Tillotson Model X vs Zenith 2 sidebowl

Sunny the Model A

Sunny the Model A

Senior Member
Howdy Y'all, got a question I'm sure has been beaten to death, so I am going to put a new spin on the old debate of zenith vs tilly. I am currently running a zenith 2 sidebowl on my late 31 pickup, I heard the general consensus is that the tillotson model x carb generally yields better fuel economy, my question is, how much better mpgs should one expect from a tilly? I daily drive my pickup and am running stock head with stock cam, 160 thermostat, reground valves with spark advance at ford specs usually halfway down on the quadrant and gav shut or cracked going uphill. I usually drive around 30-35 which is right where it likes to drive with the 4.11s. Would it be a good investment of my fuel dollars to throw a good tilly on it that has been gone through. my zenith sidebowl is giving me about 15 mpg mixed driving right now in the colder weather. I want to try to squeeze as much fuel economy as I can out of it since I'm a cheap son of a gun. and I always love to tinker. If there is another updraft carb that might yield better fuel economy, let me know. Sidenote, I am going to put a mitchell 26 o/d in it, but I can't afford it at the moment, so any info from y'all is much appreciated.
 
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My first Model A came with the Zenith side bowl which was correct for the '31 Slant Windshield and I thought it ran good enough. Then a friend gave me a nice Tillotson and I noticed that it seemed to respond better to throttle input and idle. I bought a Roadster back in June, and it came with a Tillotson and it ran great too. Then I traded another carb for a Marvel Schebler and I couldn't believe the difference in the way the car accelerated and idled - better than the Tillotson for sure. I don't have any data to support fuel mileage yet, but I don't see any dramatic difference in fuel consumption. Needless to say, I'm sold on the Marvel.
 
interesting, is the marvel schleber still reproduced or are they all used? I always want to make sure I can get parts before I invest in something. I know they are not original looking but as long as it works with the stock manifold and is easy to find parts for, I might invest in one. I was looking at the internal parts of the zenith, marvel, and tilly, I like the design of the multiple jets of the zenith the best, but I like the bowl design and simple assembly of the tilly better. I suppose the marvel is the best of both worlds. I am not a lead foot and am mainly looking for reliability and economy in these cars, so if anything that simply bolts on to the stock A adds to fuel economy or to reliability without modifications to the car is always something I'm willing to consider.
 
I have rebuilt Zeniths, Tillotson Xs and F1Bs, and Marvel Schebler carbs; in my opinion the Marvel out performs the other carbs for the Model A.
If you are considering installing a Mitchell overdrive, they offer a 36% unit which would probably work well with your 411 rear. Give Steve Mitchell a call, I sure he will be more than happy to help you.
Norm
 
Norm M,
I completely agree with you on the performance of the Marvel. I have all three carburetors and they are all in good shape and adjusted properly - in fact, you would be hard-pressed to detect the difference in performance if you didn't do a back-to-back test. I did a test one day to prove it to myself. After running the Zenith with the car up to temperature for a couple of miles and noting its performance, I came home and immediately changed over to the Tillotson and did the same thing. Came back home and immediately changed over to the Marvel...and there's no doubt about how much better the car ran with the Marvel.
 
I've driven Model A's for 55 years. I've run worn out Zeniths, well-rebuilt Zeniths, brand new Tillotsons, worn out Tillotsons, and well used Marvels. I've run bone stock engines, a police head, a Brumfield head, and a Snyder 6.0 head. I always get 16 miles per gallon no matter what. If your main concern is fuel economy, you should concentrate on the jet sizes in a well-rebuilt carb of any brand. (Changing jet sizes and flow testing jets and reboring jets is WAY beyond my ability and understanding.) But if you really want to address fuel economy, replace the 4.11 with a 3.73, or add the Mitchell overdrive, or both. That's going to do more for fuel economy than merely switching stock carburetors around. Especially since you are on flat ground, that 4.11 is only good for pulling stumps.

W. Michael
 
Norm M said:
I have rebuilt Zeniths, Tillotson Xs and F1Bs, and Marvel Schebler carbs; in my opinion the Marvel out performs the other carbs for the Model A.
If you are considering installing a Mitchell overdrive, they offer a 36% unit which would probably work well with your 411 rear. Give Steve Mitchell a call, I sure he will be more than happy to help you.
Norm
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What are your observations on the F1B Tilly? There are a lot of them floating around out there but nobody has much to say about them. Thanks for any info. :)
 
Sunny the Model A said:
Sidenote, I am going to put a mitchell 26 o/d in it, but I can't afford it at the moment, so any info from y'all is much appreciated.
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Sunny, If you think you will have the coinage to afford a Mitchell in 6-8 months, you might think about ordering one now. The Mitchell's are about that far out on orders. Call Steve or Cyndi, they will give you the skinny.
 
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