Plug/gap for my setup... been using TR6's
 

Currently making 425/445 with my 408 N/A setup but the heads are out getting ported right now. I hope to make somewhere near 500 (or at the very least 475) when I get them back and everything bolted back up. Just wondering what plug/gap I should be using for this kind of power as I have been using TR6's. As you might notice, my power is a little below what it should be which has been assumed to be due to too low of a DCR with my cam, but it could be any number of things. Could the TR6's possibly be robbing me a bit of some hp? If they are the correct plug for this application, should I leave them at the stock gap of .035 or gap them higher? Just trying to find out the specifics for my particular setup.

ive heard of .038 being done before...

I've seen a lot of people gap theirs to .038 but their setups have ranged from 375rwhp N/A to 600 on the juice. That doesn't really tell me much about what my setup in particular would work with best.

lol well damn...u might wait a bit for someone with ur exact setup...those plugs work fine, if it was a na motor id go with ac delco iriduims but thats here nor there...

artic, thanks for the help. as far as plugs go, I run a .038, like you said for spray. what is your compression ratio? this is the major determining factor for your plug type and gap. If you are running a 11 to 1 ratio, I think I would be using the tr6's, if you are still in the mid to low tens, you might as well go back to the tr55's. I doubt the will be any power gain for it, like 1 hp maybe. Need some more info.

I'll be running about 11.3:1 SCR with a DCR in the mid to high 7's.