Mods are 383 eagle forged crank, forged pistons and rods, over the radiator CAI jethot longtubes and custom true duals with h-pipe dumped, comp 1.6rrs ported LT1 heads (flow 270/190)
ported runner LT4 intake, EWP
42lb green top ford injectors
custom grind cam by alan futral 238/245
58mm BBK throttle body
all emissions stuff deleted

Developed a miss a little after I changed plugs. I floored it to 6,000 a few times and it MOSTLY cleared up. Really only does it up high in the RPM's now, but before I floored it, it would do it all over the RPM's even down low. I think I should try TR55's. Before I changed them, it had the TR5ix. Only things I have done are swapped with a good stock coil, and inspected wires at night. Didn't see anything, and coil didn't help. Plugs have about 60 miles on them.

 

 

Check the gap on that one that is fouled (black). It's likely too wide for your application. You shouldn't have that kind of issue just from swapping to a plug with a heat range 1 colder. I would replace the fouled plug and double check all the gaps and then check the header temps with a heat gun at idle and at a steady 3k rpm. Could be the injectors just need a slightly different multiplier.

 

I gapped them all at .45. Was that too wide? I don't have a heat gun to check header temps. The tune has been checked again. I was told it looked fine. IDK, it seems to be getting better the harder I drive. The car was sitting basically for almost 4 years, just driven once a month around the block but when I did start driving it a few weeks ago and even over the 4 years I don't remember it misfiring.

 

I just re gapped to .35. That black was no longer. I guess the last couple of times I floored it it cleaned it off. They all looked really good. Ill see how it runs tomorrow.

 

Run them for a day or two and pull the plug from the hole that was previously gunked up along with one or two other plugs and see how they look. .035 may be a bit too small if you're just driving around on the street.

 

Well I read .35 is a good gap for a 383, and I just checked the old plugs and they were at .35 too (I never checked them before).

 

Displacement isn't really a factor. It's more about compression, ignition, fuel type... that sort of thing.