Firing Order 1948 B Allis Chalmers

gdtractor

Member
This message is a reply to an archived post by rob bass on January 04, 2014 at 21:39:38.
The original subject was "Re: Firing Order 1948 B Allis Chalmers".


Allis C
The order on the distributor [mag] plug wires should be
#1 cylinder on the top left distributor hole (sitting on tractor seat) ..?
#2 cylinder goes to the right TOP plug wire hole ?
#4 plug wire goes to the righ lower plug wire hole?
#3 cylinder then goes to the lower left (all of the above - sitting on tractor)?
are the above correct? assuming #1 is TDC .. etc ..

For some reason I can't find this info online . (obviously looking in wrong place .. :) ...)

thanks
Gary
 
All of this will depend on how the gears are clocked. You will have to determine direction of rotation firing order and location of tdc. Think the marks on the flywheel. Also assuming you have the factory mag there is a gear and rotor under the top cover.
 
That is the correct factory position of the wires. It is a question the has came up often over the years. It is the same on a magneto except the cap is 90? tipped down from the distributor.

BulidingAllisEngines004-vi.jpg
 
Hmmmm .. so the #1 cylinder wire goes to the upper LEFT side (sitting on the seat) ...

When I got this tractor (and the mag is identical to the one in the above pic) ... the #1 plug wire and #2 plug wire are switched from this pic ...

So .. the pic above IS the RIGHT way for a magneto plug wiring on an Allis C ?

THanks much .

Gary
 
That is a picture of my one C but all the B's and CA's are the same. On the distributors you can time it fire number one plug from any cap terminal you would like real easy. It does screw with the next owners mind if they are not an engine mechanic when they jerk of the old plug wires off and start to install new ones.
 
Rotation CAN be off from this and the engine will run, IF the distributor or Mag isn't set right to TDC of #1 cylinder.
If any 2 wires are switched, you WILL have a miss and the engine won't run right.
 
Thanks much .. I think I have it figured out finally .. ha !!

#1 cyl is set at the 2nd position on distr cap .. but it turns clockwise so I think i have it .
thanks a gain

Gary
 
I wrote this article many many years back concerning timing a magneto, the tractor referenced in the story just happened to be an AC C. B and C engines were identical in this respect.
Magneto Timing
 
Wow!! Thanks so much .. I REALLY needed this .. I was kind of "stuck" as to what to do next !!
I will print it off as well .. THANK YOU SO MUCH Gary
 
It wasn't firing the way it was wired so I found the TDC mark on the left side ..

the Rotor at TDC was pointing to where the #4 plug wire would go IF #1 plug wire was in the first position .. so I CAN put the #1 plug wire in the 3 position then #2 then #4 then #3 CLOCKWISE order right?

THanks Gary
 
ONe more thing .. I suppose the plugs is not a big thing .. but the ones that I have in it are the same plugs used for lawnmowers around here .. some are even the little short ones .. CHampion J8C or something like that . I wonder if when I spray the starting fluid on them I am getting them too wet?
What do you think?

Gary
 
also .. what is the gap on the plugs please . ?
can that make a big difference?
I got new ones . but the only thing O'reilly's had was the lawnmower plugs . :)

Gary
 
any info on this video
I cannot find any "marks" as to where to turn the interlocking gear ..

I have the the flywheel set at "Center" on the little opening on the left side .
There is also a line with the word "Fire" on it too .

can you help ? Thanks

http://www.youtube.com/watch?v=cT_MbNjC0bU
 
Most auto parts stores will only carry what would be called a lawn mower spark plug that would be not resister. The gap for the plug should be .035.
To (set the magneto) you would want the fire line about to show on the (compression stroke) on number one cylinder. The magneto would want to be ready to fire number one the next time the impulse snaps.
After the magneto is (set) (bolted in place) you will want to check for spark at number one cylinder by turning the engine over and when you are on the compression stroke for number one and you hear the snap and (see) the spark you want to see the CENTER or TDC line in the inspection hole. Most all engines cold time to TDC on number one cylinder car truck or tractor regardless of make.
Leave the spark plugs out until you have proven you have spark at the proper time at number one cylinder. I place the magneto in a bench vise and with plug wires all in I snap the magneto over with a wrench and check for spark with each wire holding the wire close to the magneto base. When I know I have good spark and the next snap will be to the number one wire I tape the impulse so it can not turn. This has it ready to set on the tractor just before the Fire line starts to show. If you let the impulse turn back it will fire on the terminal before number one.
 
Are the fire & center line close together?
(I know I could look , but thought I would ask the expert first). Ha
Gary
 
I just looked at your video! I have had some that were not marked also. I have not repaired a magneto in ten or so years. I have always had several magnetos in parts and would hold the rotor in the position that it was on a marked gear. I have several in a box out in the shed that If I can get back in there with my walker I'll see if I can tell you an easy way to mesh the gears correctly. The metal gear had one tapered tooth on the face. I an not sure at this point if it is up or down the way you were holding the magneto in your video. I am thinking up but not sure. Maybe Steve from B&B will check in and help with that.
 
Thanks SOOOOOO much .. that had me really stumped!!
Took my mag in to a repair person .. to make sure it was fixed right ..
then I will put it on with the TDC position and tweek it from there ..
a friend didn't think it had much "snap" to it . so I thought I should get it looked at .

thanks AGAIN ..

Gary
 
If you put the flywheel on CENTER before you try to bolt your magneto to the block you will not get the drive to line up because of the impulse spring. You first set it to the FIRE line or even back the engine up a little so when the magneto drive lugs line up you do not have tension on the impulse spring. Then after you have the magneto bolted fast you find the Center line in the inspection hole when you spark on number one cylinder at the compression stroke. If you do not see the Center line you rotate the magneto a little until you have the Center line in the center of the inspection hole. If do it this way when running with a timing light you would see the FIRE line in the center of the inspection hole. Your magneto has a 30? mechanical advance. When cold timed at TDC the advance places the FIRE line in the center of the inspection hole when running at high idle. I always take these steps when installing a magneto to prove to my eyes I have it timed to run. Many will say it is not necessary to take this step. Just time it by ear after it starts. I learned thru my many mistakes that I personally can not assume anything. The extra time for me to prove things out saves me time in the long run.
 

We sell tractor parts! We have the parts you need to repair your tractor - the right parts. Our low prices and years of research make us your best choice when you need parts. Shop Online Today.

Back
Top