5 We wanted to see how well a pair of these heads performed when placed in a non-factory type of condition. So, to step up the pressure on the heads, we installed them on a stock 6.1 liter short-block with a carbureted intake using dual 500 cfm Edelbrock carburetors. With our pair of CNC-ported 5.7 heads, and a Mod-Man dual-quad intake manifold, the 6.1/5.7 Hemi amalgamation made 465 horsepower and 423 lb/ft of torque. A stock 6.1 is rated at 425 horsepower, and 420 lb/ft of torque, installing the heads add roughly 40 horsepower, and 423 lb/ft of torque. We suspect that the head's improved flow now needs some additional camshaft to reach their full potential.