The Zenith Carburetor

Here's a link to an exceptional collection of information on anything related to the Zenith carburetor. I wish I had found it before trying to learn a lot of it the hard way.

Look around the website. There are numerous categories to help, with clickable links within them that share good tips.

Armed with this and Tom Endy's excellent article you should be able to handle most issues with the carb.

http://www.model-a.org/default.html
 
Looking at the link TJMack has provided, I saw this in regards to shutting down an "A".

https://www.model-a.org/shut_down.html

1. Engage emergency brake by pulling back on it.

2. Push Left Lever (Spark Control) all the way up (retard position)

3. Push Right Lever (Throttle) all the way up

4. Turn Gas Valve under dash on passenger side to closed position (pointing to the Left).
If vehicle is going to be left over night, or similar circumstances, it's a good idea to let the engine burn up the majority of the gasoline in the carburetor by letting engine run until it stalls.

6. Turn Off the Lights and any other Accessory

7. Turn Ignition Switch off (Counter Clockwise)

#4, ... I unserstand the turning off of the gas valve, but why would you want to run it out of gas if your going to drive her again the next day or in a couple of day's? A week or more of sitting I understand, ... but the way they put it, I see no reason what so ever to follow #4. ALSO running an engine out of fuel tends to be something you don't want to do.

Is there something I'm missing here?

Regards
Bill
 
Bill, it looks like they are assuming the tank valve leaks. If it leaks, then it needs to be repaired. The first winter I owned my 29 Tudor, the tank valve and carb needle and seat both has small leaks, and I lost a full tank of gas. I lapped both valves with toothpaste and haven't leaked a drop in the past 20 years.
 
Hi Tom,

I get that part, ... but draining the carb or running out of fuel is only something you do for storage to prevent lacquer build up from gas degradation.

What advantage does this have on a daily basis other than running your car extremely lean, something we need to avoid.

Regards
Bill
 
BillCNC said:
Hi Tom,

I get that part, ... but draining the carb or running out of fuel is only something you do for storage to prevent lacquer build up from gas degradation.

What advantage does this have on a daily basis other than running your car extremely lean, something we need to avoid.

Regards
Bill
Click to expand...



If the tank and carb valves leak just a tiny bit, the carb bowl can fill during the night, and might not overflow and leave gas flowing out the carb to drip on the floor.
 
Like I said, I get the gas shut off, and if it is shut off, no gas will get to the carb if the valve works correctly. If it doesn't draining the bowl or running the carb out of gas is pointless it will just fill up again throughout the night.

On the other-hand, if you have a perfectly functioning gas valve, ... there is no point in running it out of fuel or draining the bowl. it's a waste of time, gas, wear and tear on the carb drain plug and leaves a door open to the possibility of issues due to running it lean every night.

Regards
Bill
 
BillCNC said:
Like I said, I get the gas shut off, and if it is shut off, no gas will get to the carb if the valve works correctly. If it doesn't draining the bowl or running the carb out of gas is pointless it will just fill up again throughout the night.

On the other-hand, if you have a perfectly functioning gas valve, ... there is no point in running it out of fuel or draining the bowl. it's a waste of time, gas, wear and tear on the carb drain plug and leaves a door open to the possibility of issues due to running it lean every night.

Regards
Bill
Click to expand...

I haven't noticed any leaks in my carb, but my experience is that if I park the car in an enclosed garage I can definitely smell gas the next morning, and my wife lets me know about it.

If I let the carb run dry, I don't get the gas smell so I think that validates that 1) I don't have a leak in the valve or the carb, and 2) the gas is evaporating from the carb.

David Serrano
 
Tom and Bill both have good concerns. My experience with a possible gas leak on the garage floor is a nightmare especially with the gas hot water heater and garage heater pilot lights with my wife and I sleeping upstairs. :eek::eek: The valve shutoff on my roadster is on the outside raised firewall and I believe it the same one Tom is referring to that he laps with toothpaste. I also believe these valves work great when lapped correctly...however the gravity fed carb can have lots of issues as have been discussed here. The one issue that comes to me and is just my opinion is that little bit of gravity is just enough to test some valves and seats when there not just perfect. My fix was a POSITIVE in line shut off valve from Brattons for about 50 bucks. Connects to the bottom of the firewall valve and the other end directly to carb. Shuts the gas off COMPLETELY....no guessing. So please fellas don't mess with a valve that may leak, to scary for me. :eek::eek::eek: Dutie
 
Heat soak can be a problem. Today's crap gas, and even the better gas without corn, evaporates and boils too easily compared to the good gas of the 60's. During a hot shut down the carb absorbs engine heat and the gas in the carb boils, so running it low helps to not get gas boiling over and out the carb throat.
 
A speck of rust is all it takes to cause a problem. The run it dry takes a minute, why not do it. Your life or property damage is enough reason for me. After loosing half a tank by not doing it I learned my lesson.
 
TinCup, thanks for posting that link. That animation is fantastic. So are Tom Endy's two articles. I've saved them all for future reference.
 
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