But I am interested in the Lift----IN/EX numbers. Are you referring to the lift of the cam? I don't understand. I know the springs need to handle the lift and the heads need to be cut to handle the different types of springs that need to handle the different lifts. Is that what this list is referring to?
The intake and exhaust numbers listed is what THAT head porter gets on a fully ported head porting. That’s what the head will take in (air and fuel at wide open throttle. Not at part throttle when your cruising the Hwy.
You are correct about the bigger cam lift needing springs and the heads cut for the springs is partially correct because that is dependent on the spring itself.
The cam lifts the valve to .538 with a 1.5 rocker.
With a 1.6 rocker, lift goes to .573.
That would require in many cases a new spring over the listed one at the lower lift.