Green markings on AC spark plugs

[Jeffrey S.]

Re: Green markings on AC spark plugs

Clem:
I believe that the ribs were added also to give a better seal for the boot to help keep moisture out and to better hold the boot on. In a running change in Marh of '57 due to complaints of the AC44's cold fouling, the old smooth porcelain 46-5's were installed but had to be removed from production soon after because the boots would not hold on the plugs. The then new style AC46's were use which had the ribs and were 2 heat ranges hotter to prevent the fouling.
Jeff

[Troy P.]

Re: Green markings on AC spark plugs

Interesting that they kept making the smooth plugs once they'd come up with a better design with the ribs.

So it would seem we are concluding the numbers we think are dates on the boxes really are dates. Anyone disagree?