I hate to say this because,,,
Are you sure your choke linkage isn't working backward?
^^^^^^ this is a good question & worth checking ( after your comment about running with the choke on --- check your set-up).
I'm in same train of thought as everyone else here, not enough carb. I ran a pair of Langdon's progressive H-Ws on my 261 and worked great but began having trouble with them and went with a pair of Stromberg BXOV-2s wow what an improvement. Last hop up was on my 3600 flatbed running a '54 bored out 235, decided this Clifford 4 barrel intake had been hanging on the wall way too long so picked up a 390 cfm Holley from Summit, really woke the truck up better than any dual set up I've owned. Best of luck
^^^^^^^ This is what I'm running ....... (Offy intake, Holley 4bbl 390cfm carb, using stock exhaust manifold) .. on my 250 I-6, stock engine, single exh. Carb installed (new) right out of the box , runs great , just FYI
jim
