Wanted to see if any one else has had experience with plugs in a supercharged mopar. I hace a 383 stroked to 496 with a procharger and have no idea what plugs to run. Finally getting to the end of my build before the break-in and dyno time! Thanks,rich
Spark plugs for force induction
- Thread starter 68fastop
- Start date
65sporty
Old Man with a Hat
What's the Cylinder head and Supercharger manufactures say? Do each recommend something?
I haven't looked into asking them yet. Thought I'd ask you guys who might have experience with real world situations first. I know sometimes people will have alternate suggestions instead of what a manufacturer might recommend. Thanks,rich
BillGrissom
Active Member
My only comment is you may need to run a smaller gap. My 2.4L was misfiring under WOT years ago. I found a Chrysler TSB for the same engine w/ turbo (Neon SRT, PT Cruiser) that said to lower the gap from 60 mil to 50 mil or such. I did so and the misfire went away. Of course, 50 mil seems large re 1970's spec's of 35 mil, but HEI ignition can jump that. It is easy to throw a spark in a vacuum and hard at high cylinder pressure (i.e. WOT), which intake boost provides.
Like that answer... if I may add... the turbulence caused by forced induction has been know to "blow out" the nucleus flame as it starts. A tighter gap will give a somewhat lower intensity, but longer duration to your spark and help the fire establish more reliably. Copper plugs are often recommended because they fragment, which helps too.
For @68fastop , best I have for you is to test fit a plug to assure that it fits properly, you may need a paper guide, but should be able to find a dimension/heat range chart digitally. You want a plug depth that fits (not to long or short) and the proper seat type... then you can figure out heat ranges. The safest way is to start with one that you're sure is too cold, Then slowly progress one heat range at a time until you find you're not fouling anymore... you seem kinda deep into the build to be working out your first set of plugs right now though, the first test fit should have been with the heads off.
I did not address tip design, but you wouldn't want any extended tip spark plugs, even if you have the clearance to use them without hitting the piston. You may find recessed tip plugs work better for you depending on the turbulence of your exact combustion chambers.
I'm not trying to be a jerk here, but if anything I mentioned is even a little confusing to you... you have a lot of homework to do. Spark plugs are a major part of how racing engines are tuned and a custom build like yours will always involve some amount of trail and error to find the best one for your use. If good enough is all you want, play it safe and eventually you will foul the plugs... if you're out for all the power she can give, you'll be fooling with this stuff forever... weather changes alone may cause you need a different plug.
Sorry, no magic formulas to make this stuff work... but plugs are cheap and as long as you stay conservative, pretty safe to move up or down a step at a time.
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