My Procharged 353 uses a 242/254 @ .050 cam, 114 LSA. It was designed and spec'd for my engine combination by a guy who at that time nearly exclusively built Procharged engines, now he's doing turbos too.

My engine has a very healthy sounding idle (although somewhat muzzled running through large cased Magnaflows)... and it still makes plenty of power. Engine has about 2 psi of boost at 2000rpm at WOT with the Procharger and it ramps in pretty quick from there. Many guys told me my cam was just too big (based on more "oldschool" thinking about boost and cams) but quickly changed their mind when I took them for a ride.

Too small of a cam with forced induction can hurt the top end efficiency of the overall combination too as the valves just aren't open long enough.

Since you mentioned mileage... I get 18-19 mpg at 80-85 mph, and 22-24 mpg at 65mph with my combination. Car is tuned to be in the 50's for timing and 15.5:1 AFR at freeway speeds. Car is geared so that the cam is happy in 5th at around 55mph, any lower RPM than that and it starts to buck a bit. I geared the car to have the cruise RPM just over where the cam "cleans up."



I also helped build and tuned a 427 small block Ford with an F1R; 847hp on 91 octane pump gas and the cam was pretty stout too, pretty nasty idle. I seem to remember the cam being 25X/26X @ .050 with mid .600's on the lift. However the engine had an awesome torque curve from 4000-6700, not at all what you would expect from a centrifugal and especially with that big of a cam. It would have made more power if we spun it to 7200 but we ran out of injector. Need to change injectors and go to the dyno again.

Bigger cams are starting to be used more often with great success on turbo combinations as well. It used to be that everyone ran short duration no-overlap cams with small A/R exhaust housings for quick spoolup. Now, you see more and more people running larger cams coupled with larger than usual A/R turbine housings and these combos are working very well in the real world. The larger cam makes more HP off-boost than a small no-overlap short duration cam. The larger cam makes more off-boost HP, and more HP means more exhaust volume to spool up the turbos; you still get quick spool as you do with a pipsqueak cam and small A/R housings but the bigger cam and bigger A/R housing makes way more power up top because of the less restrictive larger turbine housings... and they have some "sound" at idle.

Again, it's all in the entire combination. Everything must be accounted for and planned out... but if you do, you can have a little lope at idle with your boost and things will run great.