Head Flow Comparison Flow Numbers are from MID-AMerica Performance and my "Zoltan" ported "C" heads.

All flow values are for 28" - H20.

Some intresting Formulas:
HorsePower (per Cylinder @ air flow) = 0.43 * (Head flow CFM @ 10in-h20)
or 3.44 * CFM for an 8-cylinder engine.

Example: At .500 lift a stock "C" head flows 250 cfm at 28" of H2O. You must convert this to 10" of H2O. Click HERE to find the correct multiplier. The potential HP is (.598*250) = 149.5 * 3.44 = 514 HP

Another formula shows at what RPM peak HP should occur based on engine displacement
This lets you select the proper camshaft duration to match to the heads airflow and engine size
Formula: Peak HP RPM = [2000 / Engine CID (per Cylinder)] * Headflow CFM @ 10in-h20
Or HP RPM = [16000 / CID (for 8 cylinders)] * CFM
Example: Same head as above on 455 engine. HP RPM = [16000 / 455] * 149.5 = 5257 RPM

---

Stock Olds Big Block 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 28" of water.

All flow numbers are stated in CFM (Cubic Feet Per Minute).

---

BIG BLOCK INTAKE PORTS (STOCK)

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

    .100   84   85    85    92    89    92    91    87    81    85   
    .200  159  159   162   164   156   165   158   159   144   157
    .300  208  209   211   207   215   210   205   209   206   209
    .400  233  232   233   228   243   227   225   232   223   224
    .450  243  244   244   233   246   234   231   239   225   231
    .500  250  250   250   239   250   240   236   243   227   236
    .550  254  253   253   243   252   242   237   245   227   237
    .600  259  258   259   245   253   244   239   248   227   239
      

BIG BLOCK EXHAUST PORTS (STOCK)

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

    .100    54   50    49    50    48   49    47    50    49    47
    .200   101   99    99    98    92   99    96    98    89    94  
    .300   135  133   133   133   127  129   129   131   121   126
    .400   151  146   145   147   147  144   145   147   125   144
    .450   154  152   151   153   153  148   151   153   126   149
    .500   160  158   158   157   158  154   156   158   126   156
    .550   163  161   160   162   162  158   158   162   127   150
    .600   169  163   162   166   166  162   161   165   127   161

---

My ZOLTAN ported "C" heads.

Heads are from a 1968 400, Prior to Zoltan work includes: SI stainless steel 2.072 intake valve, 1.71 exhaust valve, aluminum filled crossovers, raised exhaust port exit and removed EGR bump. Final porting and polishing done by Zoltan's Flowbench 604-859-6423. The stock flow is what my "C" heads flowed before they were equalized and finish ported by Zoltan but I did do a bit of work to them before Zoltan worked on them. Zoltan mainly cleaned up the ports, bowls, and slightly raised intake port and equalized the flow. The flow numbers differ from the stock flow numbers above but these are the actual numbers from my flow sheet.

		PRIOR TO	ZOLTAN		PRIOR TO		ZOLTAN
		ZOLTAN		PORTED		ZOLTAN			PORTED
Valve Lift	INTAKE		INTAKE		EXHAUST		EXHAUST
	
    .100      71		 78		 55			 61    
    .200     137		149		103			115
    .300     180		199		138			152
    .400     222		236		156			178
    .500     243		259		170			209
    .600     256		279		186			218

---

HOMEPAGE    CAR'S STORY    BURNOUTS    VIDEOS
RACE GAS INFO    EDELBROCK HEADS    ROCKET LINKS