National Aeronca Association Bulletin Board

Hi All,
I own a Chief but for various reasons haven't flown it very much. And now that prime flying weather has finally arrived in the Pacific Northwest, and the airplane is finally in one piece, I'm perplexed by an engine issue -- it has a noisy idle; a sort of regular "clunk" that seems to be 1/2 crankshaft speed. The sound is quite noticeable at 800 RPM but I can't hear it above 1500 RPM. All else seems normal -- starts on first blade, static RPM is about 2100, oil pressure runs about 35-40 psi, cruise oil temp indicates about 140-150, left and right mag drop is equal at about 50 RPM, no metal in the screen. The sound is the same with the engine hot or cold and hasn't changed since the first time I ran it. The logbook lists time since overhaul at around 600 hrs. Is this sound characteristic of an A-65? If not, any thoughts about what causes it? Valve lifter that won't pump up; bad bearing; cracked bearing journal; too much MMO; not enough MMO? Here is a clip of the engine at idle and run-up. The ticking rattle that comes in at 0:40 isn't an engine noise, so try to ignore it: https://youtu.be/uDlJiWfsEic Help is appreciated,
Raleigh

Chief Pilot,

This sounds normal to me. My champ with the A65 and now the C85 sounds the same. my A65 had 180hrs ttso and the C85 has 50hrs ttso by Lycon. My chief with an A65 also sounds like this. Have an IA listen to it if you are still concerned. From what i can hear on the video though it sounds normal.

Raleigh,
Check to see that the prop isn't loose. If it's wood, as the weather changes they will dry out a little and will get loose. Sometimes you can smell wood burning if it gets bad.
Paul

duplicate

Thanks Paul and Bo. Quite difficult to diagnose engine problems by You-tube, but I appreciate the effort. I check torque on the prop bolts regularly, most recently earlier this month, so I know the prop isn't loose. I found this from Continental guru Harry Fenton: "I never really cared for the sound of short stacks. Because of the placement of the stacks, the fuselage can block the exhaust noise for one side and the engine kind of sounds like it is missing." Maybe that's what I'm hearing. Next time I run it I'll stand front and center and see if the sound is still there.
Thanks,
Raleigh