Running very rich

[howie123]

I have been working on a similar problem. At 25-30 mph the engine would start to spit out the tailpipe and the plugs were always coated with black soot. Since it started after I installed a fuel pump, the pump was blamed. The pump pressure was only 1 psi so I started troubleshooting the ignition. I thought I had a good spark but when checking the timing again I got a strong blue spark about every third time the points opened. I spread the connectors on the coil wire to make a tighter fit and cleaned the contact areas. I took a 30 mile drive today with no spitting. I will drive it a while before checking the plugs but I am optimistic that I found the problem. Thanks Purdy for the advice. Howie

[Purdy Swoft]

Originally Posted by Harley03joe

PURDY:
Great Write Up Thanks
Harley03joe

Joe ,Thanks for the kind words!!!
Purdy.

[Purdy Swoft]

Originally Posted by howie123

I have been working on a similar problem. At 25-30 mph the engine would start to spit out the tailpipe and the plugs were always coated with black soot. Since it started after I installed a fuel pump, the pump was blamed. The pump pressure was only 1 psi so I started troubleshooting the ignition. I thought I had a good spark but when checking the timing again I got a strong blue spark about every third time the points opened. I spread the connectors on the coil wire to make a tighter fit and cleaned the contact areas. I took a 30 mile drive today with no spitting. I will drive it a while before checking the plugs but I am optimistic that I found the problem. Thanks Purdy for the advice. Howie

Thanks, Howie for the kind mention, I'm glad that it helped.

[lenandmy40]

I have a 31. I live at 6800 feet in Colorado. I built my carb (Zenith) to the specks I've never had trouble with it. This sounds like a condenser problem. I use 85 octane (this is what the blend is for this altitude) regular unleaded fuel and stock spark plugs. Should you have paper air filter it's to fine not enough air. Use the original wire mesh filter. With paper I was getting about 10 mpg. With the wire mesh I'm getting about 17mpg. with paper air filter you will need about 18 inches of length to get the proper air flow. Len

[JOES31]

I second ED S. on changing to the new Zenith 13922.

[GrandpasA]

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Originally Posted by Purdy Swoft

I can't see how float level will have anything to do with whether it runs rich or not . If you raise the float level high enough it will cause the engine to starve for fuel under load. With the float too high it would run lean and backfire but it would not run lean and smooth . If the float level is too low it would cause leaks and stalling apon braking or coming to a stop but wouldn't cause the engine to run rich as you describe. If the running rich problem began after installing a carburetor kit, that will more than likely be the problem. I would try replacing the jets that you removed. The jets in the kit may be too large. The knob on the choke rod controls how rich or lean the engine runs. Make sure that the knob on the choke rod is tight and not just spinning on the choke rod shaft. Turn the knob clockwise to lean or counter clockwise to richen the mix . Zenith carbs usually run best with the GAV knob turned 1/4 turn off the seat when warm. The adjustment screw with the spring on the front of the carburetor housing controls the air mix for the idle circuit . Tightening the screw richens the idle circuit, loosening the screw leans. The idle air adjust screw usually idles best with the screw one and one half turns off the seat.

I wonder what spark plug that you are using. I had similiar problems when running Motorcraft TT 10 or Champion W 16 Y spark plugs on short stop and go drives. Champion W 18 spark plugs are hotter and run cleaner for most model A short around twon drives. I would take a look at the air gaps between the rotor tip and the contacts in the distributor cap. An air gap of .035 will give you a hotter spark at the spark plugs and help better ignite the fuel and burn off the soot. If the coil is weak and the heat range of the spark plugs is too cold, the spark plugs will continue to run black and sooty . Most times running rich gets blamed on the carburetor . I have found the problem to be weak ignition in most cases. ust my thoughts.

your words here have helped me dearly, next on my list is changing out the spark plugs, can i get those at any auto store?

[Purdy Swoft]

Thanks for your kind words!!! Yes you can get the Champion W 18 spark plugs at any parts store that sells Champion spark plugs. NAPA can usually get them over night. The order number for the Champion W 18 is 518

[GrandpasA]

thanks, I'm ordering the plugs tomorrow..

[chrisabes]

Hi Chris Van, In addition to the great advise given in the previous messages, I would suggest having a look at the following link. I have just found it and will certainly be reading it.
http://www.model-a.org/jet_flow_testing.html
Re. your altitude of 6000', I can certainly relate to the problem having lived in Zim.