spark plug gap question

[jerry S]

Is there a general rule on determining the best gap for your plugs? I know I have the correct plugs for my CR (10.5:1) but am ignorant as to the optimal gap. Can somebody who knows give me some tips?

 

[iskwezm]

depends if you have a stock ignition or add on box.Mine used to be at .035 for the nitrous,but i have since closed the gap to .028 for the blower

 

[2nd Mustang]

I have a 302 with 10.5 to 1 compression, mild hydraulic cam, headers, Holley 600, MSD6A, Unilite electronic ignition conversion, etc...... I have my plugs set at .045. It seems to run okay, but then I haven't really looked at them in over 3 years.

 

[jerry S]

depends if you have a stock ignition or add on box.Mine used to be at .035 for the nitrous,but i have since closed the gap to .028 for the blower

I have an aftermarket ignition: MSD 6AL with the Pro-Billet distributor.

 

[D.Hearne]

I have a 302 with 10.5 to 1 compression, mild hydraulic cam, headers, Holley 600, MSD6A, Unilite electronic ignition conversion, etc...... I have my plugs set at .045. It seems to run okay, but then I haven't really looked at them in over 3 years.

Ditto on mine with electronic ignition-- .045. Works fine. Plugs last well over a year.

 

[Pbum5]

Also have a Unlite and gap at .045 with good results

 

[jerry S]

thanks for the replies. What I am wondering is whether there are any criteria for determining the correct gap or is it just trial and error?

 

[D.Hearne]

I just go by what the factory settings are, points gap was around .035, electronic is usually .040-.050. It also depends on how hot a coil you run. Wider gap takes more voltage to get the spark.

 

[jerry S]

I just go by what the factory settings are, points gap was around .035, electronic is usually .040-.050. It also depends on how hot a coil you run. Wider gap takes more voltage to get the spark.

I should have specified that I have an MSD Blaster 3 coil to go with my MSD HEI distrib and MSD 6AL box. This particular coil puts out 45,000 volts max. Is it a safe bet to split the difference between .040-.050 and gap the plugs at .045 as suggested in this thread?

 

[D.Hearne]

I should have specified that I have an MSD Blaster 3 coil to go with my MSD HEI distrib and MSD 6AL box. This particular coil puts out 45,000 volts max. Is it a safe bet to split the difference between .040-.050 and gap the plugs at .045 as suggested in this thread?

With all that firepower, those plugs should fire even with double that The first time I tuned up my 95 E150's 351, I checked the plug gap on the originals as I pulled them. After 80,000 miles, they still fired fine, I just figured it was time. The gap on most was something like .085 But all in all .045 is a good start.

 

[jerry S]

Thanks everyone. I appreciate the help.:SNSign: