This ^^^^^^^^^^^ is one of the things I can actually agree with the Holley tech's on. I've been holding back on posting here again, but there's no way you need a #37/#40 nozzle on a mild engine with a dual plane. That and the potential of needing a big jump in primary jet leads me to believe there's another issue somewhere. Where? I don't know at this point, but you've got to be getting rich on the low end with these mods, and I believe that's what we're trying to clear up at this point? The vacuum secondaries are a completely different issue to me right now. I've actually recommended the 670 on occasion, but I have to wonder, at this point, if you didn't get a bad one?
That carb on your combo, with a proper tune, should need nothing more then slight jet change, and a little lighter secondary spring.......I've run several combo's like yours, over a single plane, with nothing more then a #31 nozzle, one jet up, and a short yellow spring! They were very drivable and ran like a bat out of he!!...
