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AC Model C Carb

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=125902
Printed Date: 18 Jul 2025 at 8:22am
Software Version: Web Wiz Forums 11.10 - http://www.webwizforums.com


Topic: AC Model C Carb
Posted By: kd8ajc
Subject: AC Model C Carb
Date Posted: 14 Jul 2016 at 10:33am

I have a 1947 Allis Chalmers model C and I rebuilt the Zenith carb from a kit. It went back together just fine but gas keeps draining out the air intake ports on the right.  The Needle Float Valve is the same size and shape as the original.  Am I to assume the floats are not raising high enough to push the needle valve up into the brass barrel that houses the valve in order to shut off the flow? The new floats are almost identical in size, shape and positioning as the original.  

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Replies:
Posted By: Dick L
Date Posted: 14 Jul 2016 at 4:17pm
Dirt is the normal problem that causes this or a bad rubber tip. Without actually having the carburetor in hand I wouldn't know the cause.

I set the floats buy eye upside down level with the base and blow with my mouth on the inlet to check for it shutting off.

 

Posted By: Steve in NJ
Date Posted: 14 Jul 2016 at 5:52pm
I preach this all the time, but one of the biggest problems with dirt and debris is the inlet port to the needle and seat needs to be spotless. Dirt, rust, and debris build up in the unused threads where the 90 degree elbow screws in. Also, the inlet port walls, and the back of the inlet port trap rust, dirt, and debris and the new Viton needle valves catch that minute dirt and it hangs the valve open. The end result is flooding and or overfueling. The best thing to do is remove the Carb, lift the top off and run a bore brush in a drill in and out of that bore till it shines! Once all the rust n' muck is outta there, you should be good to go. While you have the top off, take the pivot pin out, shake the floats gently to make sure they are not taking on fuel. If they are, you will hear a sloshing noise inside the floats. This would cause the same problem and a set of floats are in order. HTH
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


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