Too much static compression can definitely hurt horsepower in most engines and especially in a Hemi. Horsepower potential is dependant on dynamic compression, not static compression. Too much static compression coupled with "short" cam timing will result in a engine that will not produce the desired HP. The cam timing must be matched to the static copmpression ratio to keep the dynamic compression within a workable range. You cannot make acceptable HP with a huge duration cam in a low compression motor, nor with a small duration cam in a high compression motor.

A 426 style Hemi also has potential trouble with adequate flame travel and flow through the cylinder during the overlap period. Too tall of a dome will inhibit the flame travel and/or detract from the "chamber cleaning" during the overlap period. The original prostock motors used 12.5 compression because anything greater caused these inherent problems. The 99 hemi uses a flatter chamber and dome to combat these problems, as well as offering a shorter and lighter piston compression height. Current Prostock racers start with 17 + compression, dyno the motor, work on flame travel until colorization/HP is optimized (usually around 15 to 15.5 Static compression). Large cube wedge style motors do not suffer from these flame travel problems because their dome is very short or non-existent. Flame travel will always take precedence over static compression ratio.