Denso Iridiums?
 

Rebuilt 306, with stock cam, speed density setup. GT40P's, ported Cobra upper and lower, 65mm TB, 1.6 roller rockers, exhaust.

Thinking about Denso iridiums, but may stick with the Motorcraft coppers.

Thoughts? Better recommendations? I don't mind experimenting with plugs.

Thanx!

It never hurts to try different brands/gaps on your spark plugs. I usually just use Motorcraft coppers because i've never had a ford run bad on their recommended plugs because of them. I don't think you'd gain much if anything by going with those plugs. One trick i've heard of is filing down the ground electrode so that instead of hanging over the center electrode, the end of it stops at the middle of the middle of the center electrode (looking "top" view at the electrodes). This supposedly unshrouds the spark kernal exposing it to more air/fuel (the idea behind split fire plugs). You can also "index" spark plugs and line them up toward the intake valve or exhaust valve (or anywhere in between) and see if you get some gains by having all the plugs lined up equally toward an area of the combustion chamber that you choose.

Thanks for the reply 84/89. I think I'm just going to put my Autolites in, everything was fine with them. Or, maybe Motorcraft coppers. One car we put the Densos in was not running as well as before. Like anything else, I guess it matters the combination it is going into.

Thanks again