Plugs Mod

driller

El Presidente
Staff member
I'm not sure who to credit, but I recall seeing a spark plug modification on the 'net and in print which claims to improve combustion, thereby increasing HP/mileage. I recently picked up a set of spark plug wires and decided to replace the Bosch Platinum plugs at the same time I did the wire install. I decided on Autolite 764's.

Basically the mod consists of filing(gasp!) back the ground electrode to midways(or further) of the center electrode. This presumably exposes the spark to the combustion chamber more effectively. The photo below attempts to show the comparison of a typical new plug and after the modification:

http://www.lincolnsclub.org/users/driller/pics/plugmod.jpg

The plug on top has been filed back and rounded off in comparison to a typical plug which overhangs the center electrode completely and is square cut at the end.

A bit of advice here, it is very difficult to file the ground electrode back and round it off without inadvertently hitting the center electrode. My solution was to slide a thin piece if metal between the electrodes to protect the center electrode. I used a paint edger trim tool for this.

After filing I rechecked the gap and set them at 0.048". I applied never-sieze on the plug threads and torqued the plugs to 7 ftlbs. Dielectric grease was used on the plug boots of the new 8.5mm MSD Superconductor spark plug wires(Cobra - # 32219).

http://www.lincolnsclub.org/users/driller/pics/msd8.jpg

Of course the test drive was a lot of fun! :)
 
RE: Plugs Mod

Its not a bad idea to reduce the tip of the anode, but who's to say if it makes any difference? Nippon Denso reduces the tip by angling the sides about 20 degrees to a tip width of about 0.050"......Maybe you're on to something.

I would totally avoid using copper-based anti-sieze lubricant on anything north of the oxygen sensors. Copper will foul them. I would be leary of using graphite-based anti-seize for the same reason, although I don't know if graphite would also foul the O2 sensors.

When I install my plugs, I normally put a single drop of motor oil on the threads. More often than not, I just drag the dipstick across the threads prior to installing them. I've never cross-threaded a spark plug, nor have I ever had one seize up upon removal.
 
RE: Plugs Mod

From MM&FF:
http://www.musclemustangfastfords.com/tech/0207mmff_tech10.jpg
"Rounding off the end of the side electrode as shown here reduces the peak temperature seen by the electrode so moving away from the possibility of detonation from this source. Also, in the relatively swirl-free conditions that exist at low rpm, this form gets the charge burning more effectively. Be sure to cut the electrode so the end of the tip is no further than half way over the center electrode. If plug life is not an issue cut it so it is between a 1/5 and 1/3 of the way over the center electrode."
 
RE: Plugs Mod

JP, I may have to try this again. I tried it several years ago but only roundeded off the corners. I didn't file back the end of the tip.

Thanks, :)
** Bill **
1995 LSC-R'ed w/Recaro's and Cobra R's
Veteran of Carlisle 2000/01/02
[a href=//cardomain.com/member_pages/view_page.pl?page_id=258112]For Pic's and Mods click here[/a]

...Except for ending slavery, fascism, nazism, and communism, WAR HAS NEVER SOLVED ANYTHING...
 
RE: Plugs Mod

I don't believe on a N/A setup you would risk much misfire. Usually a plug misfire is from the gap being too wide from age/wear. Granted, the Autolite 764s may not last 100,000 miles being filed back like this, but most performance minded individuals will replace the plugs long before misfires begin, or at the first sign of a misfire.
 
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