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Adapting Automotive Plug wires to Magneto caps,  

By: Dave Hanson

For those of us that have spent $145.00 to $199.00 for one set of spark plug wires just because they are used with a magneto, there's an alternative solution that many, including Dave have used. It is much cheaper and offers the aircraft owner the option of what plug wire colors he is going to install. In addition, you don't feel like you've just been bent over by Superior or any other Magneto plug wire manufacture. Read on as Dave explains the process.

What the heck is that? Want to make a new ignition harness and use automotive plugs. Well some do and some don't. here's how to do it if your interested in trying it. Not cheap, about $13.00. Plus wire labels. I like them, its just easier when your grabbing wires to have them all labeled.

See T 1 means top of cylinder the No 1 cylinder. Oh yes, here is the part number for the Accel universal plug wire set 4039 B, the B is for BLUE color, about $38.00

First drill your old magneto cap to take the 8 mm wires. Make the hole a bit snug to the wire. The wires I'm recommending are tinned copper wires don't use anything else stay with the part number I've provided. I've already validated fit form and function of these wires (4039B), they work. I've used the others and its not a good idea, I experienced weak spark. You will need some small 5mm washers to solder to the wire ends. I made mine using my hole punch and a .030 drill. First I drilled the .030 hole and then punched it out with the hole punch so I ended up with a little copper washer. I uses a thin copper sheet from the hobby store or local hardware. Total cost was about $8.00

Pull the wires thru the cap the distance they will be fully engaged in the plug holes on the magneto. Don't forget to measure wires to proper lengths to the spark plugs then cut off the excess. Fit the center electrode wire thru the small copper washer you just made, fray the end over the washer. Solder the wire to the copper washer so it's secure. Trim excess wire, then clean with acetone to remove resin. Fit the cap allow about 1/8 in gap in the cap then remove and put some tire wraps or zip ties around each plug wire on the inside of the cap to hold the wire at the proper distance. This is required so when you screw the cap down it makes a solid compressed contact.

This plug wire job isn't complete yet. I still have to make a loom but you guys get the idea. So pick up an 8 pack of spark plugs (Autolite 3116). They're about $1.50 each. Gap them from .028 - .030, A healthy magneto will support the plug gap. Voltage discharge is between 15 and 28 kv. Also, you can run Denso or NGK BR9ES or BR8ES plugs by buying the 18mm to 3/4 inch plug insert adapters from ACS or Lightspeed Engineering.


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