Rocker arm shaft bushings, Some have bushings some not? Options

[captjm]

Why do some used rocker arms for the Porsche 914 and 911 's have a bushing for the shaft? When was this added because I came across some without? I am assuming the later rockers have the bushings and it probably isn't a good Idea to mix.

[DRPHIL914]

Why do some used rocker arms for the Porsche 914 and 911 's have a bushing for the shaft? When was this added because I came across some without? I am assuming the later rockers have the bushings and it probably isn't a good Idea to mix.

others will have better explanation that me , but what i was told recently when replacing my heads and putting all new push rod tubes in and replacing my rocker assembly that sometimes you have to shim to get the right geometry for clearance with the rocker and the valve stem. I wanted to use swivel foot adjuster feet but didnt have room for them, turns out due to their length it requires addition of shims to give that room or you have to machine out the rocker to give room for the swivel foot adjusters , and some of this has to do with the length of your push rods too.

a engine builder will give better explanation, but that is my basic undersanding. I ordered shims but ended up not using the swivel or elephant foot 911 adjusters and went back to standard ones.

Phil