I have a '98 Jeep Grand Cherokee Laredo I6 with an OEM specified plug gap of .035. I've had an Accel super coil installed and Magnecor wires for the past couple of years. Bosch Super plugs gapped to .040. It was recommended to me to increase the gap by .005 with the Accel coil mainly for better throttle response so that's why I did that. Have 30K on curent plugs so I bought a new set of Champion Truck plugs. I was thinking of just going with the OEM gap of .035. Would this be ok even though I have the Accel coil? I still have the stock coil in the garage. Thanks.
Spark plug gap +.005
- Thread starter jeepzj
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.005 isn't really going to make that much of a difference...you'll be good to go with whatever you choose to do.I install the Champion Gold Truck plugs #4412 in both my Jeep's 4.0's,the XJ at .035 and the TJ at .040...no difference...the centre electrode on the Gold Champs are larger than the stock plugs..they say this increases performance...can't tell...they ran great with the stock plugs as well.Good thing is that changing plugs on the Jeep motors is a breeze
bye the way the Gold Truck plugs come gapped at .040 out of the box.
running the largest gap you can get smoothes the motor and adds gas mileage.
It was a trick mopar used to smooth the idle on the slant six...upped gap from 35 to 50. I have a capacitive discharge setup with spiral core wires and run my gaps at 60 on my slant six...
Dan
It was a trick mopar used to smooth the idle on the slant six...upped gap from 35 to 50. I have a capacitive discharge setup with spiral core wires and run my gaps at 60 on my slant six...
Dan
True but can I use the Accel coil, which provides more spark to the plugs compared the the stock coil, be ok with a .035 gap instead of .040? Will it hurt anything? Will it cause premature wear on the plugs? Thanks.
MolaKule
Staff member
The closer gap results in more current through the coil with a subsequent temp rise. With the higher voltage Accel coil, I'd go with 0.040 or slightly higher.
Jeepzj, the Accel is an excellent coil. They have an internal resistor to limit current flow, so they're safe to run anyway you want. I'd agree with Molekule and up the gap to about .044", especially with the Magnacore wires.
When I replaced my 4.0 wires with solid cores, a huge misfire problem occured. It was caused by feedback/'flyback' into the ignition module. I solved it by using a resistor wire on the coil secondary. This gives me an effective 5K ohms through the plug wires. I mention this because the Magnacores are spiral wrapped solid cores, and have very low resistance. It might be a good idea to check one with an ohmmeter to make sure the resistance isn't too low. Anything above 2K-3K ohms should be OK.
When I replaced my 4.0 wires with solid cores, a huge misfire problem occured. It was caused by feedback/'flyback' into the ignition module. I solved it by using a resistor wire on the coil secondary. This gives me an effective 5K ohms through the plug wires. I mention this because the Magnacores are spiral wrapped solid cores, and have very low resistance. It might be a good idea to check one with an ohmmeter to make sure the resistance isn't too low. Anything above 2K-3K ohms should be OK.
The ouput of an ignition coil is current limited by the resistance of the secondary winding and plug wires.. Decreasing the plug gap will not materially increase the current through the plug.
A larger gap, however , requires a higher voltage to fire. Carried to an extreme (very large gap) the voltage requirement could become so high as to stress the insulation within the coil itself and cause premature coil failure.(That High voltage really wants to spark somewhere) An open in the high voltage circuit is much more serious than a direct short as far as damage to the ignition components are concerned. If your the kind of person that changes plugs frequently, then by all means go with the larger .04 gap. If your going to leave the plugs alone for 50,000 miles your probably better off sticking with .035. They will widen to .04 by themselves.
Ed
A larger gap, however , requires a higher voltage to fire. Carried to an extreme (very large gap) the voltage requirement could become so high as to stress the insulation within the coil itself and cause premature coil failure.(That High voltage really wants to spark somewhere) An open in the high voltage circuit is much more serious than a direct short as far as damage to the ignition components are concerned. If your the kind of person that changes plugs frequently, then by all means go with the larger .04 gap. If your going to leave the plugs alone for 50,000 miles your probably better off sticking with .035. They will widen to .04 by themselves.
Ed
when they tell you to gap at a specific gap when (re)installing plugs, they're counting on that gap growing over the service life of the plug. So if you want to go a little over, that should be fine: just pull them every, say, 10k and check & regap.
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