Coldest Plug

[Oldschoolpony]

Whats the coldest plug that will fit a set of Dart heads? They're the deep plugs. Im hooking up a 175 or 200 shot(wet kit) and want to get the coldest possible plug. (track car, for the most part only)

[ultraflo]

Aluminum Darts? ...if so, here's some info to check out:

Here's how it goes with Autolite from hot(1) to cold(6) in a 14mm thread 3/4" reach 5/8 hex shell. Although you can get hotter, I'm gonna start at a Autolite 3924


1) 3924/AR3924 - projected tip, resistor
2) 3923/AR3923 - projected tip, resistor
3) 3922 projected tip,resistor - AR3935 standard tip,non resistor
4) 3911/AR3911 projected tip,non resistor - 3934/AR3934 standard tip,non resistor
5) 3910/AR3910 projected tip,non resistor - 3933/AR3933 standard tip,non resistor
6) 3932/AR3932 standard tip,non resistor


"You should always try to run a projected tip if clearance allows as it brings the plug out further giving a quicker more complete burn and is a self cleaning plug meaning it won't foul as easy. As you can see the 3933/AR3933 is one heat range warmer then the 3932. The NGK BKR6E crosses to a Autolite 3923/AR3923. The NGK BKR7E crosses to a Autlite 3922(for some reason they do not make the AR version in a 3922). Personally I feel the 3932(NGK 10) or 3933(NGK 9) plug that you are using is way to cold for the setup you have and if you have a flat top piston you should try to run the projected plug,but if they are not fouling it probably won't hurt a thing. For your setup I would run the Autolite 3922 or 3911/AR3911. For 10.5:1 compression 200 hp shot you shouldn't need anything colder then the 3911. Those 3932 and 3933 will probably foul out on you if it gets cold out or you are running rich it won't have enough heat to burn off deposits and you'll be shooting ducks all the way down the track. The idea is to have a plug that is cold enough to prevent preignition but hot enough to stay clean. When working with Autolite trying to find the optimum plug we use thermocoupled plugs to tell us the tip temp so we don't get into preignition. These special plugs allow us to make sure we have the optimum plug per application in production. Us racers unfortunatley have to start cold and if it doesn't foul you're at least safe. Hope this helps , DAN" ...from another mustang forum.

My .02 cents on the matter... I currently run an NGK BKR7E w/ a 200 shot. The AR3932's and the NGK plug that crosses with that number are what I ran before switching to a warmer plug due to fouling... I may try one step colder than what I run now to see how things go as I'm still sorting out my combo w/ a 200 shot. After making a pass, the ground strap is grey to brown in color...

Good Luck! ...and as Dan stated "hope this helps"

[Oldschoolpony]

Iron heads. Im still in the dark ages...lol. Not really. AFR 205's will be installed this winter with alot more cam than the comp hr292 cam. Ohh, BTW its on a 347 with almost 11 to 1 comp. and a zero deck block. (if that makes a differnece.)

[ultraflo]

No biggie, just tryin' to help...

In that case, you could give NGK a call... 1-877-473-6767

You'll get a message prompt... just push 2 twice and that'll take ya to spark plug tech, a gentleman by the name of John should take care of you.

Otherwise, maybe someone here can help you

I'm not totally sure but if I recall correctly... for Autolite, it's like 24, 23, 22, for iron heads. I'm new to NGK's so can't help ya there. Nitrous Express referred me their way...

seems to me your best bet would be to call John @ NGK

Take care...