Fouled plugs

[8466]

I recently did a run up and found a 150 rpm drop on the right mag. It had been steadily getting worse. I have been flying just in the pattern the last 5 hours so maybe the plugs are fouling Bwi haven’t flown it at cruise, high power setting afor a a hour or so which may clean out the plugs. Could this be so? If not after correcting this fouling what should I do in my flying habits to prevent this from happening.

Thayne

[8451]

I recently did a run up and found a 150 rpm drop on the right mag. It had been steadily getting worse. I have been flying just in the pattern the last 5 hours so maybe the plugs are fouling Bwi haven’t flown it at cruise, high power setting afor a a hour or so which may clean out the plugs. Could this be so? If not after correcting this fouling what should I do in my flying habits to prevent this from happening.

Thayne

The number one thing you can do to prevent fouled plugs when running 100LL is to lean aggressively on the ground. If you’re able to apply takeoff power and the engine still runs you aren’t leaned out enough.

As a side note, such practice will ensure you always set the mixture full rich (or altitude appropriate) before takeoff, and not accidentally take off at an engine damaging reduced fuel flow.

This practice applies to any piston aircraft.

[4390]

You can't lean a Stromberg at idle speeds. Check the idle mixture. You can change to a Marvel, they can be leaned, or try fine wire plugs.

[6643]

You can change to a Marvel,

For that money you could pay someone to clean your plugs before every flight for the rest of your life!

Champion REM37BY plugs are specifically designed to help prevent fouling in Continental C-series engines.

[6930]

I run TCP in my fuel and that helps a lot. I pull my plugs and clean/Regap them every 50 hours. Without TCP, I was pulling a lot of lead out of the plugs (1/2 a thimbleful!). With TCP, they are MUCH cleaner.

I also lean the mixture one finger width any time I am flying (not at takeoff) when it is hot on the theory that the air/fuel mixture is richer than when flying in cold, dense air. It is hard to quantify the impact this leaning has but between the TCP and leaning protocol, the lead issue is under control.

I have a Stromberg carb, and as someone else mentioned, leaning on the ground has no effect. Some will say that leaning with a Stromberg carb in the air is a waste of time, but I don’t think so. If you pull the mixture out slowly when flying you will get to a point where the engine starts to balk from over leaning....so it is doing something.

One other thing I do is to change the oil every 25 hrs or so. That keeps the lead that goes into solution in the oil under control. Have nearly 10 years of Blackstone tests for my engine oil and it has become clear that the longer between oil changes, the more lead in solution in the oil. There is a direct correlation between the two. The oil filter will not capture the solvable lead. The only way to get it out is to change the oil.

I had a stuck valve issue with my plane back in 2011. Ended up with a very expensive overhaul. 900 hours since the overhaul, and following the protocol noted above, my engine is running perfectly.

Hope some of that helps.

Mike