Strange cam specs

“Generally”, the rotator and spring on the exhaust will not accommodate much more lift than the factory cam.

If I’m going thru factory SBM heads, and there is any hint of a performance slant on the build, and the heads have rotators on them………the factory 2 groove valves and rotators get replaced with their non-HD equivalents(at a minimum).

It’s probably not a bad idea to pull an exhaust spring off, measure the installed height, and check the spring in a vice for available spring travel from the installed height to c/b.

I’ve seen it where people have put springs designed for the taller IH of the std retainers, on the exhaust valves with rotators……..which results in very little available spring travel.