A couple thoughts/ questions:
1) To HRL’s comment about the power valve. Doesn’t a bottomed-out idle screw equate to a blocked idle circuit? Thus Pre-68 Dave’s suggestion of wrong gasket is worth a look? (Not being a smart-arse, just trying to learn something).
2) I also fully understand the it about throttle opening nullifying the idle circuit. But I have my doubts about 500 rpm being a number at which that is the case. Unless some other engine condition is suppressing idle speed (timing, some sort of miss, etc)…I’m not convinced 500 rpm would expose the transfer circuit.
Something that would be of NDKid’s benefit, would be to pull the carb in its current “500 rpm” state, without making any other changes, and just see if the transfer slot is exposed.
