Zenith carb adjustment on 1933 10/4

This forum is for non members to ask questions to the ATDC Members. Members should use the private forums for any and all Member to Member conversations.
Post Reply
Petetherod
Posts: 13
Joined: Thu Jun 02, 2022 6:30 pm

Zenith carb adjustment on 1933 10/4

Post by Petetherod » Fri Jul 01, 2022 6:13 pm

Hi. My car is running extremely rich and the mixture adjustment made no difference when being turned in or out on the carb. So I decided to get a quality rebuild kit for the carb as it did have slight movement on the spindle. Having now cleaned and fitted all the new parts the car runs ok but when trying to tune and balance the carb the mixture screw makes no difference when being adjusted in or out. Any ideas would be appreciated. Thanks

6350_William_French
Posts: 97
Joined: Wed Nov 20, 2019 10:27 am

Re: Zenith carb adjustment on 1933 10/4

Post by 6350_William_French » Fri Jul 01, 2022 9:07 pm

Hi if you take the mixture control screw out completely and when the car is ticking over you should feel with your finger that air is been pulled in to the hole. If not something is wrong. And putting your finger over the hole should change the engine tickover speed.
The mixture adjusting screw ONLY changers the fuel/air mixture at tick over speed it has no effect on the fuel/air mixture when the car is running normally above tickover speed, and all old Austin engines run rich you will not get nice clean brown plugs as you do on 1960 cars.
from Bill

Petetherod
Posts: 13
Joined: Thu Jun 02, 2022 6:30 pm

Re: Zenith carb adjustment on 1933 10/4

Post by Petetherod » Fri Jul 01, 2022 9:47 pm

Thanks Bill. I’ll try your suggestion. What I did notice that next to the mixture screw there is a tiny hole, if I put my finger over it it does make a difference to the engine note.

Austin ollis
Posts: 31
Joined: Tue Dec 24, 2019 12:51 pm

Re: Zenith carb adjustment on 1933 10/4

Post by Austin ollis » Sun Jul 03, 2022 2:24 pm

Hi
The carburettor is getting its air from another source, even though you have fitted a re build kit I suspect air is still passing the spindle because of wear in the body of the carburettor a simple test would be to start the engine and spray WD 40 around either end of the spindle if air is still leaking past the spindle you will notice the engine tone change for a short period of time as the WD40 stop the air been drawn in around the spindle the same steps can be carried out around the manifold gasket as this is another possible place for air to leak if its the spindle the carburettor needs re sleaving if its the manifold gasket it needs replacing stop the air leaks and you will be able to adjust you carburettor properly hope it all makes seance and good luck.

Regards Austin Ollis

Post Reply