Carb float settings

[1946]

I Have a problem with what I think is the carb float setting. I have a rebuilt motor 40th over (self built), runs very nicely, but drive on the road or go down a steep drive ,it some times has a habit of what appears to be flooding. I have been told that an amount of black smoke comes from the back of the car.
On trying to track the proper setting, I have found two answers, one, from the centre flange on the float to the carb body..1 inch, from the top of the float to the carb body 5/8th inch. Also a warning do not bend the float arm!. There is a fixed pin through which the arm rotates, so the more or less washers under the valve for adjustment changes the float angle. what is the proper setting please.

 

[Brentwood Bob]

Tom Endy covers the float setting in this technical article.
http://www.santaanitaas.org/wp-content/uploads/2014/08/The-Zenith-Carburetor-11-07.pdf

 

[johnbuckley]

Toms Endy's article is excellent.
For Zeniths 5/8 inch is the usual advised level of the fuel below the upper casting,usually when the top and midline solder seam of the float are parallel with the machined face of the upper casting, BUT the weight/displacement of floats varies a bit so the only way to be sure of correct fuel level is to use the glass jar method that Tom shows in his article. [this can be done with the carb on the car if LHD- difficult if RHD... I use a slice of old inner tube to hold the jar in place whilst checking] . You may need one, two or even three gaskets +/- half thickness gaskets between the valve and the casting as various valves vary in their height. A kit of shim gaskets can be bought from the usual suppliers.
later edit: YBlockhead in post #7 below is absoluetly right... the fuel gauge he shows is a very useful inexpensive kit for quickly checking fuel level.

 

[Ed in Maine]

You might also look for the float level tool that consists of a clear plastic tube and fitting that screws into the drain plug hole. It is very cheap. You place the tube along side of the carburetor to see the level. The benefit of this tool is that you do not have to disassemble the carburetor. I believe the 5/8 in. dimension is between the top of the machined surface of the lower casting and the level of gasoline in the bowl. Some carburetor repair manuals say that the critical thing is to keep the Compensator Jet covered at all times even when you are stopping at a stop sign and gas is surging forward in the bowl. I usually try set my gas level 11/16 in. below the top of the machined surface to avoid gas seepage when parked heading down hill.

 

[Bob Bidonde]

These slides should help you.

 

[History]

To check my float height (with bottom of carb removed) I used zip ties and attached a clear glass jar to the bottom of my carburetor and hooked the fuel line up and turned it on. I guess you can make a mess this way but it worked well for me. I had a helper turn the fuel on and was ready to turn it off. After the float needle stopped the flow I unhooked it and could visually see where the height was set.

 

[Y-Blockhead]

Renner's Corner has a nice float level 'gauge'. Available for Zenith, Tillotson and in my case Marvel Schebler. You can see here my level is a little high.

 

[johnbuckley]

Whilst we're talking fuel levels ... where should the fuel level be on Tillotsons? Most books etc suggest the float bottom should be 1 inch from top casting when float valve closed... but where does this put the actual fuel level?

 

[1946]

Thank you all for the great knowledge you have given. I forgot to mention the fuel tank is in the rear of the car and has a rotary vane fuel pump (12v) feeding the normal fuel filter on the fire wall. The pump is only supposed to deliver between 2 and 4 psi. I am also going to try an adjustable fuel pressure regulator to see if pressure is part of the problem.
Thanks again for all the help. I will take this opportunity to wish you all a Happy and Safe Model 'A' Christmas.