I have two 94's on my flathead and I am using straight, non-progressive linkage. It seems to work okay but I am wondering if anyone has experience with progressive linkage for twin carbs? What brands and how well do you like them. Better than straight linkage?
I've got the same setup as you. Am going to try progressive as soon as I get another carburetor to rebuild. Don't want to mess up the matching pair. Will be blanking out the idle circuits in the base and using a 3 1/2 power valve on it. Also, you have to use an intake with a common plenium to have it work. Mine's a close Offenhauser one. Butch
I have never done progressive in little carbs but I have done it with the large base Rochester and with 350 Holley carbs. I loved it, hut like I said I was using larger carbs. Here is something that both of you should think about, before blocking the idle circuit you need to make sure that your butterflies are shutting completely off. If you are not getting your carb completely closed you are better off to leave the idle circuit intact. You donot need the extra going into your intake. Carbs that ar dedicated secondary carbs usually have thicker blades that are shaped differently so that they close the carb completely off. A standard carb will not be able to shup the air off completely.
As stated, It is very important to get a good seal on the secondary carb. You will have trouble tuning without a good seal. Replace the the throttle blades with ones made for secondarys. You will need to massage them to seal in the throttle body bores. Speedway and Vintage Speed have the secondary blades. The Fordbarn opinions run about 90% against running progressive on dual carb set ups. If you post this question over there, be prepared for some strong opinions.
The problem is the distance from the primary carb to the end cylinders though the middle of the intake. You may run into a miss-fire or lean condition. I hold the secondary carb up to a light to see if it is fully sealed after installing the thick plates and oversize shafts (due to leaks).
Why? I have run 2 97s on a flat head and a Studebaker 259. Both with straight linkage. If they are synchronized they should do just fine. My Stude engine was running when I got it but when I checked it, it was way out of sync. I think progressive linkage on 2 twos creates more potential problems that they ever cure. On straight linkage each carb supplies 1/2 of the need fuel. Unless you have a leak in your manifold you will not lean out the fuel/air ratio due to a longer run or else a 2bbl on a V8 engine would have a problem.
As others have pointed out, there is no good reason to run progressive linkage on a two-carb flathead manifold, as the result will most likely be uneven mixture distribution, because of design. If mileage is your concern, I doubt you will see any difference in normal driving, at least I haven't. Setting up dual carbs exactly the same with straight linkage will give the best overall results on flathead Ford dual carb intakes, IMO. A four-barrel intake would be the best intake to run progressive 2-barrel carbs.
I did it with 2 94s on an Offenhauser regular manifold. Got secondary throttle body, power valve blockoff, and progressive linkage from Charlie Price at Vintage Speed in Florida. Worked out well. Seems to have a better throttle roll-out and more low end torque than my other setup with 2 Stromberg 48s on straight linkage.
If working with three carbs, instead of expensive new bases, I did this on two much different three two set ups. Make the two end carbs the same jet and PV wise, and leave the idle mixture screws open 1/8 turn. Start and warm the engine, then turn all six screws to get the smoothest idle. Cheap and easy.
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