65Ac Low Static RPM - Reasons??, Valves, valve springs??

[skookum]

Here is what my A&P has to say, does it sound reasonable or is there some other problems at hand? Does any one have any suggestions?


Hi Skookum,

Often I have found troubleshooting with older aircraft and engines a "problem" not be one specific problem, but rather multiple faults, which may create the illusion of a single problem and can be made better or sometimes worse by correcting one fault.

In this case, your aircraft had not made full power as proven by it not making full static RPM. It was also noted that it intermittently missed on the right magneto and had an excessive RPM drop on this mag. The installation of the new slick mags resulted in the engine starting very well and running smooth, with good mag drops (50L/50R). During the initial run up it made static RPM of 2050, verified with strobe tach checker, which is correct with your w72ck42 prop. It was then observed after 15-30 seconds at max power to drift down to 1900RPM where it then stabilized.

We switched the carburetor (yours appears to be recently overhauled or worked on but there is no logbook entry??) for troubleshooting and tried again with the same results, your carburetor was then reinstalled.

Typically this behavior is possible weak or broken valve springs. At higher power (higher oil pressure) the hydraulic lifters may overpower the springs and cause clearance issues with the valves. The next step in this process will be to inspect all valve springs. Your compression on all cylinders is very good.

Your airplane overall is in reasonable condition, but typical to all of its type the first in depth annual can be a prolonged event. Ultimately this results in subsequent trouble free annuals and an aircraft that flys trouble free for years.

Any questions please ask,

Cody

[Mikek]

Here is what my A&P has to say, does it sound reasonable or is there some other problems at hand? Does any one have any suggestions?


Hi Skookum,


Your airplane overall is in reasonable condition, but typical to all of its type the first in depth annual can be a prolonged event. Ultimately this results in subsequent trouble free annuals and an aircraft that flys trouble free for years.

Any questions please ask,

Cody

Sounds like he has a plan and everything he said is true and the first new annual does cover alot so he can get to know you both. I hope the springs help.

alittle more history of the airplane & engine might help, is this plane new to you or haveyou had it for awhile?

[Paul Agaliotis]

Cody,
The valve springs would be the last thing I would worry about. Sounds like the carb heat is rattling on or you have some kind of obstruction in the fuel delivery system. Pull all of the screens and check for debris. Try running it with the fuel cap off to eliminate a vent issue. Unless you can see a broken spring I would look elsewhere.
The RPM is pretty close for the Sensenich prop, assuming this is an A65.
Paul