Changing Spark Plugs; what should I know

[EricJ]

47 minutes ago, N201MKTurbo said:

I believe the no go gauge is a scam to sell more spark plugs. Is that gauge mentioned in any ICA?

lol...could be.

It's mentioned in the Champion Aviation Service Manual that covers spark plugs, but not in the Tempest maintenance guidance, which says:

"UREM37BY can be gapped until the electrodes are worn to a point where it becomes difficult to properly adjust the gap."

It doesn't give much guidance beyond that for other plugs. 

[Shadrach]

A lot of good advice here. I’ll add that it’s a good idea to have a stable, protected, tray to place the plugs after removal to ensure they cannot fall or be dropped.  Make sure the plugs are labeled so that rotation and any potential issues can be correlated to the position from which they were removed. Rotate plugs as described in the Tempest Installation and Maintenance Manual. 

Regarding fine wire plugs…..Warning - heretical opinions to follow:

If your engine starts and runs well with massive plugs, you’ll not likely notice much benefit from fine wires other than some degree of additional service life. I typically get in excess of 800hrs out of a massive plug and I remove them from service based on appearance rather than any noticeable degradation in performance . The only reason I have ever replaced massive plug inside of 500hrs is for QC issues. If rotated and cleaned every 100hrs, massive plugs offer excellent service life. 

As far as engine performance goes, most stock Lyc IO360s run smoothly on massive plugs at mixture settings quite a bit leaner than practical for the available MP. I would reap no benefit from the ability to run leaner. I can already run 20° to 50° leaner than is practical for just about any available manifold pressure.  

My engine is easy to start hot or cold. I can’t imagine it being much easier to start, but perhaps fine wires would make for easier starting over a broader range of air fuel ratios allowing for less reliance on precise technique.

Show me a plug with a performance delta that I can identify from the cockpit without knowing it’s installed and I will evangelize with the rest of the congregation. For now, I view fine wires the same way that I view nitrogen filled tires. Is there some benefit? Sure. Is it significant? Probably not for most applications.

 

 

[thomas1142]

I had to have the maintenance shop change the plugs, but I was right there ready for the next time.