Allis Chalmers B plug wires

[kearly]

My new to me 1938 Allis Chalmers B runs very rough. Will be changing the spark plugs, but wondering if the plug wires might be on the wrong plugs. Anyone have a diagram or experience with this?
Thanks

 

[used red MN]

Hello kearly, welcome to YT! Ha, ha “kearly and curly” that is clever I can only guess that is your intention. Right off let me tell you I’m an IH and Farmall guy so my knowledge about your machine is limited or next to zero. I am pretty good at gleaning the net for answers. Here is a link to a diagram found for your question, click the underlined word “info”. Info
In case you don’t know number 1 cylinder is nearest the fan. They are labeled for the model CA, but the list at the bottom of the diagram
includes the B. The problem is I don’t know if that shows the stock orientation of the distributor cap. Depending on who put the engine together your distributor may or may not be positioned the same as this diagram. If the distributor cap has a 1 by its terminal tower where the number one plug wire is connected to then the chances are pretty good the rest will follow suit by rotation of the distributor as shown. Other than that if number one plug wire is currently on the wrong cylinder that makes it all a bit tricky. If you change the spark plugs and it still runs rough check back and we can dig into it deeper. One thing you might consider is when you have a plug removed hold your finger or thumb over the spark plug hole and crank the engine. It should repeatedly pump against your thumb like a bicycle tire pump. When you do this pull the coil wire out of the distributor cap and tuck it somewhere near a metal part to ground out the spark. If you have a magneto leave it in the kill position because most magnetos don’t have a coil wire. If one or more of the cylinders does not pump air (have compression) then that will require more investigation. Also marking which cylinder the plugs came out of and posting a picture of the part of the plugs that is inside the cylinder can tell us things. I also have some other information I would like to share with you. At the top there is a “letter or mail” icon. That is the personal messaging for the forums. When a number shows on it you have a message. Give it a look!

 

[Jim.ME]

My new to me 1938 Allis Chalmers B runs very rough. Will be changing the spark plugs, but wondering if the plug wires might be on the wrong plugs. Anyone have a diagram or experience with this?
Thanks

Welcome to the Forums.

A search online will turn up several sources of scans of the original Allis Chalmers service manual for the G, B & C, and CA. All four were in the same AC Manual. There are also some scans of the old I&T manual as well. If you are going to pay for one, the hosts of this site sell printed manuals

As used red MN mentioned knowing you have a distributor, not a magneto (those tractors could have used either), and having #1 in the right place to match the compression stroke are key items.

 

[used red MN]

Jim, the manual is what I sent him in a PM, but not an I & T . What I found in the manual about the ignition was only a description by words.

 

[Jim.ME]

Jim, the manual is what I sent him in a PM, but not an I & T . What I found in the manual about the ignition was only a description by words.

Like many other manufactures there was another manual with basic info. The AC Manual I mentioned refers to the loose "Farm Equipment Service Manual". Page numbers for info, in that publication, where available are noted in the right-hand column of the index for each model. I have been keeping watch to find a copy of that manual, but no luck so far. The basic ignition info in the IH manuals you have posted before should help him if needed.

 

[stevieb49829]

My new to me 1938 Allis Chalmers B runs very rough. Will be changing the spark plugs, but wondering if the plug wires might be on the wrong plugs. Anyone have a diagram or experience with this?
Thanks

Is there a firing order cast into the head of the engine? From there, if you know which way the distributor or magneto turns it's easy to check if the plug wires are where they belong. steve

 

[Fixingfarmer]

1-2-4-3

 

[Pappy]

My new to me 1938 Allis Chalmers B runs very rough. Will be changing the spark plugs, but wondering if the plug wires might be on the wrong plugs. Anyone have a diagram or experience with this?
Thanks

To learn everything about an Allis Chalmers B, Go to Rod's website. www.rodnh.byethost12.com. This is the best source on the net. Many pages of useful information.

 

[Pappy]

My new to me 1938 Allis Chalmers B runs very rough. Will be changing the spark plugs, but wondering if the plug wires might be on the wrong plugs. Anyone have a diagram or experience with this?
Thanks

To learn everything about an Allis Chalmers B, Go to Rod's website. www.rodnh.byethost12.com. This is the best source on the net. Many pages of useful information.

 

[kearly]

Thanks! Will do.

 

[kearly]

My new to me 1938 Allis Chalmers B runs very rough. Will be changing the spark plugs, but wondering if the plug wires might be on the wrong plugs. Anyone have a diagram or experience with this?
Thanks

Amazing what new plugs, a clean fuel screen, and fresh fuel can do for a rough engine!

 

[DSMHONEYYARD]

Also, make sure that you have the correct type of plug wires. The must be copper core. The newer type don't work well with a magneto type of Ignition.