re the end-float question
In another thread, Godge asks about rocker shaft end float which he is concerned about – and is also concerned that this will result in considerable noise.
Here are photos of the relevant parts.
I measured the float on eight rocker arms. It varied between 0.15 and 0.35mm. Like Godge, I found the left side to have the biggest gap. However it's fairly small movement and the parts are mostly rotating side-on with oil separation rather than primarily hammering against each other, so I doubt that the rocker shafts themselves are a source of big noise. That's only a guess though.
One end of the shaft rotates at the solid, fixed end of the support structure. That end does not butt against the support and there is a lot of end clearance. The lateral location and float of the rocker shaft is determined by the lobes at the other end, held in place by the bolt-on bridge. You can see the machined face on the bridge that the rocker shaft locating 'lobe' interfaces with. The float on this shaft arrangement in the photo is 0.25mm. These photos are of 'flat tappet' parts, however the rocker shaft is the same on rollers.[You must be registered and logged in to see this image.]
Plenty of end clearance here[You must be registered and logged in to see this image.]
This is where end float is determined[You must be registered and logged in to see this image.]