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Plug gapping and Pertronix

Swaayze

Jr. Member
Joined
Oct 9, 2003
Messages
136
Loc.
DFW, TX
Got a hard starting and somewhat poor running 302 (1973). I suspect a carb rebuid is in order but I haven't checked fuel pressure yet and I figured new plugs and points wouldn't hurt regardless. Much to my joy when I pulled the cap I found a Pertronix (coupled with an Accel SuperCoil). My Haynes manual shows the correct gap for a '73 302 to be 0.035, but I pulled one plug to examine and found 0.045 (which, strangely, is the correct gap for the same plug on a '74).

My questions: does the gap change with a Pertronix or were my plugs just gapped incorrectly by whomever installed them? Why would the exact same plug have a significantly different gap target on a '74 (that was still a point distributor wasn't it)?


Thanks
 

broncnaz

Bronco Guru
Joined
May 22, 2003
Messages
24,341
Some 74's had points but the bigger gap is for electronic the same plugs were used until about 77 then they changed to smaller plugs. .045 is correct for electronic ignition and you might be able to open it up .005 -.010 more for some added spark power but you have to really watch it because you can open to far and negate any gain and over work the coil.
 

thegreatjustino

Contributor
Red Head Grease Monkey
Joined
Jan 23, 2002
Messages
15,624
Loc.
Stockton, CA
I overgapped the plugs when I installed the pertronix igniter and coil in my Bronco. With the more powerful coil you can get away with the bigger gap.
 

70 sport WA

Sr. Member
Joined
Nov 1, 2003
Messages
768
To clarify responses to the OP, apparently an electronic-type ignition needs a bigger gap than with stock points (.035)?

In other words, the gap needs to be closer to .045?
 

broncnaz

Bronco Guru
Joined
May 22, 2003
Messages
24,341
Yes the electronic systems can handle the bigger gap. Where points systems cant you end up burning the points up quicker with too large a plug gap
 
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