ive got a 460BBC with a xe268 cam,rpm intake,closed oval heads and double pumper carb that was a 650 unit.i modified the carb with proforms mainbody with the supplied jets 72/84 and the engine sounded like it had a much larger cam.i had planned to go back to my 750 VS carb because the double pumper was to be used on my smallblock motor.i noticed that the throttle was more sensitive,but it wasnt until i drove it that i noticed that the engine wasnt choppy as it had been.but there is one thing thats happening is its leaning out at wide open throttle.anyone ever convert a vacsec carb with a primary metering block and block the power valve??????