<VV> Performance Valve job

[Scott Cable]

Vairheads,
I've been working at night at the local engine shop that is equipped with a Pro-Flow 600 flow bench, and a Superflow dynometer.  I was testing a unmodified World Products SBC head and compared that last night to a barely legal World Products head.  The differences between these heads were that the barely legal head has a 5 angle valve job vs the customary 3 angle.  The valves also were back-cut with a 30 degree angle also.
  The differences in flow were astonishing.  The modified head flowed over 10 percent more than the unmodified head. (275 CFM vs 260 cfm best flow either head) Even more impressive was the flow numbers at the smaller valve lift openings.  The modified head just would not quit.
How this equates to horsepower is:HP=CFM * .2527 * # CYL
Theoreticly the mdoified head would be able to produce 556 HP vs 526HP of the unmodified head.
  So those of you who are going to be doing a valve job, you may want to pay the extra expense of back-cutting the valves, and adding a 15 degree, and 75 degree cut, concentric on the valve guide in the head.  Obviously you need to take your heads to a reputable shop to perform this work. The new seat angles are produced with a cutter, NOT a stone. 
Cheap horsepower.


Scott Cable
Jamestown, ND
s2cable1 at yahoo.com
		
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