I"ve been trying to find an answer to this question myself and belive the Autolite 3924 corresponds to the Champion RC12YC.
24-7423 - Champion RC12YC Spark Plug
RC12YC Champion Replaces Autolite 3924, NGK BCPR6ES..
I have autolite sparks plugs ARF32M and need to know the cross reference to NGK
64 Autolite Replaces Champion RN11YC, NGK BPR5ES
Autolite 217.
308
Champion RA8HC has the same thread, seat, reach, hex size, and terminal type. I ordered a Kohler plug from Amazon and they actually shipped me this Champion Plug.
NO.
Most all brand spark plug brands are on the cross reference including Champion. Some of the brands that cross reference to Champion are Autolite and Denso,
Champion CJ7Y Champion RCJ6Y Autolite 2974 Bosch WSR6F Denso W22MP-U NGK BPMR7A
Yes, it's the Holley 1940. You can get them from Champion Carburetor.
Champion 5861 or Autolite 458.
0.32 with Bosch, Ngk , Champion , Autolite 0.28 with Denso
champion #940