which spark plugs to use?

hey guys. ive had my SC on for a few hundred miles now and its already fouled the plugs. i had it dyno tuned but its still running rich (i can smell it and the exhaust pipe gets black really quickly). i havent dynod it since the tune nor do i have any way to read the perameters of the engine i.e. tuner cat.....

so the question is....which plugs do i use and at what gap (i currently have stock 100,000mile platnum plugs in).

also, what do you guys recommend for the running rich problem cause this changing plugs all the time stuff aint cool. im running vortech's T-rex pump and FMU. should i put a switch to the fuel pump and just have the stock pump flow through the T-rex pump and then flip the T-rex on when im gonna put my foot in it?

any tips on the easiest way to change these LT-1 plugs? :cry:

thanks fellas

well first i wouldnt be running platnums. Second headers helped changing plugs. Last i would go back to the tuner and ask him about the car being rich

what is a good non-platnum plug and what is the recommended gap?

autolite 104. I gap mine at .042 with 12# of boost. Some say to gap smaller so the spark doesnt blow out but if you have an aftermarket ignition, youll be alright.

how bout the denso iridiums..i heard good things about them...and also..NGK tr7's?? if im wrong someone correct me. :confused:

The autolites are cheap and easy to find and work well, NGK TR6 is about the same.....

I'm running AC CR42LTS plugs, I believe (been awhile since I changed them out), I definitely remember gapping them about .030 though.

I was having problems with the spark getting blown out at anything over about .032 at about 12 psi on the stock ignition system. As was said though, if you have an aftermarket ignition, I would gap them at around .040.

Run colder plugs and definitely not platinums.

thanks for all the imput everyone.

i am running the crane hi-6 ignition with boost retard so ill gap them around .040. But why does the spark get blown out with the aftermarket ignition?

and will the reduced timing from the boost retard cause the chance of the spark being blown out greater?

spark gets blown out from 2 much cylinder pressure. Keep your gap closer and you will not have a problem.I run the ac r42lts plugs as well.

Your Crane aftermarket ignition provides a hotter spark, allowing it to jump the gap under higher cylinder pressures. Even so, I believe your blower kit directions suggest you run a .035" - .040" gap. Platinum plugs retain more heat than copper plugs, thus contributing to premature ignition (igniting the fuel mixture prior to the spark plug actually firing) which will cause engine damage. I prefer the Autolite plugs over the NGK as I don't like the threaded caps on the NGKs. Seems like they never fully tighten down. Certain headers like the MACs provide improved clearance for spark plug access. Not all headers improve spark plug access.

thanks OBE1, i live up here in bakersfield california so im kinda limited on what i can run as far as headers. what kind are you running?

also, as far as plug access, this after cooler is going to have to be removed to get to the left bank right????? any vortech aftercooler people have any tricks? actually its not the aftercooler itself but the hoselines around the brake booster that are a pain in the rear....

thanks again guys for the imput, and i hope this post makes sence......ive got a cold and ive been suckin' down grandpa's cough medicine if you know what i mean.....hehehe

JBA makes a set of 1 5/8" smog legal headers; they're a bit pricey but well built. 1 5/8" primaries is a good size for around 400 HP. SLP makes a smog legal set of 1 3/4" primaries if you plan on 500+ HP. I know some guys that run the Mac 1 5/8" headers here in California; although the Macs don't have a CARB number, you can get a CARB number from another set of headers and show this to the smog inspector. The Macs have the best spark plug access and are a mid length header, where as the JBA and SLP headers are shorties. The mid length headers will provide a bit more power.

You don't need to completely disconnect the aftercooler to get to the plugs. I remove the intake and output tubes that connect to the aftercooler and leave the coolant lines connected. You'll be able to reposition the aftercooler "head" with the lines connected.

I am wondering if running way to fat is causing some spark problems?

spark gets blown out from 2 much cylinder pressure. Keep your gap closer and you will not have a problem.I run the ac r42lts plugs as well.


you run those on your TT setup? cuz im going with a T88 with a sh*tload of boost..and i was wondering what the best choice would be also...

I am wondering if running way to fat is causing some spark problems?

what do you mean by fat?

i priced the autolites at Autozone today and they guy said they are only $1.09 each....that seems really cheap to me. are these the right plugs or is the guy looking up the wrong ones?

also, whats the deal with iridium plugs.....any good? they are pretty expensive...

lastly, what are the advatages and disadvantages of using a colder range plug???

what do you mean by fat?



Running too rich. Throwing way to much fuel in (below 10:1 AF).

yeah, i think its causing my plugs to foul out. i have another thread in this forum about switching from my vortech FMU to larger fuel injectors so i can get a more accurate tune.

I'm also in CA and have to smog this month. I'm running AS&M Mid-length headers but will try to give them the CARB # off my old edlebrocks to pass. As far as plugs the AC CR42LTS worked for me at .035 and I'm currently running the NGK TR6 gapped at .035 and haven't had any problems. I think the AC's art a couple of heat ranges colder while the TR6's are one range colder. The colder plugs are needed due to the forced induction. Don't use any platinum or iridium plugs with a blown motor. Actually running a blower also helps to pass smog.