SM Head...... ootb vs reworked valve seats(with very small back cut on both valves) and minor bowl blend......
4.00 bore, 28” test pressure, no tube on exhaust.
A-ootb
B-reworked
Intake-
Lift———A/B
.100— 61/65
.200— 120/126
.300— 177/180
.400— 221/230
.450— 231/246
.500— 240/256
.550— 250/267
.600— 250/262
.650— 251/261
.700— 253/261
Exhaust-
Lift———A/B
.100— 49/50
.200— 97/101
.300— 134/139
.400— 154/169
.450— 160/174
.500— 164/178
.550— 166/179
.600— 168/180
.650— 168/181
.700— 168/182
It’s a decent gain considering it’s maybe a 1cc increase in runner volume.
