Before this information is lost to father time I thought it might be informative to display the differences in the original Champion spark plugs installed in the old original ignition engines.
The Champion V was the first plug offered in the first ignition engines, such as the Brown Jr. The plug had 3/8”-24 thread size plug base. The center electrode came out to a fine point. The ground (loop) terminal was .0405 dia. Wrench size 1/2”.
The Champion V-1 came out in later production with a slightly larger center electrode ending in a flat tip. The ground (loop) terminal was also larger at .0415 dia. The V and the V-1 can be used interchangeably.
The Champion V-2 is a smaller plug, introduced with the later smaller displacement engines. The plug has a 1/4”-32 thread size base with a 7/32” thread depth. The center electrode came out to a fine point with the standard (Loop) shaped ground. Wrench size 3/8”.
The Champion VR-2 was used in the high performance engines such as the McCoy, Dooling and several others. The VR-2 uses the same metal base as the V-2 with 1/4”-32 thread size. The porcelain insulator is taller than the V-2. The center electrode was more recessed, ending in a flat tip. The ground electrode was flat (not looped) to allow clearance for the lesser head to piston clearance on these high compression engines. Wrench size 3/8”.
The Champion V-3 was the smallest size plug using a smaller base, but still utilizing the 1/4”-32 thread size with a shorter 1/8” thread depth. Wrench size 5/16”.
By Charlie Reich, October 2010