A 283 at 6,000 RPM would flow 491 CFM if t was possible to get 100% volumetric efficiency, which can't be done. A more realistic number would be 393 CFM @6,000 which is 80%. Let's round it off and call 400 CFM a reasonable goal to shoot for. With enough carburetion 8K RPM is possible for a well-built 283, but it won't be user-friendly on the street. You'll encounter valve float above 6K unless some sophisticated (translation EXPENSIVE) valve spring and port work is done. A roller cam and a rev kit is almost a necessity to get up into the 7500-8K range with a small block Chevy and keep it together for more than a few seconds. That's about $2500.00 worth of head, cam, and associated hardware work.
I've run "claimer" 350's at the round track to 6,000 RPM on a single Holley #7448 350 CFM 2-barrel- - - - -the manifold vacuum just starts climbing as the RPM goes above the flow capacity of the carburetor. Any good 4-barrel will let the 283 achieve much higher RPM than a 350 can ever see unless the 350 has those expensive tweaks done to it as well. The 3" stroke crankshaft loves to wind up. 350's are like belly buttons and other "holes"- - - -everybody's got one, and some of 'em are pretty stinky! The QJet will simply be the easiest, least troublesome way to get the performance you're looking for, with plenty of volumetric capacity to crowd the top end RPM limit of your cam and lifters every now and then! The tripower will be some nice eye candy at the local show and shine, but the visual "WOW" factor about its only advantage.
Jerry
