Carb choices

German guy

German guy

Senior Member
Not wanting to start a fight here...but...


Can we get some discussion on pros and cons of up vs down draft carbs?



I installed a 6.1:1 cast iron head and the FSI "Zipper" carb for more power to make driving in the VERY hilly German wine country easier...but fuel delivery seems to be the next step, preferably coupled with a cast iron header for the outbound gases.


My goal is to keep engine appearance as original (not show car level) as possible while maximizing performance. My initial thought was a Weber but unless there is some way for it not to stick up so high and 'in your face' with that massive chrome topped filter, I tend to look for other possibilities.



I am no more than a VERY basic mechanic with no experience with machining parts to fit....so I probably need a kit.
 
The stock Model A with the original carburetor is a wonderful thing. It is fun to drive and nice to look at. The Model A with the Weber and other modifications is also a nice car but different. It all depends where your head is at.
 
My experiences with a Weber have been positive, but the carb and intake manifold will definitely take your car out of the realm of looking original. My late 1931 Deluxe Roadster did not need a fuel pump because of the way the fuel exits the gas tank in a straight line, unlike earlier gas tanks that have a 90-degree angle change in the fuel flow. You lose the pushing pressure of the gas mass when it has to stop and make a detour before going to the carb, besides passing through a sediment bowl on the firewall. A late '31 by-passes all that. I drove cross-country through mountains in that Roadster and never once did the carb starve for fuel.
However, moving the same carb and manifold setup to my 1928 Phaeton required a fuel pump. The car would only go for a block or so before the carb starved for fuel, even on level pavement. If I coasted, the fuel would flow enough to drive a short distance again. And then sputter and die again. Unless your Tudor is a late 1931 with direct fuel flow from the tank, plan on adding an electric fuel pump to handle those mountains of yours. And those 6-volt fuel pumps are loud!
Also be aware that you will need to buy an expensive Rube Goldberg accelerator linkage to make the throttle work. It looks clunky, but works. And yes - you can buy all these parts as a kit. The fuel pump will need to be purchased separately, I believe.
Marshall
 
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I have rebuilt several zenith carburetors using Dave Renner's set of precision nozzles that have been flow tested. This seems to be working very well and keeps the orignal look as Neil indicates. <Rennerscornerfarm@yahoo.com>
 
I know you asked about carburetors, but…
What is the head’s compression ratio? If climbing hills is the goal, along with appearing stock, a high compression head may be an answer. I presume shipping and duties will raise the cost so this idea may not be useful.
Edit: I just read your question about oil pan gaskets, and see you already are running a 6.1:1 head. Never mind.
 
A high flow carburetor, such as the Weber, will make a difference at higher rpm. Up to about 1,500 rpm there is no difference between the normal updraft carburetors and the high flow carburetors. The higher compression head will add torque throughout the rpm.

If you have a high flow carburetor and an engine that can reach the higher rpm, you can use 3,000 rpm or more to climb steep grades or as a shift point when using the on-ramp.
 
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