Re: [Amc-list] 4.0 Spark plugs.

["John Elle" <johnelle@xxxxxxxxx>]

Snip
have a quick question: Does anyone have a part number for spark plugs
one heat range hotter than stock for a 4.0 head?  I'm running a 4.0
head on a 4.2 block and am having trouble with the plugs fouling.
Snip 

In the Champion line of plugs using the following format where the 
number 12 is the recommended heat range, a larger number would 
be a hotter plug. ;

RC12LYC Champion recommend plug base bottom line plug.

Thus a hotter plug one heat range hotter would be a

RC13LYC  plug. 

While changing to a hotter plug is a recommended fix for fouling, it 
is also a band aid to cure a problem that may have some other 
rational for causing the fouling. 

While I do not use a 4.0 head on my 1975 or 1980 258 AMC I-6, the 
recommend plug is an RN13YC which is a resistor/copper electrode 
plug the car gives me no problem using RN9YC plugs. 
Are you also burning quite a bit of oil?
John.



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