[storm9c1]

I still think you might be able to gain 1-2" using full manifold vacuum on the distributor and retuning the carb for that. But every engine is different. It'd be more of an experiment than a promise. Keep in mind a few things if you switch this. 1) You have to make the switch with the engine warmed up to see correct results. 2) You will have to lower the idle at the carb with the stop screw. 3) You should retune the carb with a vacuum gauge after making these changes. Otherwise it will seem like you have no gain and perhaps even develop a stumble without that type of retune. It does change the vacuum profile of the engine. Screw the debates about which is better (ported or vacuum), the engine profile tells you this. Stock profiles might like one type. Radical profiles might like another. It's a trial and error process. Nobody can tell you which is right or wrong (which is why this is so heavily debated). But your engine can tell you if you listen.

I'd also be tempted to try a vacuum canister next. Not uncommon to need one with a radical cam. Or last resort, as discussed, change the cam.