Waxing intellectual on plug gapping?

lendaddy · 06-25-2003, 09:13 AM

I fouled a plug this morning! I havn't pulled them yet but I am 90% sure thats what it is as I have done it before. I have an MSD 6AL so last year I took the advice of Steve Werner(Rennlist) and gapped to .042". Well I fouled 3 plugs right away. Then When I had my motor out I set them to .037" thinking that would be safe. Well no, fouled this morning. (they did not appear oily the first time, we'll see on these) anyway the factory gap is I believe .024" and I am considering going .027" or so. Here is the dilema, I was told a long time ago that running too tight a plug gap can burn a piston as the spark is so hot when it is short. If this is true, will it be a problem to run the standardish gap with my "much hotter" MSD setup? And to add to the mix I am using a Bosch blue coil, now isn't that what determines the actual spark strength, meaning I am not really any hotter? And if so shouldn't I run a standard gap or is the blue coil also high voltage? This is getting really muddled but I think you can get my ?'s Maybe Steve Werner uses the MSD coil, I will have to check. So, bottom line, where would you gap my plugs and why? Thanks. Oh yea NGKBP8ES plugs, screw the platinums they never did anything for me(platinums are in it now)

cstreit · cstreit's Garage

That's a pretty cold plug! You might try a slightly hotter plug and .035 gap to prevent fouling. WOrked on my setup. I doubt that you'll get a spark so hot as too burn a piston during street use...

Rot 911 · 06-25-2003, 09:35 AM

I'm with Chris on this one and remember with NGK's the lower the number the hotter the plug so go with BPR7ES. I would start my gap at .030 and if there is no fouling then open it up a bit.

lendaddy · 06-25-2003, 09:38 AM

Even the stock replacement is the "8" equivelent, and I am somewhat modded from stock so I would be afraid to go hotter. I see now that Steve Werner does not like the blue coil I have so I will change that as well. I think I will go with .030 unless someone tells me that would be bad. Thanks.

GMR911 · 06-25-2003, 07:43 PM

Just a quick question. Does a narrower gap or a wider gap prevent fouling? Thanks Jerry

Doug Zielke · 06-25-2003, 07:56 PM

No, no, no!
A smaller spark gap will *not* "burn pistons".
That sounds like the birth of another stupid myth.

If you are fouling plugs (and a NGK "8" is quite cold) go a step or two hotter. Keep an eye on the plug color and condition of the insulator tip. You don't want too go too far (too hot) in the other direction.

Zendalar · 06-25-2003, 09:12 PM

Heh, i am running too hot plugs then i would think, but these work better than 6 or 7. I run with NGKBP5ES.

greglepore · 06-26-2003, 04:09 AM

I'd try the MSD coil with the 6al. Back in my 914 w/carbs days, using the MSD allowed a larger gap, and the car was more tolerant of a slightly rich mixture. I was warned against the blue coil with the MSD, don't remember why. The coil controls the spark intensity, the MSD just the rate.