Original Equipment on the valve train for the Rover V8, uses high quality steel rocker arm shafts and aluminum rocker arms with hardened steel inserts where they work against the end of the valve stems. As you guys know, who have worked on these; replaced them, the aluminum rocker arms pivot point , surprisingly to some, don't wear as quickly as the steel shafts they rotate on, because the aluminum worn from the arms functions as an abrasive, wearing the shafts surprisingly fast. Now, I see, that one can buy replacement rocker arms that are made of a cast steel, rather than the aluminum ones. Anybody know, for sure, from practical experience, how the cast steel rockers compare to the aluminum ones, insofar as wear over time is concerned? What are the merits and the demerits of using cast steel compared to aluminum rocker arms? The fact that the cast steel ones are much heavier in weight, compared to the aluminum ones, how does that matter, if at all?

 

raising this old question as I am searching for the same opinions

 

I disagree with the wear premise posted by the original poster. The system is designed so that the valve spring and lifters always load the rockers in the upward direction, the rocker shaft oil holes are on the bottom of the shaft so that oil is pump between the two surfaces that would be touching. The rockers should ride on a film of oil, never touching the shafts. Of course when the engine is off, there is some contact, but there should still be an oil film there so that wear is minimal on startup. Of course, if oil pressure is below specification due to various issue, it is possible to have wear and contact. Also, I have seen Disco engines with so much sludge that the oil passage to the rockers are blocked. All that said, any time you design a system of moving parts in contact with one another, one is selected as the wear part and that part is constructed of the softer of the two materials. LR chose the rockers and used an AL alloy for the rockers and hardened steel for the shafts. Almost no engine has cast iron running directly on hardened steel, none that I have ever worked on and I have been working on engines for 40 years. Given proper lubrication, the cast steel should work ok but I would expect it to wear the rockers shafts faster than the the aluminum rockers. I think I would recommend going with whatever is cheapest and focus on good oil pressure and high viscosity oil to maintain the film. I have done 7 hg jobs, two on trucks with over 200k on them, several more over 150k, never had worn out rocker shafts, but then I do stay away from low oil pressure trucks for general wear reasons (rockers, cam, crank, rods, pistons, rings, etc).

Good luck.