over running carburetor ?
 

Bought a rebuilt Zenith carburetor 4 yrs ago which until recently worked well. Usually when I park my '29 coupe I turn the brass valve off in the cab so that the float bowl is empty. A week ago I didn't follow this routine and noticed that gas was coming out the rear opening so I ordered a new Viton tipped valve and installed it with the same washer that was used with the original.... still leaked !! so, removed the carb and increased the washer thickness with a very thin grey washer... still leaks !!!!! All of the float standards in Float standards in Les's book are met..brass float with no leaks


My question: Do I have a defective valve? Should I increase the washer count? do I have a "burred" seat ? Many Thanks for your capable help.

IndyA

Re: over running carburetor ?
 

Float level, or poor seat in the Valve would be my guess.
What was the source of the 2nd valve? New?
Early ones had filings embedded in the Viton.
This was in a Tom Endy technical article.
Try one thing at a time. So try another washer with the old valve.
Then try the new valve with old washer, then with added washer.
Then test float for leak.
Dirty fuel?

Bad shutoff had not occurred to me. Indy mentioned a week of leaving the valve open led to a leak problem.

Re: over running carburetor ?
 

Re: over running carburetor ?
 

Also look for other sources of a leak, such as the jets. It may be necessary to rebuild the complete carburetor with new gaskets.

Re: over running carburetor ?
 

the procedure is to first check the float valve.
this can be done by
-shut off the gas at the tank
-leave the carb on the motor
-remove the bottom/bowl of the carburettor.
-leave the float on.
-find a glass jar that fits over the float and valve assembly,
-elastic or tie it onto the carb with the float and valve inside it
-then open the valve at the tank.
-the gas should fill that jar to 5/8" from the top, and stay there.
-if it does and after you put the carb back together and gas still runs out the back of the carb, the cap or main jets are to short. or no washers to seal them
-if gas keeps rising in the glass jar then the float is set wrong or float valve washer is leaking or the valve itself is not working.
-this will enable you to watch the float as well to see if it is rising properly.

this is the start of the leak process, this is very abbreviated but it is the way to check the float inlet valve.

some of the service manuals show this process and is a good idea to have one on hand and follow. i have stumbled through a problem such as this then realised that the book was smarter than me.

ou

ps
i don't shut the tank valve off on my car in the summer, it should not drip out of the carb.

Re: over running carburetor ?
 

The float level needs to be correct and is set with the washer[s].

Those viton valves did have a filing contamination issue at one time. Some could be cleaned by flushing.

With the carburetor bowl removed the valve can be checked manually. Place a container under the carburetor. Turn on fuel and work the float with your finger very gently. Raise it to seat it and see if the fuel flow stops completely. Work it numerous times to flush it and check it.

Another place to look is the float arm where it contacts the needle. Over the years a dimple can be worn into the arm. This can be carefully sanded smooth.

Re: over running carburetor ?
 

Check the shut off valve under the tank for seepage. Disconnect the line to the carburetor and place a container under the line. Leave it for a while to see if the valve leaks.

I have found in the past that if the shut off valve has slight seepage there is not enough
head pressure/flow to keep the float tightly against the needle valve.

I know that sounds backwards but every time I come across this problem and changing the float needle valve does not cure it, it is the shut off valve.

Re: over running carburetor ?
 

Thank you all...I'm very impressed with Ruth's and Ol Ugly's reply (they don't use the brass cut off when not running)... I think I'm going to follow that practice for a while. I did change the gas to a single nylon one that came with the original carbureator and .... no leaks????
Indy A

Re: over running carburetor ?
 

this is a good little book to have if you are working on your stock carb.

Re: over running carburetor ?
 

Also see http://model-a.org/default.html