In going through some stuff on a non-chevy project, I came across a box of 5 AC 45 sparkplugs, nearly new. The box said AC 47. The plugs are 14mm so not for a 194. The style and graphics suggest 30s-40s. What have I got here?

Are there 3 thin green rings and 1 wide green ring around the top of the porcelain? Are AC and the number 45 printed in green also?

dtm

Here's what I have: one cardboard box, the size for eight plugs marked AC 47. Inside are five individual AC 47 boxes each with an AC 45 plug. The plugs do not have any bands on the porcelain, but do carry a blue/green AC and 45 on opposite sides of the porcelain.

The 45 fit many models of GM and Non GM vehicles and was superseded by R45 which is still avalable. R is for resistor. It would be a middle heat range plug (the 5 in 45) where the 47 would have been a hotter plug. Lack of green stripes makes it an older version of the 45. I use R45's in my 39, 216.

Dave