I was pondering this recently- why choose stainless steel for a rocker arm material and not another steel alloy like 4140?

because stainless is pretty!

i can tell you that the crower ss rockers will take years of abuse.

Stainless wouldn't rust,

That's the only reason I could figure, but then again many other engine components are alloys that will rust and they aren't an issue.

Just personal preference, but I would rather run stainless than aluminum.

Me too, and that's what Bob put in my engine.

I'm just wondering why they didn't choose a stronger alloy. One could heat treat 4350 steel well north of 150ksi yield and wind up with a nearly indestructible rocker that would probably be cheaper than SS.

After some review, the Jesel steel shaft setups aren't stainless.

I've used the Comp Pro Magnums ( 8650 Chromoly ) without any failures. They claim 5% lighter at the valve than aluminum , long cyclic life.

The last set of crane gold aluminum rockers i replaced , went from 1985 to 2011. Out of 32 rockers, 2 had cracked trunnions. The trunnions were steel, not aluminum.

Steel bodies certainly have a higher cycle life. The bearings still wear though.

Icdedppl had comp cams steel rockers, the older ones . The geometry was awful with them. And they were no stranger to failure. Lots of guys had issues with breaking them, im not sure how the new XD series are.

All rockers are not the same. The comp steel, scorpion alum, and crane alum, all had a different measurement from center of trunnion to center of roller tip, even though they were the same ratio.

When i first put my engines together, i went with a pushrod that gave me a pattern that was most centered on the valve stem, because thats what i was told to look for. Simply a centered wipe pattern.

After 2 seasons i took things apart after reading up on the mid lift method. My setup had been throwing away a substanial amount of valve lift after measuring with a dial indicator on the retainer! Pushrods were too short. Sure it ran fine, but.....

Sorry for getting off topic, but i think theres more to rocker arms than material.

Well price has alot do do with it. Cast vs. billet, I prefer a thicker billet aluminum piece over a thinner cast metal piece. And once again I agree with Mild Thunder, there is more to it then material.