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Author Topic: Spark plug gapping  (Read 3713 times)

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Nicks92jeeper

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Spark plug gapping
« on: November 19, 2011, 03:27:47 AM »
So I have the MSD ignition coil for my Jeep and that runs at 40,000 volts, stock distributor cap and rotor and double platinum I think iridium plugs. Anything better for plugs or the setup I have? What gapping on the plugs could I get away with? I think they are set at the recommended gapping. Is gapping plugs more about experimenting with what your engine likes? Will better wires give me much of an improvement.

Anything else I need to consider?
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YJmechanic

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Re: Spark plug gapping
« Reply #1 on: November 19, 2011, 08:13:16 AM »
the wires are one of the most important parts.  doesnt matter what the coil is if the wires are too high resistance to make use of it.  you need good set of low resistance wires and then id say go ahead and start playing around with the gap a little.  just dont go to far with the gap or youll start missfiring from the spark not being strong enough to make the gap.
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Nicks92jeeper

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Re: Spark plug gapping
« Reply #2 on: November 19, 2011, 12:04:40 PM »
For wires then. what size would you recommend?
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Nicks92jeeper

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Re: Spark plug gapping
« Reply #3 on: November 19, 2011, 12:43:47 PM »
I also have the MSD ignition coil at 40,000 volts. Should I be looking at something better than that coil?
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YJmechanic

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Re: Spark plug gapping
« Reply #4 on: November 19, 2011, 07:04:18 PM »
No that coil is fine, just get some performance wires that are 8mm or Higher  and are made well
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Offline FourbangerYJ

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Re: Spark plug gapping
« Reply #5 on: November 19, 2011, 08:08:32 PM »
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Scott~

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Nicks92jeeper

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Re: Spark plug gapping
« Reply #6 on: November 20, 2011, 01:45:33 AM »
Those wires shure are purdy!!! Thanks for the link and the info. Out of curiosity, does anyone know how many volts the screamin demon coil puts out. I got a 40,000 on my MSD coil and was wondering the difference. I already have 8mm wire but they are just autolites and not really for performance.

I figured with the intake mods and swapping out the injectores with the ones that came out of the Lincoln Town car that this would just about be as fine tuned as I can go without spending serious cash.

With a bored out 4.0 TB, cold air intake system, openened up opening on the intake manifold, P and P, injector swap and ignition coil, what would be a safe estimate that gapping the plugs and adding performance wires would get me. Am I looking at 1 or 2 miles per gallon better and a bit better HP or am I looking at less? Will it be worth the money for performance or just smiles per mile.  My Jeep already sounds like my dads F250 and any more I fear the cops will be called for disturbing the peace!
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Offline sharpxmen

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Re: Spark plug gapping
« Reply #7 on: November 20, 2011, 08:22:32 AM »
Quote from: Nicks92jeeper on November 20, 2011, 01:45:33 AM
Those wires shure are purdy!!! Thanks for the link and the info. Out of curiosity, does anyone know how many volts the screamin demon coil puts out. I got a 40,000 on my MSD coil and was wondering the difference. I already have 8mm wire but they are just autolites and not really for performance.

I figured with the intake mods and swapping out the injectores with the ones that came out of the Lincoln Town car that this would just about be as fine tuned as I can go without spending serious cash.

With a bored out 4.0 TB, cold air intake system, openened up opening on the intake manifold, P and P, injector swap and ignition coil, what would be a safe estimate that gapping the plugs and adding performance wires would get me. Am I looking at 1 or 2 miles per gallon better and a bit better HP or am I looking at less? Will it be worth the money for performance or just smiles per mile.  My Jeep already sounds like my dads F250 and any more I fear the cops will be called for disturbing the peace!


if you get 5% more air compared to before and you added 5% more fuel you're lookint at 5% more HP - so that would be 6HP for the 2.5L. all guessing game unless you do some AFR monitoring/logging at wot before and after the changes or some dyno time.
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Offline FourbangerYJ

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Re: Spark plug gapping
« Reply #8 on: November 20, 2011, 09:39:39 AM »
They don't list the volts on their web site. But the wires are 10mm.
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Scott~

Using tools you have not used in a while is like shaking hands with old friends. :nod:

Nicks92jeeper

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Re: Spark plug gapping
« Reply #9 on: November 20, 2011, 04:59:49 PM »
5% is still better then what I had before!
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Offline sharpxmen

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Re: Spark plug gapping
« Reply #10 on: November 20, 2011, 08:13:00 PM »
Quote from: Nicks92jeeper on November 20, 2011, 04:59:49 PM
5% is still better then what I had before!

that was an example, but if your injectors have 5% more flow it is a good guestimate
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'95 YJ, NSG370 6spd / Hurst shifter, Dana 300 + 4:1 Doubler / tri-stick, Custom skid, Super D35 / Auburn LSD / 4.88, 35x12.5x15 BFG KM2, 64mm t/b, 1.7 RollerRockers, MkVIII e-fan, Dual Diaph Booster
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Offline dwtaylorpdx

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Re: Spark plug gapping
« Reply #11 on: November 20, 2011, 09:29:32 PM »
You only need the voltage higher if the compression of the engine is higher.

At anything under 12 or 14 : 1 40K will do the job fine.
Spend your money on better injectors before a better coil.
If you go too high on the voltage it can start arcing to the piston
Or the head and do bad things (TM)

Dave

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Nicks92jeeper

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Re: Spark plug gapping
« Reply #12 on: November 21, 2011, 01:59:55 AM »
About 2 months ago I went with the #19 stock mustang injectors. Well I got them out of a Lincoln Town car. I like the response I got from those and helped the engine come alive. At this pont I do not want to mess around with fuel pressure. This summer I had to fix the head gasket and had to have the head plained down a bit so that created a bit of difference and the engine had a bit more pep. With all the upgrades I have on the engine primarily on air and exhaust flow and the MSD ignition coil I have, I just wanted to have all the benefits I can have. In the next week I will be getting some performance wires and then start gapping to see what happens.

Thanks for all the info everyone.
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Offline sharpxmen

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Re: Spark plug gapping
« Reply #13 on: November 21, 2011, 09:13:44 AM »
Quote from: Nicks92jeeper on November 21, 2011, 01:59:55 AM
About 2 months ago I went with the #19 stock mustang injectors. Well I got them out of a Lincoln Town car. I like the response I got from those and helped the engine come alive. At this pont I do not want to mess around with fuel pressure. This summer I had to fix the head gasket and had to have the head plained down a bit so that created a bit of difference and the engine had a bit more pep. With all the upgrades I have on the engine primarily on air and exhaust flow and the MSD ignition coil I have, I just wanted to have all the benefits I can have. In the next week I will be getting some performance wires and then start gapping to see what happens.

Thanks for all the info everyone.

Ford 19# flow slightly less than the stock ones (by 0.1 lbs/hr so it's negligible) but probably compared to your old ones these would flow and atomize better, i would say you brought your engine back to stock specs with no or minimal power increase. You'd get better power output with about 5psi increase in fuel pressure (I wouldn't go higher than that).
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'95 YJ, NSG370 6spd / Hurst shifter, Dana 300 + 4:1 Doubler / tri-stick, Custom skid, Super D35 / Auburn LSD / 4.88, 35x12.5x15 BFG KM2, 64mm t/b, 1.7 RollerRockers, MkVIII e-fan, Dual Diaph Booster
Latest: Corbeau BajaRS heated seats :dance: keeping warm the rear end

Nicks92jeeper

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Re: Spark plug gapping
« Reply #14 on: November 21, 2011, 03:51:26 PM »
I knew that they were slightly less for # but after the install it felt better. I liked the noise it made and it just all around ran better. Then I seafoamed the crap out of the system which pry did nothing but cost me $8.00 but I felt better about it!! Pry no power gains if minimal at best , like you said.

With the fuel pressure, for a guy who doesn't have a machine shop, what would be a good option (For fuel pressure regulators) for that? I thought I read that there were a few you could swap in from other vehicles so as to not spend hundreds of dollars but I am not sure. Then again with my Jeep I am in a location with really no serious trail (IOWA) and no serious crawlin so power output is not a serious thing on my mind but is nice. I also use my jeep as a daily driver so the route I have been going for is to increase fuel efficiency as well as HP, compared to just HP and torque. Right now where I live, I could race any 2.5L Jeep and I know I could win! Which the last sentence really does go against what I am aiming for.  :nono:
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