Stock Olds 400, 425, and 455ci Cylinder Head Flow Tables

Stock Olds 400, 425, and 455ci Cylinder Head Flow Tables

All valve sizes used for baseline flows on intakes were 2.071", except on the "J" head which had a 2.00" intake. All exhaust valves were 1.625". All flow tests were conducted at 25" of water. All flow numbers are stated in CFM (Cubic Feet Per Minute).

BIG BLOCK INTAKE PORTS

                           Cylinder Head Type
              
Valve Lift  A  B  C     D      E      F   G & Ga  H     J      Ka

     .100       80    87     84     87     86    82    76     80  
     .200      153   155    147    156    149   150   136    148
     .300      199   195    203    198    193   197   194    197
     .400      220   215    229    214    212   219   210    211
     .450      230   220    232    221    218   225   212    218
     .500      236   225    236    226    223   229   214    223
     .550      239   229    238    228    224   231   214    224
     .600      244   231    239    230    225   234   214    225
    

BIG BLOCK EXHAUST PORTS

                            Cylinder Head Type
                
Valve Lift  A  B   C     D     E      F   G&Ga     H    J     Ka 

   .100          46    47     45    46     44    47    46     44
   .200          93    92     87    93     91    92    84     89 
   .300         125   125    120   122    122   124   114    119
   .400         137   139    139   136    137   139   118    136
   .450         142   144    144   140    142   144   119    141
   .500         149   148    149   145    147   149   119    147
   .550         151   153    153   149    149   153   120    150
   .600         153   157    157   153    152   156   120    152