Have a problem...I am looking to replace the spark plugs on a 1963 Chrysler Newport for a friend. Owners manual lists Champion RJ12YC as the number...Every parts place I call says the number is RJ14YC. Called Champion and they said those 2 numbers are not interchangeable. Now I go to order the ones the owners manual calls for and am told those spark plugs are for small and marine engines....help! Anyone know anything about this and can offer help.

 

What fricken in motor do you have??
Post a quastain with very little info. , good luck.

 

383 or 413? It maybe the same plug but let us know!

 

Difference is the heat range. so I would use the 12's

 

I thought the 12 was discontinued?