What carb and intake for 5.9 Magnum?

[Idaho]

Here's a couple more articles. The testing was done on big block chevys so not totally applicable but their comments suggest the results can be generalized.

Other research determines the non-RPM performer is definitely out as a candidate. With upgraded heads and cam it would be a bottleneck.

Edelbrock obviously knows what they've got as the RPM carries the highest price tag, with an extra $30 or so for the air gap version. In cold weather the air gap has poor driveability until warmed up.

The final test verified our longstanding belief: The RPM Air-Gap is the single best all-around street/strip manifold you can buy. We've seen it time and again on engines of various makes, and while we have witnessed applications too wild for an Air-Gap, we've never seen one too mild. On fairly radical pump-gas engines, the Air-Gap usually delivers enough torque increase to more than make up for a slight loss of horsepower as compared to, say, a Victor Jr. single-plane. Flowmaster recently tested a GM ZZ572/620 crate engine, replacing the factory single-plane with an Air-Gap 2-R; the engine gained 65 lb-ft at 2,000 rpm and only gave up 14 hp at peak! The effect on average from 2,000 to 6,000 rpm was minimal—it just skewed the power curve much lower.

Read more: http://www.hotrod.com/techarticles/113_0407_best_induction_combo/viewall.html#ixzz1oBHcEA2v

Conclusions
Edelbrock claims a cooler inlet charge with the Air-Gap design, which uses an open valley beneath the plenum and freestanding runners. We did not data-log temps, but we suspect the cooling effect doesn't make a lot of difference in the dyno room, where the engine is not very hot to begin with, and there's plenty of airflow across each intake. We think there are minor differences in the plenum volume or port shapes that create small power gains with the Air-Gap. But we could be wrong.

Bottom Line
The Air-Gap is always a top performer, and it looks cooler, but you can save the $24 by purchasing the regular RPM, and you won't go wrong.

Read more: http://www.hotrod.com/techarticles/..._not_edelbrocks_rpm_vs_air_gap/#ixzz1oBImNrLT