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

[stownsen914]

I know early 911 rockers didn't have bushings. They can be machined to add them as part of a rebuilding process, in case you run across an older set.

[914werke]

Bushings or shims?
All 914 (/4) rocker (shaft) assemblies used springs & washers not spacers.
Some T2 buses with hydraulic cam & lifters used spacers (& steel P/R's) instead.
It is common practice when updating or servicing your heads & valve-train to replace the OE hardware with Alum. spacers & a combination of machining of blocks & shaft spacers to adjust rocker geometry to its optimum contact.

[DRPHIL914]

Bushings or shims?
All 914 (/4) rocker (shaft) assemblies used springs & washers not spacers.
Some T2 buses with hydraulic cam & lifters used spacers (& steel P/R's) instead.
It is common practice when updating or servicing your heads & valve-train to replace the OE hardware with Alum. spacers & a combination of machining of blocks & shaft spacers to adjust rocker geometry to its optimum contact.

ignore my previous post, as i re-read this i agree with 914werke, OP was referring to the spacers on the shaft here and answer is (IMG:style_emoticons/default/agree.gif) what he said, can be used rather than the springs. I put these aluminum spacers on the shaft for my current build.
just make sure that the spacers are adjusted to make sure for proper alignment of the rocker to be directly over and square to the valve stem.

Phil

[mgphoto]

The parts should have a number on them, look up and see if the bushed rockers are a redesign or a modification for rebuild. Seems logical that the rockers could be bored out and fitted with bronze bushings during a rebuild, like valve guides.

[Jack Standz]

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.

Like other improvements/changes during Porsche and VW production runs, it was an ongoing process. This change was probably done to improve function and/or reduce costs. For example, early gauge surrounds were painted steel, later ones were plastic. Functionally equivalent (?), but plastic ones probably cheaper to produce.

Don't really see a downside to mixing the rocker arms as long as the interface between the rocker and shaft are within tolerances. Maybe check that the ratio is the same (some builders go through lots of rocker arms to get ones that all match, others don't care).

[Jack Standz]

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

Conventional opinions are that shims under the rocker stands is not the best way to set up rocker arm geometry. Due to height limitations, most/all Type IV rocker arms will need clearancing under the rocker adjuster tips to prevent binding when running 911 swivel adjusters in a Type IV motor.

You will also almost certainly need to cut custom length pushrods and spacers will likely be the best way to setup the rocker arms for proper alignment of the rocker arm and sweep across the valve tip. Just part of the build process, especially if you're straying from pure stock.

Here's Ian Karr's video that is a good place to start:

https://pmbperformance.com/pages/ian-karrs-...ne-build-videos