plug gap
Thread Starter
Safety Car
Joined: May 2003
Posts: 4,283
Likes: 0
From: Houston Texas
plug gap
I tried finding as much info before asking this. I have msd 6al btm, msd blaster replacement coil and msd 8.5 wires but what plug and what gap. Autolite 104's, Ngk's but what gap, stock or narrower? 6psi blower with upgraded exhaust. Thanks for suggestions!!!
Le Mans Master
Joined: Apr 2000
Posts: 6,294
Likes: 0
From: Amateur driver on open course.
Re: plug gap (vvv90)
I would think MSD would be able to recommend something for your application wouldn't they? :skep:
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Melting Slicks
Joined: May 2000
Posts: 2,148
Likes: 1
From: Chandler AZ
Re: plug gap (BAM92)
For plugs you want a basic sturdy plug, 2 heat ranges colder than stock. I'd suggest Champion or Autolite truck plugs; Delco rapidfires seem to be very popular also. I've been running NGK V-power race plugs but the electrodes seem to wear faster.
As for gap, run the largest you can without misfiring under load. What determines the limit is cylinder pressure / density, and the voltage you deliver to the plugs to make it jump the gap. Voltage to the plugs depends on primary voltage out of the ignition box, coil step-up ratio, and good quality wires. Once the spark jumps, a high current coil will give a nice fat plasma discharge around the electrode to set off the flame front. Plus your multiple sparks don't hurt either (below 3000rpm).
Sounds like you have a decent ignition system there that should handle .045" just fine. I've run .055" at 10psi with the same MSD box, wires, with a higher voltage 53kV coil.
As for gap, run the largest you can without misfiring under load. What determines the limit is cylinder pressure / density, and the voltage you deliver to the plugs to make it jump the gap. Voltage to the plugs depends on primary voltage out of the ignition box, coil step-up ratio, and good quality wires. Once the spark jumps, a high current coil will give a nice fat plasma discharge around the electrode to set off the flame front. Plus your multiple sparks don't hurt either (below 3000rpm).
Sounds like you have a decent ignition system there that should handle .045" just fine. I've run .055" at 10psi with the same MSD box, wires, with a higher voltage 53kV coil.
