Spark plug question

I have a '63 F-head in my CJ-5. I have just gotten the beast on the road after a year-long rebuild. I have posted before that the #4 cylinder is fouling plugs. I think I have some oil control issues in that cylinder. So I got one of those anti-fouling extensions from my flaps and it seemed to work. Oh, brand new plugs too (AC 45r). I drove about 30 miles this weekend and pulled the plugs to check the mixture of my new carb. Plugs 1-3 looked great, but #4 had burnt/melted the electrode. No other physical damage can be seen.

Any thoughts on why the elctrode melted?

BTW, I got a Solex carb to replace the well-worn Carter, what a piece of cake to install and tune! No tinkering involved.

 

can you post a pic of the damaged plug ?

 

Was your jeep originally 6 volt? I consistently fouled my #1 cylinder while running the original 6 volt coil but 12 volt everything else(plugs may have been 6 volt too). I got a 12 volt coil and plugs and it ran much better. Question - Is the AC 45r a 12 volt plug?

 

I've never heard of 6v vs. 12v sparkplugs.:? Coils, sure. Don't plugs get hit with umpty thousands of volts when they fire?

 

Yes! The coil steps the voltage up from whatever is put into it, based on 6 or 12v (or nine with a Ballast Resistor) to a much higher voltage depending on the individual coil. Some are more, some are less.
Plugs don't know what the coil started with!

 

I have attached a picture of the plug. I had already removed the melted part from the tip, sorry. The Jeep is 12 volt from front to back. The plugs, AC Delco R45's, are what the repair manual reccomends.

 

in my opinion
defective spark plug
or
debris/carbon stuck to tip, causing excessive/higher than normal voltage spike, which melted the plug tip

what brand and weight of oil are you using ?

 

X2, It sure looks likes a pre-ignition/lean damaged sparkplug.

 

boschh platinums..only thing i run.

 

EEEEEWWWWWWWW! I've had more driveability issues created by those #$%^%^E$ plugs! I wouldn't put those in my lawn mower if you paid me.

NGK, Motorcraft, AC, are mostly what I run with very good results. No damn split fires, and unless the application calls specifically for it, no platinums. Nickmil

 

wow. i put a 48kv hei on mine and kick the platinums and it never hesitates to start and NEVER miss fires.... ran em on a 65 fairlane 289, 84 gmc 350 and my jeep. best thing i ever installed..

 

detonation would of blown the grounding electrode off too. I believe you will find it was a defective plug. Try another plug. The built in resistor was probably the problem. Can you ohm out the plug yet? If so, check to see if it is the same as the other 3. Try NGK or Champ's?

 

Thanks for all the replies. I'll check the resistance in the AM. I'm hoping that it was just a defective plug. What kind of luck must I have that out of 4 new plugs, I put the one defective plug in the cylinder that I'm having problems with.

Anyway, does anyone have a Champion or NGK plug number for an F-head? The FLAPS only shows the ACDelco plug.

Thanks again.