Several months after I'd spent hours securing the ignition harnesses to the engine and carefully routing them around a myriad of obstacles, I came across this discussion warning of the dangers of bundling P-mag ignition leads close together. There actually is a cryptic mention of this in the P-mag installation manual, but the way it's worded made it sound like it didn't apply to my installation. To check the information in the thread I emailed Emagair, who confirmed it but were also frustratingly less specific than I'd have liked when I asked for guidance on how they really wanted me to route the wires.
You may recall when I said "if the P-Mag ever so much as looks at me funny I'll replace it with another magneto". Rinky-dink connector, a history of failures, and now this? Three strikes and it's out of there. I'm tired of messing around with it and wondering if it's going to come back to bite me later. That's just my opinion, and I know plenty of people have used them on their airplanes successfully, but I'm done. Magnetos might be old-fashioned and prone to certain types of failure, but at least they're well-understood, thoroughly documented, pretty reliable, and easy to repair.
I traded the P-mag to somebody who was more eager to experiment than I am, and received a pair of used Slick 4370 magnetos in return. One I put on the shelf for spare parts, and the other I sent to Crossfire Magneto Service for overhaul. Meanwhile, I also bought a new harness (Champion P/N M2992R). That arrived at about the same time magneto came back, now looking brand new.
P-mag removed, good old fashioned magneto mounted in its place. The ignition harness is only loosely routed in this photo:
I used my magneto timing box (visible at right) to get both mags timed to 25° BTDC. It took some fiddling to get them in perfect sync, as it's hard to make very precise timing changes without a certain amount of trial and error. But I got there eventually.
Ignition harness routed and secured properly once again. The plug wiring is now a bit different from before – now each magneto fires the two bottom plugs on one side of the engine and the two top plugs on the other side. The bottom plugs always suffer more oil fouling than the top ones, so it makes sense to do it this way. It seems like this would also tend to equalize the RPM drop from one side to another during a pre-flight ignition check.
The plug wire routing on top of the engine is slightly different from before due to the plugs being taller and having straight as opposed to right-angle connectors.
The P-lead routing for the right mag was kind of a pain – mostly due to all the adel clamps I had to put in to secure this one wire.
I used the same arrangement for strain-relief of the P-lead as I did on the other side – an adel clamp attached to the ground lug with a slightly longer screw and lockwasher. Wiring the right P-lead was made more difficult by the fact that you have to attach the fasteners from the bottom in an area you can barely reach, thus giving the little nuts and washers all kinds of opportunities to fall onto the floor and go skittering off to who knows where. I eventually got it sorted though.
And with that taken care of, it's back to forward progress I hope…