Champion J8C Spark Plug cross reference

[southcoasting]

Found this very interesting sheet cross referencing plugs from different manufacturers for the Champion J8C plug:

http://www.ihcubcadet.com/IHCCFAQ/SparkPlugCrossReferenceChart.htm

[Dave Neptune]

Good find

southcoasting, nice find. I knew the NGK number but not the rest. Do you know of a crossreferance or suffix for the "R" (with resistor) series regarding other manufacturers?
I could probably look them up however I won't bother until I can't find the RJ8C's.
Thanx for the post and info.

Dave Neptune

[rrranch]

Are they supposed to be the ones with resistor or without on this engine?

[Dave Neptune]

J8 j8c rj8c

rranch, makes no differance as far as heat range, it's just a matter of choice. I doubt resistor plugs were even available when this engine was designed.
There are far more choices today even in wires.

Dave Neptune

[southcoasting]

southcoasting, nice find. I knew the NGK number but not the rest. Do you know of a crossreferance or suffix for the "R" (with resistor) series regarding other manufacturers?
I could probably look them up however I won't bother until I can't find the RJ8C's.
Thanx for the post and info.

Dave Neptune

As far as I know, the NGK cross reference for the R Champion plug is BR6S, which is actually cheaper than the Champion R plug itself...

I also found this cross reference for the NGK BR6S plug but not sure how accurate it is as the Champion cross reference shows as RJ6C instead of RJ8C: http://www.gadgetjq.com/spark_plug_c...motorcycle.htm

[southcoasting]

I could probably look them up however I won't bother until I can't find the RJ8C's.

Amazon has em at $6 each with free shipping...Champion 871's

[Dave Neptune]

Thanx

southcoasting, thanx fopr the heads up on Amazon. I can still get them at my local NAPA store and ony need a set every few years. I usually run 2~3 seasons on a set, maybe 200 hours or so.

Dave Neptune

[H3LlIoN]

Sweet find. Napa can cross reference any plug too. I changed out/threw out three sets of Champions and had them crossed to the NGK's.

[sastanley]

Check out this site.

https://www.sparkplug-crossreference.com

[Mo]

I checked something out.

Shawn,
I just had a look around on the NGK site because I use NGK XR4 plugs. Here`s something of note. NGK numbers...the lower the number the hotter the plug.

NGK B4L (extended nose is .44 inch)
CHAMPION H10C
CHAMPION RH18Y
CHAMPION RH10C

NGK XR4 (extended nose is .38 inch)
CHAMPION RJ14YC
CHAMPION RJ18YC

so...the NGK XR4
...X =booster gap / extended tip or nose
...R =resistor
...4 =heat range ... hotter in this application.
...and the extended nose is .38 inch (something I was surprised with)

This is probably why they work so good in my engine... here's what a booster gap is supposed to do:

A final variation on the basic spark plug theme you should know about is something NGK calls a "booster gap," and is known at Champion as an "auxiliary gap." By any name it's an air gap built into a plug's core, and it improves resistance to fouling. Conductor deposits on a plug's insulator nose tend to bleed off the spark coil's electrical potential as it is trying to build itself up to spark-level strength. If so much energy is shunted in this way that firing does not occur we say the plug is "fouled." It is possible to clear a lightly fouled plug by holding the spark lead slightly away from the plug terminal and forcing the spark to jump across an air gap. The air gap works like a switch, keeping plug and coil disconnected until the ignition system's output voltage rises high enough and is backed by enough energy to fire the plug even though some of the zap is shunted by the fouling deposits. Mechanics discovered this trick; plug makers have incorporated it into some of the plugs they sell, and booster/auxiliary gap plugs work really well in bikes with an ignition system strong enough to cope with the added resistance. Such plugs more or less mimic the fast-voltage-rise characteristics of CDI systems - and offer no advantage used in conjunction with a capacitor-discharge ignition.

There's lot of info on this stuff out there...just have to sift through it.

These plugs went in my engine May 2011 and I didn't have any problem all summer...absolutely no fouling either. So my plan it to run these for another while, pull them frequently to see how they look. Other NGK plugs on the market are XR5 & XR6...running cooler as we move up in numbers. The XR4's were recommended by Nova Automotive here in Dartmouth NS (they do rebuilds) and they said they had great results with them. Any ideas or concerns greatly appreciated....I'm just in a learning curve on this myself.

[sastanley]

Mo...I'll let you know how it goes..I have the NGK BR6S plugs, which cross reference to the Champion RJ8C.

I've run everything from the RJ8C's (in the boat when I got it), to Autolite 303s, & the hotter Autolites (438 maybe??), to Champion RJ12YCs..(currently in the boat.)

I decided to go back to the RJ8C equivelants based on some of Dave Neptune's discussion that he sees better power with the RJ8C's. The NGK's are cheaper than the Champions, and I've always had good luck with both Champion & NGK in my vehicles.

I quite honestly haven't noticed a real difference in any of the plugs, but I've been so pre-occupied with all the other issues with the motor, like just getting reliable spark to the plugs, that I haven't been able to focus on which plugs seem to perform the best.

[Ajax]

My R8JC's were badly fouled and came with the boat, plus I seemed to be missing some power off of the top end, so I replaced them with RJ14YC's to help with the fouling issue.

Then I discovered that my distributor had slipped way back, retarding the timing, which was the cause of my loss of top-end power.

The RJ14YC's are not fouling, quite the opposite: They seem too white at the tip, indicating that they are too hot. Now I gotta go find a cooler plug so that I can achieve that perfect, tan color that plugs are supposed to be.

[Mo]

? multiple factors

Hi Guys,
Last spring I put AC delco plugs in and one went in about a week...that's when I went to Nova looking for B4L's. The boss guy pulled both the XR4 and the B4L out and showed me the difference...all I could tell was the number. Then he mentioned that the XR4 won't foul as much....they didn't foul at all. So that's where I am with it right now....he also realizes I run without a T-stat here and I imagine our water might be a few degrees cooler. You know, it could be a combination of my running with no T-stat (by-valve open about 1/2), our cooler water temps, carb tuning...and god knows what else, that makes this work for me.

We will see how it goes. I believe the engine is tuned in better than ever and certainly is part of the equation also. Can't say I ever had much problem with anything, just last summer spent some time tweeking. Prior to that I'd start up, pull off the dock and go about 300 feet, pop the sails and engine off. It's still that way

[sastanley]

My R8JC's were badly fouled and came with the boat, plus I seemed to be missing some power off of the top end, so I replaced them with RJ14YC's to help with the fouling issue.

Then I discovered that my distributor had slipped way back, retarding the timing, which was the cause of my loss of top-end power.

The RJ14YC's are not fouling, quite the opposite: They seem too white at the tip, indicating that they are too hot. Now I gotta go find a cooler plug so that I can achieve that perfect, tan color that plugs are supposed to be.

Ajax, my #4 cylinder is a little weaker than the others and I get some black oily stuff on that plug. I think this is due to the partial drowning(s) this motor has seen. The P.O. reports having to scrape rust off the #4 cylinder wall to get the engine freed up, so I would assume there is some pitting and probably some oil getting by the rings, especially in that cylinder. What I tend to do is every time I take out the spark plugs, I rotate them, usually putting #1, which seems to be in the best shape and most 'normal' looking, into #4.

I wonder if there is any issue with running different plugs in different cylinders? Like, run a hotter plug in my weak #4 to keep it from fouling and the normal heat range in the other 3..I am guessing the coil & EI unit would not like that a whole bunch.

[Dave Neptune]

No biggie!

Shawn, the EI won't care a bit!! It is a common practice to go a bit hotter on weak oily cylinders so why not(?). I would suggest a hotter plug without an extended tip, it will reduce the exposure of the porcelean and help keep it cleaner. There are "anti-foulers" available which just space the tip back so you can use the same style plug and just go a step hotter, a bit MM but they do work.
Won't hurt a thing!!

Dave Neptune