The US 2V heads on one of our 351Cs flowed 235 @ .550 intake and 220 @ .550 on the exhaust. These were home ported heads using 4V valves, mostly short turn and bowl work. The intake was at 257 @ .400 - the floor in a 2V head is really flat and at about .450 the air has a hard time making the turn into the pocket. Stick with a 2V valve size and as big a radius on the short turn as possible. You'll find that the 2V are pretty much all done by .5 or .550. With a 226/230 Crane cam and 9.3:1, the engine puts out about 380HP.

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1967 Falcon 4 door 351C - Owner built, owner abused.
70 Mustang 351C / 06 Ranger, 04 SuperCrew parts hauler