View Full Version : spark plugs for a dual carb flathead six

09-23-2005, 12:59 AM
I don't know much yet about spark plugs, so I hope someone can help educate me. First, thanks to N8N for his parts interchange document (I guess I should give the link here, hope Nate does not mind: http://home.comcast.net/~njnagel/files/interchange.pdf ).

I noticed in the parts manual for the 2R and E series trucks with a Champion Six motor, there are two plugs listed: Champion's J7 & J8.

Which of these would be better to use after I put on a dual Offenhauser intake with two Carter WE carburetors, and why? Or, is there yet a different plug that would be best for this situation?
Keeping in mind the need for a short nosed spark plug in the flathead six motor.

Thanks in advance,

1955 1/2 Ton Pickup

09-23-2005, 01:23 AM

Back in high school, when I drove a Champion, I used lawn mower spark plugs made by the Auburn Spark Plug company. My father was in the lawn mower business, and got these wholesale by the case. And they worked just fine, too.

This was mostly before the time of the small-size plugs currently seen in small engines. Those plugs were roughly equivalent to a J8 Champion.

You can find charts to "read" spark plugs in many automotive service books. You look at the color and nature of the deposits on a used plug to determine if it has been running too hot or too cold, and then adjust the heat range of the next set of plugs accordingly. That way, you select plugs that are best suited to YOUR engine and YOUR driving habits.

I'd start with a set of J7s, read them, and proceed accordingly.

Gord Richmond, within Weasel range of the Alberta Badlands

09-23-2005, 07:32 PM
I agree with Gord's advice; also keep in mind that a J-7 and J-8 are pretty much the same plug, the only difference is the heat range. The J-8 is a little bit hotter than the J-7, so if you have a fouling issue with the J-7 you might want to try a set of J-8s.

I believe Champion, AC, and Bosch all use a numbering system where the higher number is a hotter plug.


55 Commander Starlight
62 Daytona hardtop