We found the Magnum R/T heads to be an excellent replacement piece box-stock with outstanding possibilities. In milder combinations, simply blending the bowls and bolting them on will provide a dramatic improvement in port flow over any production small-block head with minimal effort. Ported as illustrated here, the R/T heads will support outputs into the mid-500hp range in larger displacement engines. We achieved 270 cfm of intake airflow, which compares favorably with the better CNC-ported aluminum heads offered for competitive makes of engines. Is this the limit? We found all that air with the production Mopar valve job and stock production valves. Valve mods including a back-cut intake and radiused-margin exhaust valves would undoubtedly pick up the numbers at lower lifts, as would a competition valve job. Further flow enhancements could potentially be achieved with chamber mods, including a de-shrouding cut, which would be performed as part of the high-performance seat machining. Given the port layout, we consider the Magnum R/T as kind of a baby W-2, having a terrific port configuration that's just made to support high flow, while retaining the convenience of a bolt-on replacement.

Superflow 600 Flowbench
Tested By Steve Dulcich

Table 1
Intake Airflow
Cubic Feet Per Minute @ 28-Inch Pressure Drop
LiftStockMod1Mod2Mod3Mod4Mod5Mod6
.050"3132.53434353536
.100"60.5626667666666
.200"123125128128128129128
.300"173177179178180178178
.400"205217218219224220222
.500"219238242240243244246
.600"223246250252258258264
.700"220242253261266263271

Legend

  • Stock As delivered by Mopar Performance; stock valves
  • Mod 1 Blended as-cast bowls to bottom cut of valve job
  • Mod 2 Streamline guide boss
  • Mod 3 Blend short side turn from runner floor to bottom cut of valve job
  • Mod 4 Cut pushrod intrusion to .040-inch thickness
  • Mod 5 Blend and straighten runner
  • Mod 6 Polish port

Table 2
Exhaust Airflow
Cubic Feet Per Minute @ 28-Inch Pressure Drop
LiftStockMod1Mod2Mod3Mod4Mod5
.050"303029.5313031
.100"565558.2595859
.200"107108110110110116
.300"150149150150151155
.400"170173176176178179
.500"177183187188198204
.600"180187192193207213
.700"NR189195196211217
PIPE*194218221223234238

Legend

  • Stock As delivered by Mopar Performance; stock valves
  • Mod 1 Blend as-cast bowl to bottom cut of valve job
  • Mod 2 Streamline guide boss
  • Mod 3 Blend short side turn from runner floor to bottom cut of valve job
  • Mod 4 Blend and straighten runner
  • Mod 5 Polish port
  • Peak flow with flow pipe attached to runner exit