91familyxj

what kind of spark plugs should i run in my 96 limited 5.2. I know in my xj I just ran copper core champion but I wasnt sure if there is something better for the 5.2? Thanks

91familyxj

my book says to run RC12YC but what are you guys running in yours?Thanks

dnuccio

i use champion RC12YC gapped to right around .037"

91familyxj

thanks I was thinking of just going with them but I have to ask why gapped to .037 and not .035?

Wandering XJ

Wider the gap hotter the burn!

dave1123

Okay, remember this. it's going to get wider as it older. Also, it takes more energy to flash a wider gap, especially at higher clyinder pressures. That's why plugs missfire at full throttle but seem to run fine at lower speeds.

Also, remember this;
Champions in Mopars
ACs in GMs
Autolites in Fords
Imports---well, anyway.

Nothing else seems to work for long!

dnuccio

might just be my perception, but with that slightly wider gap, it seems to run ever so slightly smoother

dave1123

I think you are imagining it. Give it a week, and .035 will be .037

ol"blue

This comes from the ZJ FSM:

SPARK PLUGS

ENGINE;----- PLUG TYPE;--- ELECTRODE GAP

4.0L 6-CYL; -- RC12LYC;---- 0.89 mm (.035 in.)
5.2L V-8;----- RC12LC4;---- 1.01 mm (.040 in.)
5.9L V-8; ---- RC12YC; ---- 0.89 mm (.035 in.)


Note: Always use the Tune up specs listed on the Emissions label on the core support of your vehicle, if different from those listed in the manual.

*Mine agreed with those listed for a V8 ZJ, and so I used those plugs gapped at 0.040" with great results.

mudfrog

I can't find the Coppers on Advance's website anymore. I have always bought them there. Anyone else notice this?

stock95sport(for now)

a wider than recommended gap is also more prone to getting "blown out" by the cyl pressure before ignition. but a .02 is negligible anyway.

mudfrog

I run .040 but I have a decent coil.