This explanation doesn't make sense. We are not talking about a single camshaft that functions both intake and exhaust cams like the overhead valve cam in block engines.
Since the intake and exhaust lobes are on seperate shafts, increasing overlap would be done by degreeing one or the other of the two shafts. That is the overlap or split could be changed merly by how each individual camshaft is installed.
It is common on the OHV engines (Chevy 350 for example) to increase overlap by changing the angle between the intake and exhaust lobes. Known as the "split". The character of the cam can be greatly altered by changing the split while the lobes stay the same. Mild RV cams are often 114 degrees split while hotter cams are often mote like 108 or 110 degrees.
Variable valve timing in modern engines alters this split while running depending on commands from the PCM. It is common to alter only the intake cams on performance oriented engines or sometimes to alter only the exhaust cams on emissions oriented engines.
Without getting into a huge discussion on valve timing something about changing the overlap on the Duratec from the above explanation doesn't ring true. Am I missing something?
