Spark Plug Heat Range

whitey said
I found a website sometime ago that had a PDF file on 'Speed Tweaks and Tricks' and for Magnum engine (Since I retrofitted Magnum heads to my 360 LA). And it mentioned using AutoLite 3923 plugs...

"While the factory and factory replacement spark plugs work, the Magnum engines have shown slightly better performance with the Autolite 3923 Spark Plugs. The Autolite 3923's are a standard tip spark plug that is one heat range colder than stock, as compared to the "Special Power Tip" plugs that the engine came with. Why the Difference? A standard tip is less susceptible to detonation, is a good replacement for modified magnum engines, and work very well with modified engines as well...especially when using nitrous or a supercharger. In some cases, the Autolite 3923's also showed a 4-5 HP difference at the rear wheels on the Dyno. (The test was performed with new OEM Spark plugs vs. the Autolite 3923's. No changes to the engine and the plugs were tested on the same day under the same conditions.)"

I've been using them with MSD 6A and wires and running fine.

I read that article also. I used to have a 93 Dakota with a 5.2 magnum and over the yrs. I tried a few different plugs in it to see if I could tell any difference. I didn't have a dyno to go by or drag strip time slips, just seat of the pants and mpg but when your used to driving something everyday you can get a feel for changes. I found 2 plugs that did seem to perform a little better than the original Champions and the Autolite was one. Equally as good was a NGK V-power and they seemed to last longer than the Autolites. The first aftermarket plug I tried was the Split Fires. That's right when they first came out and I let the hype get to me and wasted $40 on a set of spark plugs. They didn't run any better if as good as stock plugs. I think it's because the dual electrode shrouds the flame front but that's just my theory. Knowing that voltage takes the path of least resistance to ground it makes sense that these plugs are nothing but an over priced gimmick. I later added a MSD and found it ran better with the plugs gapped at .045 and also got a little better MPG.