The cam that pops & steveK are referring to is the Ford Motorsport A341 cam from the 1980s, it was actually a Crane Cams grind, repackaged and sold by Ford. It had really "big" advertised duration specs, 292°/302° with 76° of overlap, the cam looked real big on paper, but was in reality a low rpm pussy cat with a lumpy idle (112° lsa). The advertised duration in this situation was overly optimistic, reality was more like 276°/286° with 57° of overlap.
The Crane Cams H-278-2 camshaft I recommended is most likely the descendent of that cam, with a little bit more modern (next generation?) lobes.
I've seen various explanations why people think so many 351C cams are ground with a 10° duration split, most involving some imagined imbalance of intake flow verses exhaust flow of Ford heads. There is an intellignet reason for that split in duration but it has nothing to do with an imbalance of flow between the intake port and the exhaust port.
There's more than one way to design a camshaft. SEMA & the hot rod industry teaches the LSA & 0.050" Duration method. Those are Harvey Crane's numbers. But another way to design camshafts is based on valve event timing.
If you design a 351C street cam
based on valve events, and your goal is to take advantage of the wide powerband and high rpm the Cleveland head is capable of, then you're going to design the exhaust valve to open at 80° BBDC or earlier, you're going to design the intake valve to close at 70° ABDC or later. This gives the motor its high rpm capabilities. To help low rpm power you're going to minimize overlap with a wide lobe separation angle and you're going to center the overlap event around top dead center as much as possible. To accomplish all of that you'll find the camshaft must have 10° more exhaust duration than intake duration.
Brent and I respectfully disagree on this subject, but I'm going to keep hoping some day the reasoning of this valve event timing will sink in to that Kentuckian head.
Have a good weekend my friend, I hope the wife and baby are doing well.
inebriated son of an Okie