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Brian G. Ahart

Spark Plug Reference Matrix

  Plug Type AC Champion NGK Autolite Bosch
B, C, CA, WC, WD Non-Resistor (Magneto) 45 J8 B6s 295 W8E
U, A Non-Resistor (Magneto) C75 W14   3075  
WD, WD45, D10-D17 Resistor (Distributor) R45 RJ8C BR6s 303 or 295 WR9EC

NOTE: Non-Resistor plugs can be used with distributor ignition, but Resistor plugs should not be used with magneto ignition.

AC Spark Plug Numbering System
Champion Spark Plug Numbering System (jpg, 126k)
NGK Spark Plug Numbering System (pdf, 174k)
Autolite Spark Plug Numbering System (pdf, 16k)
Bosch Spark Plug Numbering System (pdf, 2061k)

Spark Plug Cross Reference Spreadsheet (xls, 1704k)
Spark Plug Cross Reference