Rosco the Iroc

I've just rebuilt my L98- it is a true one with vette heads now.
It's got 10:1 and I'm running a 6AL and GM type blaster coil.
I'm still tuning it and I'm worried about my setup.
I'm running stock heat range and a .050 gap.
Should I change it and if so how?

OMINOUS_87

With the smaller chamber and higher compression I would run 1 heat range cooler. Try out an NGK UR5, it should do you just fine. What are you running for a cam?

Rosco the Iroc

Crane Powermax 3032.

NastyL98_T/A

NGK TR55's or Autolite 103's.

Rosco the Iroc

thanks will do- now should I gap to .060? What should I look for to tell?

Nasty_Bird_'90

I'd gap them at .050-.055

kevinc

Not sure he'd want to run tapered-seat plugs on aluminum heads designed for flat gasket-seat plugs...that "T" in the NGK part# stands for "tapered". It'll not seal well, and likely damage the head's sealing surface.

I ran NGK FR4 and Bosch FR8DPX plugs (stock heat range, the Bosch'es were platinum) on my 'Vette L98 heads with no problems, nice coloration and good longevity even during track use. The Bosch platinums felt a wee bit better on the butt dyno but made no improvement in 1/4mile times.

OMINOUS_87

kevinc is right! Totally forgot you were working with alluminum L98s, you need a gasketed plug. I would try the NGK FR5 first. It is still 1 heat range cooler then stock and should work well with your compression and cam. Start your gap at .050 and work from there as you pull your plugs for inspection after some burn in miles.

kevinc

Some additional info I dug up out in the garage from recent experimenting...since swapping to AFR heads the stock heat-range plugs were reading like they were a tad too hot and #4 was cracking the insulator cone during racing so I started researching options.

Only supply of non-stock heat range plugs I can get locally is Autolite www.autolite.com so I dug up the following:

#3926 stock heat range
#3924 one heat range colder
#3923 two heat ranges colder

No such part# as a 3925 for some reason.

I'm currently running 3923 and they read fine thus far, not glazing up or cracking like the FR4 or FR8DPX did but I haven't had it back on a road course w/ them yet.

They're $1.49 per 2-pack @ WalMart, I'm running mine @ 0.040" gap w/ my all-Delco ignition. With hotter aftermarket parts like an MSD box or coil you should be able to up the gap.

TRAXION

I'm running exactly what Kevin is running. What's up Kev? You appear to be in a good mood today

Tim

kevinc

And I got the initial point to the Autolites from TRAXION, so props right back at ya.

Strangely, I posted this and the thrash at the other guy on the same day...musta been that caffeine withdrawal finally passing.

Rosco the Iroc

Thanks for the corr info.
:hail: