[SCOBRAC]

It really depends on the duration of your cam. Standard FE cams operate well from idle to 5500 rpm and nose over. HP hydraulic cams work well from 2500-6500 rpm. These need more idle to sustain vacuum to keep your fuel flowing, typically 850-1000 rpm. Solid cams are effective into the 9,000 rpm range, but similarly as duration (the amount of time a valve is opening, is open and closing) increases, the amount of idle that is required to sustain it also increases as manifold vacuum decreases

Really big cams need a lot of idle. It isn't uncommon for really big cams to need 1000-1300 rpm to generate enough vacuum to operate. Less than this the vacuum signal at the venturi's is reduced causing irregular idle and lugging. That is an extreme case. Manifold vacuum at idle in those situation may be as low as 3-5 inches.

You didn't mention what your camshaft duration is. Crower doesn't list it on their website general info. If it is a typical performance grind 750-900 rpm is fine.