Right now i am using the Accel 414s shorty plug gapped at .050. It was at .035 and the engine was running pretty rough, at .050 it smoothed out quite a bit.

Now , my problem is some have said that .050 it too big, even for a MSD ignition (6al) and i need a hotter plug so that i may gap at .035 to gain the same results.
I need to have a very short plug can any body recomend a plug for me?
This is for Brodix Track 1 heads.
Thanks,
Tom

Tom,
Leave your plugs just like they are. The MSD Ignition provides more spark than a conventional ignition system so the plugs can handle the extra gap. Your post mentioned.....

"It was at .035 and the engine was running pretty rough, at .050 it smoothed out quite a bit."

So if it's runnin' better, I say don't bother with a plug change but that's just my opinion. If you decide to change the plugs/gap repost with your results.

The reason i am asking is because on a thread from racingjunk everybody over there is saying that .050 is too big. See below.

http://forums.racingjunk.com/viewtopic.php?t=4716

Tom,
You might want to look here.

www.msdignition.com (http://www.msdignition.com)

They have a tech forum that might give you an answer. If you do find the answer, let us know.

Tom,
I found the literature that came with my 6AL Ignition and on page 6 of a booklet titled "Installation Tech Tips in the section about spark plugs it states

"Carbureted or fuel injected engines can use spark plug gaps up to .050. When an MSD-6 is installed, turbo or supercharged engines will need a smaller gap of .035 because of higher cylinder pressure". This info is from MSD booklet number FRM 10982.

I knew that savin' all of those instructions would pay off one day:D

.050 here with MSD 6al and HEI... no issues.

All right, thanks. Kinda weird to get so different answers from 2 different sites ay?

For normal street cylinder pressures, run .050. If you're blown (supercharged or turbocharged), running a really big shot of nitrous, or really high compression, run .035.

Hope this helps a little.

Running a wider gap increases the workload on your coil. The coil must develop the voltage necessary to jump the gap. Temperature, pressure, and gap are what determines voltage requirements. As you put your foot in the engine you are raising temp and pressure by choice(and desire:)). You are therefore raising voltage requirements. The engine WILL misfire if the voltage required is greater than your coil can supply in the TIME available. As rpm increases, TIME decreases. The coil must do MORE work FASTER. Work generates heat, and when coils(transformers) get too hot they fail prematurely. The only ways you can alter the voltage requirement on your coil is to alter gap or foot position. Also clean plug threads and good wires/connections lowers voltage requirements.

A wider gap can cure an air/fuel mixture induced misfire because it yields a more intense spark and exposes the spark moreso. And for a longer period of time. Pull the plug wire off a lawnmower and hold it 1/32" from ground, then 1/4" and you can see the difference in both time and intensity.

The juice guys say that too big a shot 'puts out the fire' and when it goes out and they put their foot back in it is when bad things happen. This is true because the juice increases cyl pressure, therefore causes voltage requirements to skyrocket. If the coil isn't up to the task it can NOT create the voltage to jump the gap. Cylinders load up with fuel, rpm falls of(TIME increases), the coil can sometimes fire now and uhoh if it does.


Heat range is only applicable to fouling characteristics, and does not determine a plugs firing characteristics. It refers to the length of ceramic insulation they put on the center electrode to alter how hot the metal stays. Not how hot it fires. In extreme cases a hot plug can cause pre-ignition by becoming a hotspot in the cylinder though.

I keep a spare new coil :).