Zenith and Tillotson

[gilitos]

I installed a NOS Tillotson X a few months ago while waiting for some parts for my Zenith 1....I had bought the Tillotson in its original box, and it had never been installed before. Seemed to run fine, nothing special. Yesterday I replaced it with the Zenith. The car seems smoother and more powerful, with better throttle response. Subtle differences but real. Is this just a difference between two individual carburetors, or do any of you share this experience?

[Frank Nemo]

When I acquired my 1930 Sport Coupe it had a Tillotson and ran very nicely. While striving for authenticity I traded the Tilly for a Zenith that had been rebuilt by a man with a very fine reputation as a carb rebuilder. In fact he has written a book on rebuilding Zenith carbs. After replacing the Tilly with the Zenith the car did not run nearly as smoothly or with the same power level. With all kinds of adjustments to the Zenith I never did get to run as well as it did with the Tilly.

I bought a second Tilly, put it on the car and it ran beautifully again. My conclusion from my own experience and reading many Fordbarn and Ahooga threads on this subject is that for some reason some cars run better with a Tilly and others run better with a Zenith.

Yours apparently likes the Zenith. That new Tilly in the original box is worth some money. One recently sold on -bay for over $150.00!

[TinCup]

I find that the Tillotson idles better than the Zenith. It also seems to get better gas mileage. Nothing significant but I notice it when I run the tilly vs the Zenith. I also have a Tlllotson F1-B which looks just like a Zenith and it runs and idles well also.

[HoarseWhisperer]

My Roadster was equipped with a Tilly XF which always ran great with little adjustment or maintenance.

The Tilly finally developed an whistling vacuum leak, which I never took the trouble to isolate (throttle shaft, intake, upper/lower casting warpage), because I wanted to run Zenith for orginality reasons.

I've run three Zeniths since, managing to rebuild them to run correctly, which they do for a time. However, they seem to require more frequent maintenance than the Tilly (or could it be the increasing use of that "evil" ethanol?).

[Richard Lorenz]

The Tillotson X should be better than the Zenith. The jetting is a more modern design, and the air flow resistance of the Tilly is slightly less than that of the Zenith. My experience with both agrees with the above. You do have to watch out for warpage, which you are aware of.

[mrtexas]

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Originally Posted by Richard Lorenz

The Tillotson X should be better than the Zenith. The jetting is a more modern design, and the air flow resistance of the Tilly is slightly less than that of the Zenith. My experience with both agrees with the above. You do have to watch out for warpage, which you are aware of.

May be a more modern design but I think both Zenith and Tilly were designed in the 20s. Tilly is a much simpler design which I think is it's advantage. I've restored 25 or so Tilly's.

[Kevin in NJ]

There has been a lot of back and forth on the carbs.

The problem is the huge variation in the rebuilding of the engines. In particular if you think about the very very subtle variations in problems you can get from valve systems being put together.

So to accurately compare the carbs you need to run on engines that are setup properly.

To say that one carb worked better than another on an engine you need to fully qualify by adding every detail on what was done to the engines breathing. Bill with his reground cam off by 1 degree (but does not know it) might find different results from Fred who just put a nice used cam in the engine. I will not even get into understanding valve gap set up adjusted for the types of metals in the valves.

From many years of talking to people and reading on the boards, a properly rebuilt Tilly can work as good as the original Zenith. I personally have seen a lot more Tilly's leaking. The single bolt original is much simpler to deal with when you have a problem. The only problem is you will probably never have a problem with a properly rebuilt original (we shall see what new gas brings us).

The key is properly rebuilt. A properly rebuilt engine, a properly rebuilt carb as it is a system that works together.