AC Spark Plug Numbering System Chart and Spark Plug Question

[Riviera63]

I ran across this while researching spark plugs. It was very helpful to me to make sense of the numbering system for the AC spark plugs and I thought it might be helpful to others. I do have one question about the AC spark plugs for my 63 401. Are there any other designations in the R44 series of plugs that will work adequately besides the R44S in the 401? For example, the R44SX is designated wide gap for H.E.I. Can one just simply regap these plugs to the correct gap and use them or is there something else fundamentally different that will make these unusable? Any input is appreciated. Thanks.

 

Bill

 

 

 

 

[EmTee]

The wide gap 'X' plugs use a physically longer ground electrode, so if you try gapping them to 035, the ground electrode will not be parallel to the center electrode.  Only the tip of the electrode would be at the desired gap and the gap would quickly widen as the tip of the ground electrode erodes.