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QUESTIONS
Which check ball does the 1940 use?

The 1940 uses 1 check ball which is 1/8" diameter. This is put in the main discharge hole and then the check weight goes over the ball. Be sure you have room for the check weight to move up. About 1/16"
I have a customer that wants to put a 1940 on his econoline but he is going to use a DUI distributor and he want to know what to do with the spark control valve. Someone told him to put a power valve where the spark control valve goes.

Any ideas on this one?

No need to do that, just leave it or if he wants he can plug it. Should work just fine.
Is the Holley 1940 correct for my vehicle?

The Holley 1940 was used as a replacement carburetor for the Autolite 1100 carburetor. The 1940 was also used on a lot of industrial application. Wood chippers seem to come up a lot. There is nothing wrong with using the 1940. In fact in some respects it is a simpler working carburetor than the Autolite 1100 is.
I have a 1940 Holly, have completely rebuilt it thanks to your excellent video..Had a "professional" take a look even.. However, it will not idle at all?? Seems like the only fuel it gets is from the main jet and acc pump-nothing else??

Make sure the idle mixture screw passage is clear. Might be clogged somewhere in the Idle mixture circuit. Take the screw out and blow through it. Can you feel air through the small hole in the bore?

Next cover the hole in the bore and blow through the screw hole. Air should go through into the float bowl.

Get some thin wire and clean out the passages.
1940 Spark Control Valve

Not all Holley 1940 carburetors have a spark control valve. For those that don't you may find the recess for the valve, but there will be no threads.
Accelerator Pump Does Not Return

When pumping the accelerator pump, the pump does not return. This is most likely due to the spring being installed incorrectly.

1940 Accelerator Pump
Assuming you are using the new spring in our premium kit, it should look like the one in the illustration. There is a recess that the pump moves up and down in and you want to make sure the spring sits on top of the recess and isn't going down into the hole.

The other thing that might be a problem is the pump cup may have curled up when being installed. That will cause it to bind. Try spraying some silicon spray lubricant into the well when installed so that the pump slides in easily.


Carburetor isn't getting enough fuel.

1940 Fuel
  • Test the fuel pump - new pumps are especially suspect. Should be around 4.5 lbs.
  • Look for any kinks in the fuel line.
  • If the vehicle has been sitting for more than a few months, then the gas has probably turned and coated the inside of the carburetor with varnish. This means the small passages may be plugged.
  • Check the float level - Different specifications for different engines, so look at the instruction sheet of the carburetor kit, or your motor manual.
  • There is also a float drop. Be sure that is set. I have seen them set so little that the needle doesn't have any room to open.
  • Check the float to make sure it isn't rubbing on the side. They fit fairly snug in the float bowl.
  • With the top off, turn it upside down and see if the needle falls down easily. Any sticking is a problem.
  • Be sure the retainer is in place. The retainer holds the float in position.
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