What plugs and gaps are you guys running with superchargers and MSD ignitions? I have just installed an MSD 6AL ignition on my TPI 350 with Paxton sn 2000, and still have my plugs gapped at .035". The MSD instructions say to raise the gap to .050-.060, but should I try something different for a blown application? Thanks for any help.

 

my gap is at .35 ang get some colder sparkplugs too.

 

I'am pretty sure mine are at .040" but maybe at .045", no problems so far.

 

Thanks for the info. Antoine, are you using the Paxton supplied air filter on your set-up? I hate the one that came with the kit. It seems way too small and probably quiets the whining sound down being it is made of paper. I would like to hear it whine a bit, and am thinking of going to a large K&N type filter. Any thoughts on this?

 

I've got mine gapped to .035 now with the Accel 300+. Before w/ the stock HEI the spark was getting blown out at 3k rpms @ .045 gap (but 17 psi), and then re-gapped down to .035 & made it up to 3800 rpms.

 

i put a k&n filter on it because paxton sends with the kit was a paper filter and they wanted 50 dollars for it put a k&n on it 3inch inlet.also i use ngk sparkplugs.

 

Due to the superchagers heat you will want to decrease the gap from manufacturers spec to reduse detonation. The specs just above stock are a great place to start. Youll also want to take the advice given above and use colder plugs. What you want to do is try different gaps for a few thousand miles and when you get the best fuel economy youll also be making the most power.

 

The plug gap has nothing to do with detonation. It's strictly the ability of the ignition system to generate a spark. If the gap is too large, you'll get a misfire (not detonation) since the mixture isn't ignited. Increasing the cylinder pressure (with boost or compression) creates a larger resistance in the air gap between the plug electrode and ground strap. Increasing resistance (with pressure or gap) increases the voltage required to generate a spark. When you don't have enough voltage, you don't get a reliable spark (i.e. me, at 3800 rpms on the stock HEI, .034 gap, and 17 psi) and get a misfire. You can close the gap, increase voltage (aftermarket ignition), or lower cylinder pressure to get the spark.

I just wanted to clear that up.

A.

 

I run mine gap a .030 with 14lbs of boost

 

Air is an insulator, the denser the air gets the more power you need to jump the same gap, so you “gap down” to keep it something that you can fire across.

I’ve messed with cars that have had to run gaps as small as in the low .02x” range to consistently fire at high rpms, but at that point you start getting misses at idle.

FWIW, gap does have something to do with detonation, but not what you expect. As the gap gets smaller the plug runs hotter and is more prone to becoming a source for preignition.

 

Thanks for the correction. This begs a question - why?