Rocker arms questions
 

Cast vs Forged vs RSR

Can someone please explain when & where each were used. My assumption is that early rocker arms were forged and later switched to cast. If so can early be used in later arms?

Thanks

The early rockers were forged. The downside of forged ir their strength. The cast rockers are a safety devise that breaks if timing is jumped because of the tensioner failure.
Forged don’t break leaving everything to the crank to suffer.
Bruce

The early forged and later cast arms are interchangeable as assemblies, if I'm not mistaken.

The racing forged ones were used only in racing engines. They used different thickness lash caps for lash adjustment instead of the elephant foot screw adjustment.

early rockers were forged with screw adjusters for clearance. These have the advantage of light weight and strength. Strength can be a problem if things get out of wack as mentioned by Flat6pac. Some like to use these in high rpm race engines do to light weight. The rockers were changed to cast after a few years. Cast rockers are heavier but cheaper to make and were used until the 993 hydraulic rockers. RSR rockers are forged as well but instead of screw adjusters use lash caps for clearance adjustment. These were the lightest factory rockers. Currently there are some aftermarket forged light weight rockers available, most use the screw adjusters. These are made by Pauter, Schrick and 9M to name a few. These generally are engineered to be a more modern design to optimize weight vs strength for high RPM engines.

john