Spark Plug Heat Range And Gap For 30-32 PSI

[earlbrown]

I believe the UR4 is the cross reference to 42's and 43's.

The heat range on NGKs goes up to 10. 10 being the coldest.

[Steve Wood]

I was thinking it was a 6, but then thinkn says it all

[larrym]

I have been using UR5s and YR5s the YR5 is the same plug with a non projected tip.
I use Bobs TR6 ignition and LS coils and gap them around 35 but don't run much more than 27 psi at the track I'm a coward.

[Scoobum]

Brad - I always ran 42's in my car, 43's were too hot, i wouldn't get KR but it'd break up at high boost with alky - you could tell it wasn't happy.


NGK is the plug of choice for me - they are easy to read and seem to be the highest quality copper on the market. I buy them in bulk from rock auto, they are cheaper than anyone. Shipping might kill you.

If I'm going to spray the car gets a fresh set every time out, and I change out my hot cylinders before a pass, and read them after. Depending how they look I'll change the tuneup accordingly and after a few passes I'll change all of them out.

Jeremy...did your car idle like crap with the 42's? I tried them once...and mine did. Figured they were too cold to fire at idle? My buddy Mike with the 2002 nitrous Camaro cuts a plug open after every run with a zip wheel to check it.

[nocooler]

Yup cold start always sucked - once it was at temp it was ok.


I remember spending hours with translator and chip settings to get it dialed in. I had the translator on full lean idle and added 4-6* of timing to the base table via the translator. And then pulled the timing back out via low gear and high gear timing. It helped but there was only so much I could do.


Maybe Eric has a chip or setting to clean the idle up - I haven't kept up on things.