Proiroc

Hi! what heat range do you go with? i am @ 5 on my procharged 383. And plugs is all black dusty.. To cold plugs or bad fuel mixture? Procharger recomended NGK 7938 gapped to 29

305sbc

iTrader: (3)

Cold plugs will need a leaner than stoich AFR for idle and part throttle.
they will also need periodic cleaning.
Just sand-blast the tips, then cook the tips for a minute or two with a propane torch to burn all the fuel byproducts and moisture out of the insulators.

If you are running EFI, then make some adjustment to your time-out fueling after start-up, your warm-up enrichment, and make your DFCO more aggressive.

To run leaner than stoich you will have to run Open-Loop.

The above changes will extend the period between cleanings greatly, but you'll always have to clean the plugs periodically.

calebzman

iTrader: (3)

I'm guessing that you are too rich. I'm running Autolite 3923 plugs at .035 gap for 10psi. They are one heat range colder than the ones you are running (NGK 7938 = Autolite 3924). My plugs always look perfect, but it seems like they need replaced about twice a year anyways. From info in the post above, it could be because I don't clean them, but I figure if I'm gonna take the plugs out for any reason, new ones are going back in.