750 cfm troubles

ok i have sbc 383 with a edelbrock 750, summit 1105 cam, world products sportsman 2 heads, pertronics hei, 2.73 gears and a th350 trans in my 70 nova. I have a bad part/mid throttle stumble and the engine pops thru the carb. The car pulls like crazy thru 6000rpm at WOT. At mid range rpms and part throttle she stumbles,loads up and pops. The carb is still at factory settings except for the pump linkage, which I have set for the longest stroke. I have moved the timing from 8 to 12 BTDC and back again. any help would be great.

thanks

Edelbrock has a great chart on their website for diagnosing and calibrating their carbs, might want to check it out. My experience with the Edelbrock carb's is they will hold their tune very well, but the initial calibration to get idle, part throttle, and WOT all dialed in correctly.... Also, most all the online parts stores sell the calibration kit for the carbs...