Besides using a "big cam" for "big heads", what's the secret to figuring out the right cam for your heads? For instance, if the heads have good low-lift flow, or good velocity, or whatever ... How would you choose the right duration, ramps, overlap, and ICL, and be so exact about it that an off-the-shelf cam wouldn't do? (people are always recommending a custom grind over the OtS cams). Is this a secret that only head porters know?

 

I don't think anyone is going to give away a secret to matching camshafts to
an engine profile, but I would imagine the cam matching is relatively simple
in comparison to achieving the head flow numbers.

From what I've read, the valve timing and duration have more to do with 'WHEN',
or where the power is made in the powerband.

Getting a valve lift into the region of where the head flows best is fairly easy.

The duration at which the valve is open at each lift point is determined by the
lifter's ability to ramp up the lobe and follow a 'wild' lobe profile.

A contour found on solid roller cam lobes that try to achieve the most duration
at higher valve lifts via a 'fatter' lobe nose is something that a flat tappet
hydraulic lifter could never follow.

As for the valve timing, that is dependent on a list of factors including RPM,
exhaust dimensions, intake runner dimensions, compression, etc.

Would it be fair to say, the camshaft should be matched to the engine as a
system, rather than just the head flow data?