Rocker Arm Movement

[pryord]

While starting to adjust the valves on my '67, I noticed I'm able to move the rocker arms a tiny amount back and forth, as opposed to up and down on the valve.

Is a little bit of play normal? Should I be checking the torque on the 5mm allen bolt that secures the rocker arm on the shaft?

[hcoles]

there is a gap there that is normal is my understanding and was there on my 89 rebuild...tightening the bolt is not an adjustment method for this... likely the rocker will find where it likes to ride and just run there...or move a bit back and forth a bit which is probably good. I don't think the rocker bangs back and forth which would be the bad thing I can think of. Others on here know more.. that's my 0.02.

[304065]

They do move, they will slide opposite the high spot where cam and rocker face meet. If you look at a used 911 camshaft the lobes usually show wear on one side, this is because the rocker mates unevenly with the cam.

One thing you should check 'while you are in there' is the length of the rocker shafts. The very early ones are 18x48mm, the later ones are 18x53mm. You probably have the later ones as I think the changeover point was for the 1967 model year. My '66 had a mix of both. The factory changed over presumably to spread the side load over a larger area and improve sealing of the shaft.

And yes you should check the torque. As you probably know, in 1967 the factory changed the rocker shaft pinch bolt to 7mm from 6mm diameter. The early narrow diameter bolts would stretch into the plastic range and not hold the ends of the shaft expanded against the rocker bores and they would walk. M5 is the size of the internal wrenching feature, screws are usually referred to by the diameter of the shank (thanks Jim Sims!)

I wouldn't be concerned unless there's a lot of movement which would suggest that the aluminum cam carrier bore is distorted. This isn't very easy to check on the car, though. With the shaft and rocker removed you can kind of get your finger in there to see if the bore is roughed up, scratched, distorted etc.

More here on pinch bolts. Keep the SWB faith!

Rocker shaft pinch bolts

[pryord]

Wow, great information. Thanks!

[Peter Zimmermann]

I would approach the rocker shaft bolt issue from a different direction. I've found, once they're tight, that the best thing is to leave them alone. Before attempting to re-torque a rocker shaft I get out the old dentist's mirrors, a small flashlight, and check for oil seepage at both ends of each rocker shaft. If there is some, and it will be obvious, then it will be worth it to check the shaft tightness. If the ends of the rocker shafts are dry there is no need to do anything to them. Oh, and yes, the rocker arms will always move sideways on their shaft...