Tilly Carburetor

I will also buy your core Tilly model X for up to $25 including shipping or Zenith $50 including shipping if complete. Deduct $10 if no carburetor driver. Deduct $15 if no throttle shaft. Deduct $8 if no choke shaft.

This is a model X or XF. Sometimes they are not marked.

This is an F1-B that looks like a Zenith. I don't want these as replacement parts aren't available

This is a Marvel-Scheiber. I don't want these as replacement parts aren't available.

Tilly carburetors are easy to restore. Take them apart, soak in carburetor cleaner, bead blast, clean out the passages, replace any broken parts, and put in some new gaskets.

Places in the top to clean out with a piece of wire.

I use a piece of 0.024inch MIG welding wire.

This is the idle circuit. Remove the 3/8inch welch plug, clean, and replace.

There are 2 small holes to clean with a piece of wire here as well.

Clean this passage with a piece of wire.

There are 3 lead plugs that need to be taken out to clean the passages. I replace the plugs with a piece of lead solder pounded in to seal it off.

The large hole in the center is where the main nozzle goes. I have had to drill out about half the main nozzles. The drill bit is the passage for the adjusting needle.

I sand the top of the upper casting and top of the lower casting on a stationary belt sander to flatten them. The upper casting top is often warped when the mounting bolts are over-tightened. This is better than the Zenith which breaks off the ears!

Taps: 7/16-20 for float valve, 3/8-24 for main nozzle, 5/16-18 for mounting bolts, 12-32 for main jet, 1/4-32 for idle jet,1/4 pipe for gas inlet. You won't find the 12-32 and 1/4-32 at your local hardware store. I bought mine on Fleabay. A couple of gaskets and the 3/8inch welch plugs

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On the left is the float, the choke and throttle shafts.

On the right is the float valve, main jet, main nozzle, adjusting needle, idle needle, body screws, mounting bolts and lower plug

1112

Gasoline Leaks

Sometimes Tillys leak. Be sure and close the gasoline shutoff valve when you park your Model A. Leaking gasoline is dangerous and can cause fires and explosions!

Possible causes of leaks are:

1-Sticking float valve. Get a new float valve, especially one with a viton plastic tip. A sticking float valve will cause the carb to leak out of the main nozzle when the gas shutoff valve is opened. The entire 10 gallons of gas may leak out if the gas shutoff valve is not closed when the A is parked.

2-Float not set correctly. I set the float a little low at 1 1/8inch to try to avoid leaking out of the main nozzle.

3-Picture 7 Drain plug. Replace gasket but be careful not to tighten too tight and strip the threads as the casting is aluminum not cast iron like the Zenith.

4-Picture 7 The lead passage plug may leak (drill bit is show in the passageway.) Peen the lead plug or replace it.

5-Picture 8 The lead passage plug may leak (drill bit is show in the passageway.) Peen the lead plug or replace it.

6-Inlet gasoline connecter. If it leaks here, try tightening the connecter but if that doesn't work, get a new upper casting.

7- Upper casting warped. This is a common problem that can cause leaks. I take a hammer and beat on the upper casting with the upper and lower casting screwed together. Works every time for me! You can also use two gaskets.

Harder parts of restoration

- The main nozzle can sometimes be difficult to remove and must be drilled out. If find this on about half of cores. Start with small bits and work up to larger ones. Chase the the threads with a 3/8-24 tap.

- The main jet at the bottom of the float chamber may also have to be drilled out. Chase the threads with a 12-32 tap.

- Mounting bolt holes are often stripped. Use 5/16-18 helicoils, special tap, and inserting tool to repair them.

- Choke arm nuts. These are an odd size, 8-36. The parts houses have them. I got mine at Graingers.

How a Tilly works

· GAV on the left with the driverr is the main gas control. It can block off the gas from the bowl. Gas from the GAV flows thru the bottom horizontal passage in the picture to the main nozzle. Brass plug at bottom seals the main nozzle (not pictured).
The top half shows the welch plug and the two small holes that go to the throttle passage. This circuit is the idle adjustment. Air goes thru the two small holes. At the bottom of the passage below throttle there is also a small brass plug with a hole that goes to the air space of the fuel bowel. The barely visible hole in the bottom middle of the vertical passage is where the idle air adjustment screw is inserted into.
· Idle screw is for air trim adjustment. · There is a metering orifice opposite the idle screw that lets air into near the end of the main nozzle barrel. This air is used to aerate the fuel in the main fuel nozzle · With the car at idle, the throttle is closed and the throttle blocks off the lower of the two small holes behind the welch plug (the top circle in the picture) close to the throttle shaft. All the gas for idle is sucked up by engine vacuum thru the vertical passage below the welch plug thru an orifice in the small brass plug nearest the bottom of the top half from the lower threaded end of the main nozzle in the lower half. When the throttle is opened engine vacuum can now suck gas thru the main nozzle. At the same time the lower of the two small holes (0.025 and 0.033 inches) behind the welch plug is opened and more gas flows as well thru the idle circuit. There is a metering orifice opposite the idle screw that lets air into near the end of the main nozzle barrel.
The bottom half shows the small main jet in the fuel bowl and the main nozzle. The horizontal passage near the bottom of the main nozzle is plugged off with a lead plug. News to me was the end of the vertical passage has a hole to the main nozzle passage.
The main jet(0.040 inches) is in the bottom of the fuel bowl shown at the left and meters the gas to the main nozzle or high speed jet shown on the right. The 8 holes(0.030 inches) in the main nozzle or high speed jet help to atomize the gasoline. Gas to the GAV is metered only by the GAV as there is no jet to meter it in the fuel bowl only a hole

This is what the final product should look like.