Quote:
Originally Posted by Peter J
Steve, I've been away from Model A's for about 40 yrs. When and why was a "new" carb. made? Exclusively for A's and B's or also for tractors etc. I've never seen one before.
Pete
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Pete,
I really don't know much about this for sure. My impression is that Zenith never really quit making carbs, although Ford quit using their product. The 13922 was apparently used in a wide variety of variations and applications. One key modification that became a standard requirement in the 30's was use of an air filter; this required that the gas bowl be vented, not to the atmosphere, but to the air intake throat of the carb. Otherwise, the inevitable pressure drop due to air filter resistance would cause the greater (atmospheric) pressure in the bowl to push out too much gas. The improved bowl/float design reducing stalling on sudden stops seems to me to be an even more wonderful advance.
I am attaching another pdf by a Rick Botti that I found during my Google searching. This has some more interesting lore, but I have no idea of the date, authenticity, or original publication venue. It sounds like it was in some club's newsletter. Judging by the font and layout, it might even be from the Restorer or Model A News. My inquiry to Frank Witkowski, an apparent supplier, at the "bellatlantic" email address listed bounced back.
Another thing that has wondered me about the carb is whether it was designed for use with a fuel pump, another advancement that became standard in the 30's. The Botti pdf mentions experimenting with fuel pump pressures and finding that 1.5 - 2 lb pressure was good. He said that less than 1.5 starved it at high speeds. I've had my car up to 60 mph with this carb on it, which is good enough for me. I guess the fact that we continue to hear only positive, often rave, reviews by Model A'ers who have used it tells-the-tale. On the other hand, I have seen it disparaged as the "forklift" carb by folks who I assume are restoration purists who likely have not used.
Other knocks of its design I recall from earlier threads include the loss of enrichment adjustment from inside the car (the choke rod only chokes). It sounds from the earlier pdf like this was finessed by the "economizer" feature. Also, there was something about the design of the enrichment valve being more prone to blockage by crud in the gas, which brings me back to wondering about fuel pumps AND the gas filters they enable. BUT, again, it's hard to argue with a bunch of satisfied owners.
I've only got a few 10 mile trips on mine, but it seems good so far. My only objection would be that it's noisier than my original Zenith-1. I've taken off my heat shield and most of my ugly insulation on the fuel line, etc., and no vapor lock issues so far.
Steve