Which Spark plugs?

[Danny's 94Cobra]

Does anyone know which spark plugs I should use for my application? I have a 94 cobra with a fresh 306 with low compression pistons, Trick flow track heat heads, Vortech S-trim 10-12 pounds with powerpipe, Msd ignition with boost retard, 255 intank and T-rex. I used to have the cast iron gt 40s but switched to the Trick flow and now I don't know which sparkplugs to use. I would like to stay with Autolite since I had no problems with them on my gt 40s. I know you are supposed to go 1 or 2 steps colder than stock with a charger but what is stock with these heads? Need to buy spark plugs arlready so any help would be appreciated.

 

[TMC]

You need an NGK No. 9 but you can get away with Autolite 3923's which you should be able to get at Pepboy's or somewhere else local pretty easily.

 

[GRGT1994]

You checked wirh MSD?

 

[a50sn95]

3923's for me gapped at 30-35.
I couldn't find an NGK #9 on the websites I looked for it at. (Summit has 5 pages of NGK Plugs...)
No Platinum plugs according to Vortech and Paxton unless it came with platinum from the factory.
I don't know the reasons, although I think it has to do with the extra heat created by a Supercharger (Or N20 too).

 

[a50sn95]

Oh Trick Flow's website says (here):

Spark Plugs:
AC FR3LS
Autolite 3924
Champion RC9YC
NGK-FR5

 

[VibrantRedGT]

3923's are two heat cycles cooler than stock iron heads. I used these gapped at .035 with MSD BTM, MSD blaster coil, MSD plug wires and never had ignition problems.

 

[Danny's 94Cobra]

thanks for the info

Thanks for the info guys.

 

[KenneBell]

I have had two supercharged 5.0's and the best plug by far is the NGK UR5 that is one heat range colder than stock and I noticed instantly more power with the NGK's than with autolite. Granted a little rice but hey the plugs work great!

 

[Green 94 5.0]

Autolite 3924's for me.....