Ask Paul: What causes this popping sound?

Q: I am test flying my new RV-9. It has a new Superior O-320, dual p-mags and an MTV11 2-blade MT prop. When it has been running at cruise power for a few minutes or more (say 2,300 rpm x 23 inches or more) and then I reduce the throttle, I get a popping/crackling sound from the engine. If I reduce the rmp before pulling the throttle, it doesn’t seem to do it so much. This typically happens when joining downwind to land, but other times too if I pull the throttle.

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Ask Paul: Why is my spark plug oil-fouled?

Q: I have been noticing an intermittent miss on the left mag during mag checks on the O-235L2C in my 1981 Cessna 152 (about 670 SMOH that included new Lycoming cylinders and pistons). About 30 hours ago when I cleaned, regapped, and rotated the plugs, I found that the lower plug on the #4 cylinder was filled with oil around the inner electrode and ceramic insulator. [Read more…]

Ask Paul: Tips to getting Dad’s Pacer flying again

Q: I was reading your explanation on the difference between narrow deck and wide deck Lycomings — what an excellent piece of writing. My interest is that my brother Lee and I have my Dad’s PA-20 and, while stored indoors, it hasn’t flown since 1964 or so, but I’m thinking (perhaps foolishly) about putting it back together. I’m thinking the old O-290-D-2 (while in excellent shape and only 200 TT, but 7/16ths valves) will have to go. An O-320 is approved in the Wag Aero and Copper River STCs for the PA-20 (so is a 160 by another company). I don’t know why the O-320 works out so well in the Pacers, it’s only another 15 hp.

The big question is that I have found several narrow deck O-320s for sale and wondered if that engine is any more or less worthwhile than the wide deck version. [Read more…]

Troubleshooting a rough-running engine

Q: My Lycoming TIO-540 engine on my Cessna T206H is running very rough at max power setting. I recently replaced one dud cylinder due to very low compression. The ring gaps were wide and exhaust valve guide and seat were bad. Presently all compressions are good, ignition timing is good, and turbo giving boost. The prop looks OK. The engine has TT of 375 hours. The plane is AOG in a remote location. Any ideas?

COLIN WARD, via email

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Buyer beware

Please help me! Some of you who know me are probably saying I’ve needed help for years, but this is something even more serious than helping some old guy who’s been in this industry for a long time. I’m asking all of you to do your small part in getting the word out about the importance of getting a good pre-purchase inspection before buying an airplane.

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Ask Paul: What is proper timing for my engine?

Q: I am an Italian homebuilder of a Van’s RV-3. I read on the Internet that you are an expert of Lycoming and I want to impose on your kindness. I am ready to make the timing on my Lycoming O-290 D2 but there is a little doubt about the timing degrees because the O-290 is not a common engine in Italy, as it was used only by the Italian Army in a PA18. An AD issued in 1954 changed the timing at 18° (label on engine) to prevent detonation, probably with 80/87 fuel. If I use 100LL, will I have to change the timing? Many thanks in advance and sorry for my bad English.


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