Hi, This sort of relates to what I have been talking about in another area.
A lot of engine builders in Aust are not keen on full PAO synthetics. They claim that roller rockers usually suffer from a lack of lubrication in high performance applications.
A well known racing and engine building company also claim that Valve Train parts also suffer from lack of long life
out of various valvetrain components with Synthetics.
A major Head and Valve Train component company here void all warranty if your found using a Syn oil with there products.
A major Cam company here also strongly advises against the use of Syn oils with there Cams.
Even Crower Cranks make a comment in there FAQ section on there web site, that the possible ware and damage effects of Syn oils in V8 engines far out way the slight HP gains and only recommend the use of quality mineral.
I believe that with the large valve sizes (2 valve cylinder), low (relative) revs (7500) but "high" lifts via the pushrod and associated translation devises, the cam followers, rockers the stressed interfaces on these items appear to benefit from the characteristics of the mineral oils.
While Technically Speaking they don't compare to Synthetics, this being in a tube in a lab, and more so on the advertising brochure. However on the Tar in an engine I go on word of mouth combine with revenant Technical data. I make it very clear I am no expert, only a student of Oil, and I feel that yes in curtain applications they are great things. But don't write off the Old reliable Mineral Oils just because the broachers aren't as shinny. Sure you do have to change it more often, but I like the thought of always having clean oil in a clean engine.