Bob Lang's run down on the circle B head is right on target with what I have
learned and heard on this list over the past 10 years. One thing he failed to
mention is that as far as I know the Circle B heads, along with some of the
other heads he mentioned, were only on the later motors (CF motor designation I
think). All of the heads on the CF motors had better breathing properties than
the earlier heads because they used the long runner intakes which, according to
others more knowledgeable than I, provided more torque than the earlier short
runner intake heads. There were other properties of the later heads that
improved upon the earlier versions but they escape me at the moment. The
modifications to the heads on the CF motors (this includes all later heads, not
just the Circle B) supposedly compensated for the reduced power which came as a
result of a reduction in compression (8.5 to 7.75 I think) necessitated by new
emission rules. I have an early motor (CC designation) with
a circle B head from a CF car. This combined with a 9.5/1 compression ratio
considerably improved the power output of my car.
Mike Lunsford, 1970 TR 6
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