Farmall Ignition - High Compression

Well I finally got around to getting my Super M back together. It has 175 psi of compression. As expected it will run but not proeprly on the dyno. I figured I would need electronic ignition. I have never installed one. Select Parts has an electronic ignition assembly and 45,000 volt coil. What do I need for wires and plugs? I have been told that with elctronic ignition that only certain plugs will work properly. Any advice you have would be very helpful.

We use 386 Autolite plugs with our petronix ignition

Use a ballast resistor! It will double the life of the electronic IGN, and coil, will still have a hotter spark than points!!! Chad

What brand of electronic ignition is the best?

Larry, the plug ratings are more a function of their heat dissipation characteristics then what type of ignition you have, so the heat range of the plug is what you need to be concerned with and what to run may not be all that different then the stock plug.

Nowwwwwwwww as compression increases, it takes more voltage to arc current across the plugs gap, so a high energy ignition with a high voltage rated coil may well be in order. Then once you have BOTH an elec switch to handle the higher energy coils current,,,,,,,and a coil that can achieve the higher necessary firing voltages,,,,,,,,,its typical to also use a wider then stock plug gap for a WIDE FAT HIGH ENERGY SPARK woooooooooo hoooooooo.

Still the heat range of the plug can be the same as a stock plug, its just that you can get by with running a wider gap if you have an elec switch and higher voltage rated coil.

NEXT if you dramatically increase the firing voltage (due to more compression and a wider plug gap) you need good quality higher voltage withstand rating plug wires and a good quality distributor cap etc. Still a good quality set of stock plug wires can likely withstand the higher operating voltages buttttttttt when you drastically increase compression and run a wider plug gap and higher voltage coil, its good to use the quality higher voltage rated plug wires.

John T

I put the petronix elec ign and high voltage coils (from this site) on my 140's and a cub. Used stock plugs but increased gap to 0.040 in.. Note: one elec ign went bad after 2 yrs (it wasn't tightened down properly) and I now keep a spare. Had to use high voltage plug wires (from Brillman Co online) because it looked like a light show at night around the dist/plugs/coil with stock wires. I highly recommend this set up.

Old rule of thumb from racers was that with a high-compression engine, you want "an ignition system you could weld with."