The Ford Barn

H. L. Chauvin · 10-09-2015, 11:32 AM

I remember hearing of many complaints about Model A Zenith carburetors years ago when Model A's were daily drivers rather than show cars, and how the Marvel carburetors were bought and thought to render better performance.

FWIW: There appears to be several possible reasons why so many thousands of Marvel carburetors were sold "immediately" after they were offered by Sears, Western Auto, etc., and why evidence of these many sales are exemplified today in offering them on E-bay:

1. Appears so few Mechanics and Model A owners would take all of the time required to "properly" rebuild a Zenith with worn out air leaking throttle shafts, worn needles and needle seats on GAV's, and properly cleaning out partially plugged inner carburetor orifices.

2. New Marvels were not only functional, they were very inexpensive to purchase.

3. With proper Ford recommended carburetor very low idle settings, (and never having to fiddle around with the GAV and the throttle prior to sudden stops), rectangular Marvel bowls never caused engines to "die" at stop signs like the fuel sloshing round bowl design with Zeniths.

4. Engine flooding, engine stopping, and having to restart engines at every stop sign were not tolerated by Model A owners back then because at this time, Model A's were a "main" source of transportation as opposed to less used show cars needing an original Zenith.

5. These guys back then were far more interested in the Marvel's advertised better performance rather than showing off an original Ford Zenith.

Maybe in looking back at this era, the wonderful part of the rest of the story, is that later, dedicated "Restorers" wrote detailed instructions on how to properly restore a Zenith, and how to correct this round bowl engine fuel flooding with the lowering of the float level.

Seems like in the end .......... "all" types of Model A carburetors are as different and unpredictable as new wives ...... you either get a good one ..... or you don't ...... but, when you get a good one ........... no explanation is needed.

Mark in MT · 10-09-2015, 11:43 AM

My experiences with the Zenith are that if you are idling too fast, it is not running on the idle circuit. This can be because the throttle plate is not positioned right in the bore. If the air at idle is not forced right by the discharge port for the idle, you have to increase the idle screw to get it to run. This makes it run on the cap jet circuit which is more sensitive to sudden stops. Adjust the plate in the bore to get it to cover the idle discharge port and you can get it to idle at 400 rpm and do so while standing on the brakes.

10-09-2015, 11:32 AM	#21
H. L. Chauvin Senior Member Join Date: May 2010 Posts: 4,179	Re: No more stalls at stop signs for me! I remember hearing of many complaints about Model A Zenith carburetors years ago when Model A's were daily drivers rather than show cars, and how the Marvel carburetors were bought and thought to render better performance. FWIW: There appears to be several possible reasons why so many thousands of Marvel carburetors were sold "immediately" after they were offered by Sears, Western Auto, etc., and why evidence of these many sales are exemplified today in offering them on E-bay: 1. Appears so few Mechanics and Model A owners would take all of the time required to "properly" rebuild a Zenith with worn out air leaking throttle shafts, worn needles and needle seats on GAV's, and properly cleaning out partially plugged inner carburetor orifices. 2. New Marvels were not only functional, they were very inexpensive to purchase. 3. With proper Ford recommended carburetor very low idle settings, (and never having to fiddle around with the GAV and the throttle prior to sudden stops), rectangular Marvel bowls never caused engines to "die" at stop signs like the fuel sloshing round bowl design with Zeniths. 4. Engine flooding, engine stopping, and having to restart engines at every stop sign were not tolerated by Model A owners back then because at this time, Model A's were a "main" source of transportation as opposed to less used show cars needing an original Zenith. 5. These guys back then were far more interested in the Marvel's advertised better performance rather than showing off an original Ford Zenith. Maybe in looking back at this era, the wonderful part of the rest of the story, is that later, dedicated "Restorers" wrote detailed instructions on how to properly restore a Zenith, and how to correct this round bowl engine fuel flooding with the lowering of the float level. Seems like in the end .......... "all" types of Model A carburetors are as different and unpredictable as new wives ...... you either get a good one ..... or you don't ...... but, when you get a good one ........... no explanation is needed. Last edited by H. L. Chauvin; 10-09-2015 at 11:37 AM. Reason: typo

10-09-2015, 11:43 AM	#22
Mark in MT Senior Member Join Date: May 2010 Location: Western MT Posts: 218	Re: No more stalls at stop signs for me! My experiences with the Zenith are that if you are idling too fast, it is not running on the idle circuit. This can be because the throttle plate is not positioned right in the bore. If the air at idle is not forced right by the discharge port for the idle, you have to increase the idle screw to get it to run. This makes it run on the cap jet circuit which is more sensitive to sudden stops. Adjust the plate in the bore to get it to cover the idle discharge port and you can get it to idle at 400 rpm and do so while standing on the brakes. __________________ Mark in MT Always looking for another opportunity to be wrong.