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1969 Nova SS502
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I am a little confused and hope you guys can give me some info. I installed some Autolite 3932 in my new 502 that is running AFR 305 heads. I used these plugs because that was what AFR recommended. I have 3 questions:
1. The plug I am running is a race plug with a very short tip which does not reach the center of the electrode. I checked the gap on the plugs out of the box and they are around 25,,,,very small gap. I attempted to change the gap but due to the very short tip and distance between the tip and electrode I was unable to find a tool to change the gap.
2. I am also running a MSD system and they recommend that the gap be around 50 for a starting point.
3. What is the effect on you motor if the gap is not correct and in my case not enough gap.
The car runs and starts fine but I am afraid I am missing out on either power or correct burn.
 

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redride said:
I am a little confused and hope you guys can give me some info. I installed some Autolite 3932 in my new 502 that is running AFR 305 heads. I used these plugs because that was what AFR recommended. I have 3 questions:
1. The plug I am running is a race plug with a very short tip which does not reach the center of the electrode. I checked the gap on the plugs out of the box and they are around 25,,,,very small gap. I attempted to change the gap but due to the very short tip and distance between the tip and electrode I was unable to find a tool to change the gap.
2. I am also running a MSD system and they recommend that the gap be around 50 for a starting point.
3. What is the effect on you motor if the gap is not correct and in my case not enough gap.
The car runs and starts fine but I am afraid I am missing out on either power or correct burn.
The car will miss. It may run rich. It may backfire.

A longer spark will lead to more complete combustion at the proper time.
 

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redride said:
I installed some Autolite 3932 in my new 502 *snip* because that was what AFR recommended. I have 3 questions:
1. The plug I am running is a race plug with a very short tip which does not reach the center of the electrode. I checked the gap on the plugs out of the box and they are around 25,,,,very small gap. I attempted to change the gap but due to the very short tip and distance between the tip and electrode I was unable to find a tool to change the gap.
2. I am also running a MSD system and they recommend that the gap be around 50 for a starting point.
3. What is the effect on you motor if the gap is not correct and in my case not enough gap.
The car runs and starts fine but I am afraid I am missing out on either power or correct burn.
Re #1. AFR is erring on the safe side- you could use those plugs w/almost any set-up, and the plugs would not be the cause of detonation- they're cold, close gapped, and a race-type plug. No adjusting the gap is usually done w/these AFAIK.

Re #2. If available where you get parts, NGK FR45 or a cooler FR4 (lower numbers = colder w/NGK's) or it interchanges w/a RC12YC- which I personally have absolutely NO problem with- despite all the p-nut gallery talk of how Champ plugs are N/G :rolleyes: . It has a projected tip and 0.060" gap out of the box, IIRC- so is close to what you need. I've used these in Edelbrock BBC heads in the past. Be sure to check the clearance w/any projected tip plug.

This is from hand written notes, so please verify it (and all else, for that matter) before using:
RC12YC crosses over to an AC FR1LS, or a FR3LS depending on heat range wanted- or Rapid Fire's #5
(originally used in a GM Quad 4).

Re #3. At idle, there may be a tendency to some misfiring due to the lean, less turbulent mixture- this is where you'd like a big, hot spit of juice across the electrodes to get the charge lit off.

A close gap doesn't require as much current to bridge the gap, so there's less "hit" to the spark than if it was wider. A narrow gap will, however, provide a spark in situations where a wide gap could not- like boosted, nitrous, high compression, turbo, etc. This gets back to AFR erring on the side of safety, IMO. With their recommended plugs, you'd be fairly safe no matter what- at least for long enough to make changes if colder was needed, before terminal damage was done.

I suspect that in the end, you'll end up somewhere around 0.045" gap, maybe a bit more for the best all-around performance.
 
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