My new CB Perf. CNC ported heads with 44 in. and 37.5 exhaust valves are at Darren Gurrola's shop in California for some work, so Darren hooked them up with his flow bench and got the following CFM (cubic feet per minute) numbers at 28" of water test pressure:
Lift INTAKE EXHAUST
.050 29 24.6
.100 48.5 46.5
.150 67.8 66.6
.200 86.7 84.7
.250 103.2 101
.300 122 118
.350 136 128
.400 150 130
.450 166 130
.500 182 130
.550 195 131
.600 206 132
.650 213 135
.700 219 135
The lower exhaust flow is misleading as exhaust gas pressure and velocity will be somewhat different from test pressures. A rule of thumb is that a properly set up and tuned engine can generate a little over 1 BHP per CFM intake flow, e.g., if the cam and valve train creates an intake valve lift of .550" with commensurate duration and proper valve timing then the engine would probably produce between 205 and 215 BHP.
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