Hello Panic, I didn't seem to understand what you meant by cut-in point for the power valve? I think to the best of my knowledge, that I have the main jet set as far out as possible, I have really good vacuum, ill have to see if the vacuum advance is working correctly on my distributor. I know for a fact my fuel is leaking back down the fuel pump. That ethanol just eats away at the rubber parts, I can see the fuel go down in the clear fuel filter. I cant imagine how it makes its way back up to the gas tank, but it has to go somewhere.
Your experimenting has pretty much proved what some of us suspected from the beginning. The carburetor in question does not supply sufficient air nor fuel to get the best performance from the engine, nor does it meter the fuel properly across the range of operation from idle to power production to light throttle cruise. The carburetor provides barely adequate performance- - - - -not optimum. It's better than a worn out, dirty carb, but not by much. Over time, it will probably deliver sub-part fuel economy as well. You might- - - -but probably won't be able to improve things by installing a bigger venturi and opening up the main metering system to flow more fuel than the wide open main jet can supply. Doing that properly will require more equipment and a more thorough understanding of carburetor theory and modification than you currently have at your disposal. Jerry
The murder victim was drowned in a bathtub full of Rice Krispies and milk. The coroner blamed the crime on a cereal killer!
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
Im glad you were able to arrive to a certain conclusion with my experimenting with this Carburetor, though I do not wholly agree with your assertion. My initial goal was not to surmise if the UN2's performance was equal to or greater than that of the Rochester, but if it helped you to come to that initial conclusion, then that is a good thing, though it is still a bit too early to conclude that as of yet. There are still other avenues I can explore before we have the final word. As I mentioned from the beginning, my purpose for trying this carburetor out was to gauge its quality, and craftsmanship, and also its utility with our stovebolt engines, not necessarily its performance. Seeing as how no one on stovebolt.com had tried this carburetor out, I believe this experience has been favorable, and shines a good light on this carburetor. Also, something to consider, one does not always chose a carburetor depending only on all out performance. If that were the case, we would all be running Fuel Injection, which gives the optimum air/fuel mixture for performance, driveability and fuel economy. For many reasons we continue to run Carburetors, be it Rochesters, Carters, Zeniths, Daytonas, etc. My sole experimenting as of yet has been on my 261 c.i engine, but there are still many other engines one could try this carburetor on, for example the 216 ci or the 235 ci, maybe even the 250 ci. and the 292 ci. Also,one always has the option of running a dual carburetor setup or even a triple carburetor setup, which I think this carburetor would lend itself well to, if performance is what your after. I believe that so far the UN2 has proven to be a good alternative if one wants good performance, great drivability, and quality of craftsmanship, but everyone can decide for themselves and come to their own conclusion on that.
2/18/2020 Update: I called the Dayton Company and talked with Ron, one of their older tech guys. Very patient, went through all the troubleshooting I can do to fix my low power problem. According to him, they test these carbs on their 320 ci Hercules engine. The UN2 is good for up to 275 ci with no problems. So it seems to be a problem on my end which I hope to remedy. One of the main things that I hand not changed was the timing. I don't know why it slipped my mind, but im sure that will be a major contributing factor. Ill do what conventional knowledge says and advance as far as I can before I hear pinging. Any other tips will be appreciated.
I don't make them, that's what they told me. They're the professionals. It would be good to ask someone that has a 2 carb setup how it runs. How he tuned it and if he's content with it. I've seen it done many a time. Im not an expert, but ive seen Chevy 350's with 500 cfm 600 cfm 700 cfm up to 900 cfm carbs. It doesn't mean its specifically tailored to that specific engine, but im sure its close enough. I have a friend with a 366 Chevy engine (I had never heard of it either) with 2 progressively connected 600cfm carbs, he says he wants to go to a single carb 900+cfm Carb because though it does give him crazy performance, the in town usability suffers, that's a 300cfm difference but im sure its going to run great, I doubt anybody would criticize him on not having the exact perfect carb for his engine . 235 and a 261 engines are not precision modern machines (though in their time they were), im sure Rochesters and these UN2 units can be adjusted to give adequate smooth performance as ive seen done with mine (and im still tinkering with it). I cant come to grips with some peoples opinion that the carb has to be perfect to that engine. In that case, there would be no aftermarket carburetor dealers, Edelbrock, Holley, Demon, and who knows how many others.
I'm a little late coming into the conversation, this carb. (UN2), is produced primarily for the S. American market. A lot of old cars which the original Rochester "B" will work on are there. Cuba has them on everything! Like the song by Jackson Brown " you can see a Soviet transmission in a Chevrolet". I'm a Rochester model "B" fan(atic), the reason that ClassicsR4Me is having trouble with the gas drain is one of 3 reasons: leak in fuel bowl to air horn gaskt., fuel line leak at carb or the Throttle body shaft. These old carbs can only be rebuilt so many times and beginners have a tendency to warp the air horn. A whole big bunch of thanks to Classics R4Me, great job and very attentive to his testing and follow up.
Currently making 1954 3100 better than new and Genetics
Thank you for the information Doc. Its good to know these carbs are widely used and working in many applications. Your correct about my Rochester, it looks to have been rebuilt a few times and though it gave me very good service, I just wanted to try a new carb to see how it would perform. Im still fiddling with it, im sure I can get a little more performance from it yet.
I've been following this and have wondered "What would the original owner of my '48 do?" He'd probably slap on the UN2, if needed, and go feed the cows. Picture shows where my '48 grew up on the Rocky Mountain Front.
28 Years of Daily Driving. With a '61 261, 848 head, Rochester Monojet carb, SM420 4-speed, 4.10 rear, dual reservoir MC, Bendix up front, 235/85R16 tires, 12-volt w/alternator, electric wipers and a modern radio in the glove box.