NOS dud plugs

[dpledger]

Completing my long restoration of '53 Manhattan, I put in NOS Champion J8 plugs that I found online. Were all sealed and looked fine. After only a couple of hundred miles I have had to replace 2, and now things seem to be running rough again. One actually had a little spark going under the boot, and the other had developed quite a lot of resistance. I'm surprised that a plug could deteriorate when sealed in the original container. Has anyone else experienced this effect?

[HJ-ETEX]

I am concerned. Were these J8C plugs or actually NOS J8 plugs? I have been taught that the base on the original J8s were black and there was a difference in the number of ribs (and height) on the porcelain insulator as compared to the later J8s that had bright bases.
J8C means the plug has a copper core and not a carbon resistor core. You shouldn't have arcing or other resistance effects if you use these.
J8C spark plugs are usually sold singly because currently their main use is as lawnmower spark plugs.

[dpledger]

These are marked Champion J8 The ceramic has 2 ribs above the Champion and 3 below. The bases are bright, and there is a made in USA and 322 engraved. These looked like the plugs I always used in antiquity, which weren't carbon core. These, now that you mention it, behave as tho they were carbon. I'm now thinking that these are sort of an intermediate age, after carbon started being used. Still wondering why they would deteriorate so fast after being installed even if carbon.

Have noted the J8C's, but wasn't sure if they would perform exactly like the old J8's, being sort of put off by the lawnmower applications. Need to do something, as these are going fast. Maybe after 60 years of using them in the car I should move to Autolites?

[njpatera]

J8C is a normal size plug...I just looked on the shelf at work...just put them in mine...There is a lawnmower size(shorter) equivalent too. J8C is used in many applications auto, truck, as well as ag...We have them in 4 Pks or even 24 if needed...

[dpledger]

Thanks for all the info. Will get to replacing with 8C's asap. Still puzzled as to why even carbon cored plugs would lose it in sealed storage. Guess maybe I never used such in a case where it had been sitting very long.