[turbobill]

GMC V6's are not immune from the benefits of increased airflow at engine speeds greater than torque peak RPM.

While they may ultimately not respond (percentage wise) like some other engines, it seems most report gains with the 500 Holley and a dual exhaust. I tend to think that the restrictive factory carburetion was more for economy and a reduction in HP for longevity under a wide range of users than anything else. The factory single exhaust was the lowest cost solution and worked ok with the small factory carbs.

A less restrictive exhaust tends to lower EGT's at the exhaust valve, exhaust port and manifold too.

While calculations show 500 CFM to be overkill on a 305 running at factory designed engine speeds, as with many things, calculations do not represent real world results. More than likely, the same engine with a 500 CFM carb will make more horsepower than the same engine with a 350 CFM carb, or the factory carb.

And, as far as Holley carbs go, the 2 bbls and 4 bbls are rated using different pressure drops across the carb, so comparisons between the two isn't really an apples to apples comparison. And I have no idea what pressure drop either Carter or Rochester may have used to rate their carburetors, so comparison between the manufacturers is just about impossible.