Farm Equipment - WC spark plugs

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WC spark plugs

Printed From: Unofficial Allis
Category: Allis Chalmers
Forum Name: Farm Equipment
Forum Description: everything about Allis-Chalmers farm equipment
URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=203874
Printed Date: 28 Jul 2025 at 11:38pm
Software Version: Web Wiz Forums 11.10 - http://www.webwizforums.com

Topic: WC spark plugs

Posted By: Mark.Kuehn
Subject: WC spark plugs
Date Posted: 28 Oct 2024 at 5:16pm

I'm attempting to find modern replacements for AN7 or AC45 plugs.

I read that Champion J8C is possibly an equivalent and so is NGK CS3. Is this true, and what have others used successfully?

If the plug is a match for depth (length), diameter, and thread is there a risk of using an equivalent plug?

Replies:

Posted By: JoeM(GA)
Date Posted: 28 Oct 2024 at 5:32pm

I run Autolite 295’s in my WC

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Allis Express North Georgia
41 WC,48 UC Cane,7-G's,
Ford 345C TLB

Posted By: PaulB
Date Posted: 28 Oct 2024 at 6:12pm

The NGK equivalent for an AC45 is a B6S non resistor, if you want a resistor plug use a BR6S.

Back in the 70s I quit using Champion plugs for anything. In a box of 10 you could be sure 2 were bad, it was up to you to find those 2.

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If it was fun to pull in LOW gear, I could have a John Deere.
Real pullers don't have speed limits.
If you can't make it GO... make it SHINY

Posted By: Steve in NJ
Date Posted: 28 Oct 2024 at 6:47pm

Autolites or NGK's are usually the strong picks for AC Tractors. Autolite 295's are a warmer plug. The other Autolite choice that can be used is the 303. These are a little colder plug. Worn engines or engines that have some time on them where oil control may be a little bit of a problem, the 295's work great. The NGK B6S work great also. The choice is yours...

Steve@B&B

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39'RC, 43'WC, 48'B, 49'G, 50'WF, 65 Big 10, 67'B-110, 75'716H, 2-620's, & a Motorhead wife

Posted By: Alberta Phil
Date Posted: 29 Oct 2024 at 10:33am

Your WC should have a magneto unless it's been replaced with a distributor. Magnetos don't like resistor plugs or carbon core wires!

Posted By: ekjdm14
Date Posted: 07 Mar 2025 at 7:26am

Another "vote" for avoiding resistor plugs here. Paul, you stopped using Champion way back when. In a similar vein I stopped using any NGK resistor plug about 20 years ago. Not bad out the box but you could be sure at least 50% of those would fail within a month of regular use & seemed extra sensitive to fouling too compared to the non-resistor types.

I've spent way too much time broke down at the side of the road or not getting started cold, all down to the resistor plugs somehow even when they were what the book called for. Nix the "R" part of the number & never an issue.

Posted By: Phil48ACWC
Date Posted: 07 Mar 2025 at 10:29am

The best plug I've found for my WC is NGK Iridium and best price is from Rock Auto. Part number XR4IX and Stock number 7189 at $5.97 Each. Brick and mortar parts stores are at least twice that price. I have a distributor on my WC and the Iridium plug I referred to is a resistor plug. About 5 years ago I did a complete overhaul on the engine in my WC. It has a WD-45 crank with aluminum WC pistons (makes it about 8:1 compression ratio), triple angle valve job, port work and port matching to get balanced flow between all cylinders, new sleeves and pistons and rings fitted to the minimum end gaps and all the usual close attention to the rest of the engine. (I've been building engines for all of 50 years), I used a completely overhauled Delco distributor with new bushings, new cap and rotor, Pertronix conversion, new resistor plug wires etc, etc. This is a new engine with a few tricks for better performance and reliability. I put in a new gapped set of Autolite 295 plugs. First start up and break in went very well. Ran great under power etc. At idle there was a slight miss indicated by the exhaust flapper flapping on occasion. Carb adjustments didn't get rid of the miss. I then put a timing light on each plug wire and noticed #1 cylinder had a slight misfire. I swapped #1 and #4 plug and the misfire moved to #4 cylinder. Ah ha plug misfire. I then put in a set of the NGK Iridium plugs per above, recommended on this site in the Pulling Forum. After that the engine ran perfectly and the exhaust flapper sat still at idle. The sweetest running WC I ever heard. As said that was five years ago. Those plugs are still in there and running great. Iridium plugs last a really long time because there is far less electrode erosion and the fine wire positive electrode heats up quickly at start up to help eliminate misfire and provide clean running. I now run NGK Iridium plugs in every thing I own. Now granted, would I have noticed the misfire in a stock WC engine doing regular chores? I 'm not sure. My WC is used year round in central Vermont with weather ranging from 90 to -20 degrees F. If this tractor doesn't run, we don't get out in the Winter. I'm a believer in NGK Iridium plugs.