spar plug

If they are older Offenhauser heads, there may not be a direct fit plug available. There was a long discussion on here that came to the conclusion that a spacer will be required on the older Offy heads. Start with this thread : https://www.fordbarn.com/forum/showthread.php?t=272052&highlight=offenhauser.

Also, it's probably not a good idea to get hung up on brand loyalty where spark plugs are concerned. Your "favorite brand" may not have a properly fitting plug available.
 
What tubman said x 2. However, someone said there may be an NKG plug with the proper reach. Worth checking.
 
joe 1950 said:
i always run champion H- 10 in my 50 cpe 26 years and never had a problem with them good luck
Click to expand...

Just about all aftermarket flathead aluminum heads I have ever seen use longer than stock spark plugs (the threaded part). The reason for this is that cast iron is stronger than aluminum which needs more threads to hold the plug. Running stock reach (3/8") plugs in aluminum heads risks stripped threads. It also shrouds the electrode in the plug hole and makes the spark less efficient.

It's not that lots of people haven't done it; I'd say the majority of used heads I have come across have the bottom 2-3 threads all carboned up. It's just not correct. Most use 7/16", 1/2", or even 3/4" reach plugs.
 
Last edited:
i’m going to have to read the article better before putting my two cents worth i didn’t read the part about offy heads sorry about that i’m 74 now and i think i had that same problem in grade school
 
You must log in or register to reply here.
Back
Top