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Another auto plug question

T

togaflyer

Well Known Member
Getting ready to do my Surefly mag install with an auto plug harness conversion.

Engine is an IO 540 with dual impulse mags. Replacing the right Bendix mag with the Surefly. The current Bendix mag harness (right mag) feeds the top 1,3,5 and the bottom 2,4,6 plugs.

So question is, should I install the auto plugs with the current configuration (right side top and left side bottom), or all auto plugs on top or all on bottom. Some have said put the auto plugs all on top to prevent the chance of fowling. But I m not sure if those who recommended that was running an IO 540 or they have a four cylinder with a different harness configuration.

Also, I know the spark doesn't care if it from the top or bottom as long as it’s the correct cylinder. Just want to find out what the norm is when it comes to auto plugs and harness set ups.

Thanks much!
 
togaflyer said:
How would the mag check differ between the plugs being located on the top vs the bottom?
Click to expand...

It wouldn't.

The 320 has one EI and one mag with the EI plugs on top. It doesn't really matter. However, if you run rich a lot and have plug fouling issues, I would put the auto plugs on the bottom, as they will likely take more lead before shorting. For some reason, the bottom plugs seem to get more lead than the tops. I lean agressively, except on the ground, and in 850 hours never had a fouled plug (occasional lead shot piece or two that gets removed though)

I believe the Lyc wiring recommendation has more to do with the simplicity of the rotation schedule. With a mag, half the plugs fire + to - and the other half - to + This means that half wear the center electrode and the other half the tabs/shell and the plugs must be moved to the opposite for best wear characteristics. The mag does not have a commutator, therefore produces AC.

Larry
 
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