I am wondering if the BlueThunder Manifold will improve power and millage on my 57 312 with a Mummert 264 reground cam our should I stick with the stock Manifold?

Power yes, mileage, probably not.

Frank/Rebop

Bristol, In ( by Elkhart) 

At what RPM range will I see the most gains I plan on driving around Town and on Highway not racing unless a scrub ask to see the rear of the 57.

You'd have to ask John Mummert where it'll work best on your combination. John designed the manifold for Blue Thunder. I suspect it'd work best from 3000 up, and as good as a a cast iron manifold from idle to 3000. Manifold seems to work better on more radical combos, and yet it is totally streetable on 292's and 312's. Course it's also lighter (a bunch) and is just plain gorgeous to look at.  

                                                 

Frank/Rebop

Bristol, In ( by Elkhart) 

Isn't the theory that engine modifications help fuel mileage and power so long as displacement is not radically changed and a moderate cam is used?  The trick is keeping your foot out of it.  But that's such a hard thing to do!


Lawrenceville, GA

Charley,

        Your last sentence sums up the mileage issue. And maybe not, If the operating parameters of the engine are changed enough so that normal driving falls outside the most efficient rpms of the engine, the mileage will suffer. Example, radical cams don't work at 1500 rpm cruise. Too large a carb or intake, reduces air/fuel velocity and the mixture becomes less controlled. Both those items will usually help top end horsepower.

    

Frank/Rebop

Bristol, In ( by Elkhart)