W9 plugs

[henryv11]

Could someone please tell me the correct plug to use for a 1948 W9. Champion if avaliable.
Thank you

 

[Andrew Z]

D18Y or D21's work well

Andrew

 

[glennster]

i dont think they will work. my w-9 takes a bigger plug, the d-18 or autolite 386 for the m are too small for the spark plug hole. i dont remember the number right off hand, i'd have to look and see what they are.

 

[Owen Aaland]

The original heads used plugs with 7/8 inch threads. Later heads use 18 mm thread plugs.