rocker arm geometry
As Mike mentioned the 4.92 long valves that these heads are being built with, are too short for LA valve train. Couple this with aftermarket rocker arms that are probably too long and now things are messed up. LA heads need 5.0-5.02 long valves to get the geometry in the ballpark. And even then the scrub pattern may still be off. Most of the aftermarket rockers out there are poorly designed, leading to these kinds of problems.
As Mike mentioned the 4.92 long valves that these heads are being built with, are too short for LA valve train. Couple this with aftermarket rocker arms that are probably too long and now things are messed up. LA heads need 5.0-5.02 long valves to get the geometry in the ballpark. And even then the scrub pattern may still be off. Most of the aftermarket rockers out there are poorly designed, leading to these kinds of problems.