Spark plug choices

[73chgrSE]

There are so many different types these days. I haven't bought any since last century. What should I get?

Stock 400 magnum.

[c00nhunterjoe]

Stock champions or autolites will be fine. Nothing fancy is needed on a bone stock setup. There is nothing to gain in this situation.

[69wannabe]

I have grown to like the NGK V power spark plugs in my charger and in my Jeeps too. The XR 5's will probably be the right one's for the 400.

[73chgrSE]

I currently have champions RJ12YC in. Must be running rich because they look blackend even after I took them out, cleaned them and put them back in for only a day then checked them again. I don't wanna put new ones in until I can iron that out. I guess the carb needs some tuning.

[c00nhunterjoe]

I ran the champions for years in my 12 second 383. Nothing wrong with them. Black is bad, definitely needs some tuning.

[ODZKing]

I have always used Champions. but last go round someone suggested NGKs, and I went with those. No difference and by the time I got thru with shipping they were same price as Champions locally.
You say 400, 2 or 4 bbl.  They are different.
2bbl is J13Y
4bbl is J11Y
And if you can find original numbers, better yet.

[73chgrSE]

I have always used Champions. but last go round someone suggested NGKs, and I went with those. No difference and by the time I got thru with shipping they were same price as Champions locally.
You say 400, 2 or 4 bbl.  They are different.
2bbl is J13Y
4bbl is J11Y
And if you can find original numbers, better yet.

4 bbl.  Yes I have the glove box book with the original #'s and also the Haynes book with only the Champion #'s. I was just looking at other brands/options. I ended up getting the same Champion ones that were in it from the last tune up. J12YC although the old ones said "RJ12YC" not sure what the R was for but the J12YC came up as the same ones.

[birdsandbees]

Get on EBAY.. someone will have some real OEM J-11-Y's for sale...

[jlatessa]

"R" is for resistor type...Joe

[73chgrSE]

What's the real difference between a J-11 and a J-12?

Resistor type seems unnecessary since there is no computer in the car right?

[ODZKing]

What's the real difference between a J-11 and a J-12?

Resistor type seems unnecessary since there is no computer in the car right?

True, but also helps with noise in the radio. But if you have resistor wires it doesn't really matter. The non resistor plugs will give you a little better voltage from what I've read.

[jlatessa]

11 is the colder plug of the two, also resistor plugs can help firing a difficult mixture
from what I remember.
Something to do with additional power build-up because of the spark having to jump the gap within the plug tower??

Just from my somewhat faulty memory....

Joe

[c00nhunterjoe]

The resistor has zero to do with performance.  It has no effect on the burn. It is solely for rf interference.

[Ghoste]

Not to mention that jumping an extra gap makes no sense either.

[firefighter3931]

There are lots of things that can cause dark plugs ;

- Carb adjustments/tuning
- Spark plug heat range too cold
- Weak ignition system with excessive resistance

How old are your plug wires ? One thing I like to check is the quality of the spark. Try grounding a plug wire and turning the engine over looking at the color of the spark : white/blue spark is good....yellow/orange is weak spark indicating excessive resistance. If you have a weak spark break out the ohm meter and measure resistance on each wire. If you're seeing more than 250 ohms per foot the wires should be replaced.

On a low compression engine a warmer plug is your friend. I'd be inclined to use an NGK XR4 plug on a low compression 440 which is what you have. That vintage 400 is most likely under 8:1 compression so a warmer plug will help.


Ron