I have read several threads in the past but would still like some fresh opinions. I have 454 Mag EFI with M1-SC Procharger. I Have been running this setup for four years and I Programmed it with MEFI Burn. It seems to be falling out of tune a bit lately and has begun to miss intermittently. Before I start re-tuning, I'm going to change out my plugs and do comression check. I have been running NGK UR5 plugs but I get the feeling they are too cold.

What do you all recommend for plugs on a setup like this?

bigger question is why in the world would a program "fall out of tune?" I would look into wear items like injectors, plugs, wires, etc. not so much your tune

Thus the compression check and plug change which naturally goes with cap, rotor and wire check.

I was not suggesting the actual program changed, more the "wear items" have as you sugggested.

I guess "fall out of tune" is not a good phrase for some but my question is about the spark plugs.


What do you recommend for this setup?

NGK R5674-8 or ac mr43t is what i've seen the most on that engine..Sure others will pop in with ideas

The UR5's are what I ran in my 525SC. They have the same heat range as an AC R41T. They really should not be too cold.

Huh, now that I read NGK's site their heat range is 2-12...2 being hot and 12 being cold... guess 5 is actually 1 step hotter than the stock BR6fs.

I also remember reading on here once that projected tips are a no no for forced induction. Im totally confused now.

NGK 5673-7. THat's what I run.

What gap ? Stock says .026... seems small.

Lot's opinions on gap. We run .035 plug gap w/Crane Marine Ign box.
IMO, the answers on plug gap will be similar to the nunber of responses you will get on how many PSI air to put in your trailer tires.
...oh, we run 45 psi.

The UR5's are 1-2 heat ranges cooler than the stock BR6FS's.
The extended tip is very slight and I never had any issues. I was running almost 8# of boost.