Ask Paul: What’s going on with my spark plugs?

PaulMcBride

Q: I have a 1962 Piper Cherokee 160 with the O-320-D2A engine. The engine had a complete overhaul in 1992 and only 500 SMOH. In addition, 20 hours ago the engine had an annual in which an oil change was done, new plugs, and compressions in the 78/80 range.

What I have noticed is when I taxi the airplane without flying it (I always lean on taxi), the next time I do a run-up the left mag performs poorly and I have to lean and “burn off” whatever is getting on the plug(s), then the airplane runs fine. This has happened to me twice recently. [Read more…]

How to break-in your engine

PaulMcBride

I recently received a letter asking about engine break-in following overhaul. This is a subject that should be of interest to everyone, even though you may never actually have the opportunity to break-in an engine during your flying years.

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The importance of keeping current

Q: I have a Glasair with a Lycoming IO-360-B1E engine. After reading your article in the May 11 issue, I tried to get a copy of Lycoming’s SI1325A to see if I should change the timing from 25 to 20 degrees BTDC, but was not able to find that instruction. Can you help?

RON WALTERS, via email

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Ask Paul: Too much information about our engines?

PaulMcBride

Q: I have a factory reman Lycoming O-540 E4B5 with 300 hours and 2.5 years on it. At idle (1,000 rpm), my JPI is showing alarms on the #1 EGT for having a large differential — #1 EGT is only 600° while the rest are 1,200-1,300°. Above 1,500 rpm and higher everything seems fine with normal readings and maybe #1 CHT a little lower, but I expect that since it is first in the airstream. I have full data printouts from the JPI.

I have checked the plugs even though my mag checks are fine and replaced the probe on #1 EGT with no change. I’m scared to think I have stuck valves. [Read more…]

The marriage between piston rings and cylinder wall

PaulMcBride

Q: I am an A&P, and have been in aviation since 1990. I once worked with another mechanic who told me that if you pull a piston out of a cylinder, you must replace the rings and hone the cylinder. He is the only tech I have heard say this — until I read your article What’s best? A flush or overhaul?

You stated: “If oil starvation is suspected, you may want to remove the #1 cylinder (leave the piston in the cylinder so you don’t have to hone the cylinder and install new rings) and remove the connecting rod from the crankshaft.” Can you explain this? Is there a Service Bulletin or other directive that explains this practice? Thanks for sharing your knowledge with us.

TOM THROSSEL, via email

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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…]