I primarily use Champion Iridium plugs. I also have 1 Autolight Iridium plug.

I believe that the Autolite plugs are now Tempest.

I have over 1,000 hours on the plugs and they look like new except for one problem. After about 500 hours the Champion plug resisters gain resistance. The resistance should be about 2,000 komhs. This resistance will grow in the Champion plugs to over 20,000 ohms. When it gets over 5,000 komhs the plugs will not fire when wet (at engine start). I found that 6 of my 8 plugs were not firing. I obtained good resisters from some standard plugs and now the engine starts up immediately, again. Another problem is that the mag coils were burned out after the resistance gain. I had to change the mag coils.

The Autolite plugs, on the other hand, never gain resistance. Get the Tempest Iridium  plugs.

Most aircraft never see the resistance gain because the plugs don't last over 500 hours but Iridium plugs will last the life of the engine.

The Iridium plugs also are gapped to 23/1000 instead of the standard plug's 16/1000. These plugs, therefore have a bigger spark.

My last 100 hour plug change showed that one more Champion plug resistance had grown to over 5,000 ohms and was very wet and dirty. I swapped it's resister for a good one and all is well again.

For plugs, try Linda Lou out of Memphis. I know that she has the best price on the Autolite plugs. Hopefully she also sells the Tempests. Her number is: 901-365-6611

If you have any questions or problems feel free to call or eMail.

Sincerely,

Feathers