Jet sizes of Zenith Bendix 9786D wanted

[ThomasBorchers]

Hello all,

 

we own a 1929 Hansa A6 which is fitted with an engine by Continental. Original carb. was a Stromberg UX2 but our is totally rotten. There are some of these cabs on the market but really expensive.

 

I found now a Zenith 9786D which could be ok for us.

 

Good to know is the size of the jets. Has someone information about this?

 

Or perhaps has someone an idea which carb to use instead of the Stromberg?

 

Kind regards

 

Tom

Edited July 27, 2015 by ThomasBorchers (see edit history)

[ThomasBorchers]

Need still help--- We have installed the Zenith carburetor above but the problem is, that at idle rpm the mixture is too lean, at 1300 rpm it is 10% CO, too rich. Has someone the size of the jets or eben a hint what to do?

 

Kind regards

 

Thomas

[Ivan Saxton]

I am fairly sure that Dykes, or Dykes Carburettor Supplement has a fair bit of data on zenith. The first aspect you nned to attend to is verification that the carburettor throat, and the venturi size are within range of size for the engine, and the way you want to drive it. Stromberg also have charts of size for number of cylinders and piston displacement. Zenith give diagnostic tests to show by driving tests on the road how you need to alter what you have. If you cannot find what you need, send me a private message an I will get the stuff scanned so I can email it to you. I apologise that I can only send things by email, because the ability email picture files is illogical to my understanding of logic. One thing you can do is check that the fuel level is just below the top of the jet.

[ThomasBorchers]

Hi Ivan,

 

after testing a while ( the carb ist still in place at the car ), the funny thing is : You can turne the mixture screw as you like, it makes no different. Even when the engine is runnig, you can pull full choke : Makes no different! If the engine is running, it has full power, has a smooth idle and the spark plugs elektrodes look great. Could be that the engine goes off at a traffic light. If this happens : It is not possible to start the engine again. Just if you use some start spray...

 

For me at the moment... it is a mystery.

 

Kind regards

 

Thomas

[nickelroadster]

Sounds like a question for carbking.  Send him a pm.

[carbking]

The problem may be more than jetting.

 

I have no records from Stromberg on Hansa.

 

I have listings that Continental used the Stromberg UX-2 on three engines: 14-C, 15-C, and 16-C. All are listed as a 6 cylinder 248 low RPM engines.

 

I have listings for Zeniths for the same engines, however, they are all physically smaller than the Zenith 9746, which is a type 63AW11 which was used on a later G.M.C. of 248 CID, but capable of higher RPM than the Continentals, therefore possibly internally larger than the UX-2.

 

The internal specifications for these units are on microfilm rolls, and time-consuming to access.

 

I would suggest to the original poster that he check the internal venturi size of the UX-2 used on his Continental and compare that to the venturi size of the 9746 which he is attempting to use. As stated before, the physical size is not the determining factor in air flow. The internal venturi is the major control for air flow. It is possible a carburetor with a different venturi may be a better choice. Or maybe not, but before making calibration changes, would be a good idea to check both venturii.

 

Other considerations:

 

The fact that the idle screw adjustment is doing nothing is telling you something, normally that the mixture is overly rich. What are you using for a fuel pump? How much fuel pressure at the inlet valve of the carburetor? Depending on the orifice size in the 9746, the maximum pressure the carburetor is going to like is maybe 3 psi.

 

The UX-2 is a cross-flange carburetor. I think (not positive on this) that the 9746 is a straight-flange carburetor. Are you using a 90 degree flange adapter? If so, this drops the carburetor requiring more negative pressure to lift the fuel for starting. When starting after a stall are you using the choke, which would augment the negative pressure?

 

Jon.

Edited September 28, 2016 by carbking (see edit history)