not your everyday carb problem

[Dark Knight]

try bumping up the timing to 10* for a start... part of the prob may be that you have the idle speed turned so high, you're starting to get into the main circuit... try cracking the secondaries open some.. there's a screw underneath the carb..
when you start getting into long duration cams, alot of people drill holes in the primary throttle blades..

however, I think the combination of more timing, bigger gap, and the secondary throttle plates cracked some will fix it.. I never had much of a prob loading up with a 272/282@.050 .640 lift solid roller in my 289 with a 750DP too..

I think with the 351c, you'll need a bigger carb too..