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Old 09-29-2011, 11:41 AM
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We must be careful when comparing cylinder heads for purchase because we don't have a standard testing procedure. We don't know, in most cases, the size of the fixture the manufacturer is using, the distance from the cylinder block to the valve seats, the number of angles they used on the valves and seats, whether or not they used undercut valve stems, dry flow or wet flow, what equipment was used to do the flow tests, what the ambient conditions were at the time of test and on and on. RHS shows some good figures of their heads, and they should show good because they use a 4.200" barrel to test small block Chevy heads. If you compare their flow with another mfg who uses a 4.030" barrel, the larger barrel will flow more CFM every time and that's what sells heads to Ricky Racer.

Here's a nice little article that I found after a little surfing....
http://www.flowspeed.com/cfm-numbers.htm
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