marked the nuts to monitor for looseness and I'll check / retorque them after a few hours of operation.

I'm glad it wasn't ignition. That would just have pissed me off, with all the work I'd done on that front (stay tuned for my article on magnetos for half VW engines in the July Kitplanes).

Dana
 
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