Quote:
Originally Posted by blaktopr
John, alot of it depends how the port is shaped. One person's "work" can be different from another. This includes how well the mixture exits the valve depending what is happening upstream.
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blaktopr is correct here. Not only about swirl, but the non existence of swirl. What do you think a RA-V head has coming into the cylinder with a straight port? (Chew that one for awhile
)
Recently we got a set of SD heads from a very good head porter. We had extremely good flow, but the CSA of the port was small. So, we sacrificed some flow in order to get that push rod area up to 2.7 square inches up from 2.35 square inches
This gave us peak RPM up to 7200 from 6700 and about 35HP average. What less flow and more HP? What a concept!
Many professional head porters go for shape first and flow second!
Lynn