float level setting on tillotson carb

Pepsi Mechanic

Pepsi Mechanic

Senior Member
I occasionally have a small fuel leak from the tillotson carb on our 28 engine after shutting down . I have noticed that if I shut the fuel valve off before I shut down the engine and let the fuel get used up in the bowl for 30 seconds or so the fuel leak is no more . I recently rebuilt the carb but did not realy know the float level setting ( basicaly I guessed ) Is there a setting ? And is this the probem ?
The truck gets driven by several different people and I want to make sure all is safe .
P.S. the fuel system is clean
 
1" float setting for Tilliston; top half held upside down & measured from surface of casting flat where gasket sits,

Good luck,
 
Measured from surface of casting flat where gasket sits to what? Asking because I just rebuilt the Tilliston on my A. Now its idling rough, but best with the idle screw all the way in. Stalls when I back it out more that a 1/2 turn. Idle smooths out considerably with the manifold vacuum line open.
Runs fine at higher rpms

My thinking is it is running too rich due to hight float level Thats why it smooths out with the vacuum line open. I just kinda guessed on the float level.

So, my question, float level measured from surface of casting flat where gasket sits to what? No horizontal seem on my float.

thanks
 
A lot can happen to cause a Tilly to run terrible.
Float level, From the top carb flange upside down the top [ which is actually the bottom to me] of the float is suppose to be 1". I find that a bit high and set it to 1 1/16" to lower the level a bit. Bend the arm squarely as near the float as possible, try to keep the arm as parallel as you can across the valve.
These critters are noted for warping and the warps can usually be filed out. The halves need to fit together almost correctly and the mounting flange should be as flat as possible to help eliminate a vacuum leak.
Its hard to get them clean around the main jet and it doesn't always want to come out in one piece [ 3/8X24 if I remember correctly]. Sometimes it needs to be drilled out and replaced. There are several passages in there that need to be cleaned and removing that jet is about the only way to do it.
Make sure everything is square and fitting correcting as well as being really really clean and these old carburetors work well.
 
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This is my preferd method, and this way the Zenith measurment is 5/8".
Thanks to Tom Endy.

"A test jig can be constructed that the top housing is attached to. A fuel supply is added above it and a supply line connected to the fuel inlet. A glass container is attached beneath to allow the fuel level to be observed. When fuel is allowed to flow into the glass it will rise until the float valve shuts it off. The level can then be
measured to determine if it is 5\8” down from the bottom of the housing. A mark is placed on the glass at the fuel level and the carburetor is allowed to sit static for a period of time to determine if the float valve is holding or allowing fuel to creep up in the glass."​
 

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May sound strange; however, if one would have asked a vintage extremely intelligent mechanic how to adjust the float level on "any" car in say 1930 this is what he would have advised:

1. Remove the carburetor & split the halves.
2. Make sure the float valve moves freely when the float is moved up & down.
3. Turn the carburetor upside down, ("any" make, "any" car), & look at the horizontal seam in the float.
4. Adjust the level of the float such that the horizontal seam line in the float is exactly parallel to the mating seam line where the two (2) carburetor seams meet together.
 
Ok Stateside, let's have the definitive answer... Paul Mollers book Model A Carburetors states for Tiollotsons (page 52) ... when upside down .." one inch from the machined edge to the float bottom." but on page 53 says when right way up..." fuel level is 3/8" below the gasket line". Which is right as the 1" method gives about 5/8 inch; the 3/8 inch method gives under an inch ???
 
Thanks for all the replys. I understand much better now.

Sprayed carb cleaner in the needle seat area and all around inside the carb. There may have have been some sediment in there. I then set the float to 1 inch as per your advices. Much better.:)

2 more questions if I may (this is a Tilly carb)

1 Any suggestions on setting the idle. Idling rough now, but excellent at higher rpms/speeds

2 Any suggestions on an inline filter for the stock gravity fed set up. I now have the glass bowl with the screen in place.

Again...thanks.
 
If it runs rough at idle, then its not set right, you may have a vacuum leak or the insides are not clean. As mentioned these are prone to warpage.
I install an in-line filter next to the shut-off with no ill effects.
 
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