91b1 spark plug

[Eric Haynie]

What plug should i be useing. It burns gas.
Eric

[Jeff Campbell]

the factory stock plug was a Champion L78, if you can't find one look for a cross to another brand/type. I have used the Autolite 411 plug in Macs (that have 1/2" reach heads, remember some older motors have heads that use 3/8" reach plugs), it's a good all around plug for 91 / 101 motors on gas or methanol.

Jeff

[Eric Haynie]

older 91b1's or just mac's in general?

[Jerry VanDeusen Jr]

i have been running the 411's in my b1's on gas no problems
plus you can get them at your local parts house kragens, napa

jerry

[Eric Haynie]

okay I got a champion l78c's from the parts store the c stands for copper.
Did not have just a L78 or a autolite 411
Crossed the champion plug to a NGK B7HS
so I bought the one champ. plug they had and got 2 NGK's
What should I gap them at?

[Rob Voska]

.025 - .030 I use my thumb nail.

[Ernie Fisher]

Hmmmmm----Wonder what Uncle Denver would use

[Jeff Campbell]

... do check your plug after running the kart to make sure the plug isn't too hot. The B7HS might be too hot a plug, its probably closer to a Champion L82 (which was supplied by the factory as a break-in plug, that they test started the motors with, an L78 was normally included in the bag of stuff with the motor). There are conflicting cross reference charts out there, I can see charts that have a L78C plug crossed to an B7HS, B8HS, B9HS, and B10HS !!! I have run the B8S (the 3/8" reach version) in my older motors, like my MC20's, it is a good match. Generally I have found it easy to find Nippendenso W24FS-U, NGK B8HS, and Autolite 411 plugs, they should all work, but always check your plug after running a short session on the track.

Jeff