Gabriel - that is an interesting answer, that really doesn't tell us much, other than you can order parts from Daytona at this time; how about elsewhere.
I have no issue with adjustable main jets, and consider them a bonus; however, they are NOT the major criteria in selecting a replacement carburetor. Internal size IS the major criteria, which is one of the issues to which Panic was referring in his post. One really great application of the adjustable main metering jet is the ability to temporarily retune an engine on a trip. As an example, if I were to leave Missouri (elevation where I live approximately 800 feet) and make a trip to Denver (elevation about 5500 feet).
When a customer asks us for a replacement carburetor; we have a list of questions.
(1) flange size (Daytona covers this)
(2) engine displacement and engine modification. These are critical in selecting the proper carburetor, as they give us information to determine internal venturi size, which is what determines the airflow characteristics of the carburetor. If it is determined that a specific engine requires a 24 mm venturi, and one installs a carburetor with a 27 mm venturi; one can adjust the adjustable main jet from all the way in to taking it out and putting in one's pocket, and the engine will always be sluggish at lower RPM. Conversely, if the engine requires a 27 mm venturi, and a carburetor is selected with a 24 mm venturi, then the engine is going to be sluggish at higher RPM, and in effect, the venturi will be a rev limiter.
(3) once the proper venturi is selected, then the adjustable main metering jet is useful to "tweak" the mixture for the volumetric efficiency of the given engine; but it will NOT compensate for using the wrong size venturi. Generally speaking, our customers never need to adjust the adjustable jet (if the carb we sell has one) more than plus/minus 1/4 turn (generally less) from the standard setting. And other tuning components are useful as well. As an example, Carter offers at least 5 different vacuum springs to help tweak the mixture for different engine vacuum profiles. This is not possible with a carburetor with an adjustable main jet UNLESS the adjustment is connected to a dial on the dash and may be adjusted "on the fly" by the driver.
(4) next question is cost versus performance. Not everyone wants to pay for good performance and reliability (one reason the Rochester B's are still somewhat popular). The Daytona carburetor certainly fits the "less expensive" criteria.
(5) we also ask about the terrain traveled by the customer, as there are some less expensive carburetors that may be used successfully if one drives in an area that is virtually flat.
But the key for you is that if you are totally happy with your purchase 5 years from now, then that becomes the ultimate criteria.
Jon.
Last edited by carbking; 01/10/2020 5:05 PM. Reason: Typo
