spark plug gap 347?

jcw88

Never played w/ it before so i'm still a virgin!
Mar 20, 2007
53
0
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fernandina, fl
i just thought of something while i was surfing the forums, what is the right spark plug gap for a 347 stoker, p&p victor jr heads, victor jr intake w/ efi spyder power elbow, accufab 80mm tb, 36lbs injectors, msd distributor, 6al box, 255lph fuel pump jumbo rails, hell to much stuff, anyways can somebody give me an ideal? my local performance shop say .055 but seems alittle high:shrug:
 
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Stock gap is .052"-.056"...

It really depends on what compression you are running. Typically the higher compression, the lower the gap needs to be...do you know your compression?

Also, you do have a slightly upgraded igniton over stock with the 6al. That allows a bit larger gap.

Run as much gap as you can without it having a miss at any rpm...
 
imy local performance shop say .055 but seems alittle high:shrug:


Stock gap on the 87-93's is 0.052-0.056"

SO the gap the shop gave you sounds right for an N/A car.

Typically, plug gaps are dependant on ignition. You want to run as BIG as you possibly can before expeirencing misfiring. The reason is the bigger the gap, the larger the spark and the better chance of igniting all of the air/fuel mixture.

The stock ignition is good to a 0.056" gap, with aftermarket components you can sometimes creep it up a bit, but for the most part 0.054" is what most N/A Mustangs run.

You don't really want to make the gap smaller on an N/A car. It's really only done with boosted cars or nitrous because of the spark blowing out over a larger gap.
 
Witch coil are you runing? If its an MSD Blaster series:

.04

If you plan on spraying,drop down to .035-.032

Btw,spark gap will have no effect on performance so long as its not misfiring to begin with,if you have un-burned fuel (witch also would cause lean spots in other parts of the burn) increased plug gap won't solve that. Poor A/F mixture quality, witch has everything to do with the intake to the piston dome/valve reliefs,is responable for that.
 
im gonna be running my car with motor first and tis a 351, and then im gonna go with nitrious, is there any inbetween i can set my plugs at to get the best performance both ways?

The gap for nitrous will run fine on motor,but unless your spraying less than 150hp,that won't matter much as plug gap wont be the issue,heat range will.

The motor n/a will probably like a plug thats one heat range hotter,where as on juice you'll need one thats colder.If your runing 150hp or less,no worries though.