What causes the valves to rotate?   After pulling my heads and lapping the valves,  I noticed the ends of a couple valves clearly show the rubbing of the rocker arm straight across the end of the stem.   These valves were brand new when I put the heads on my engine 400miles ago.  On those valves I can see a straight up/down pattern on the shaft.   There were all new guides installed in these heads. none seem too tight to prevent rotating.   So are these valves bad,  or are the rockers?

The design of the mushroom lifters causes them to rotate thus turning the pushrod. This is the way it's supposed to be for the best oiling.

Y's guys rule!
Looking for McCullouch VS57 brackets and parts. Also looking for 28 Chrysler series 72 parts. And early Hemi parts.

MoonShadow, 292 w/McCulloch, 28 Chrysler Roadster, 354 Hemi)
Manchester, New Hampshire

I did not know our valves rotated. MoonShadow described the lifters and pushrods which have no contact with the valves. There are engines with valve rotators on the top of the springs.

56 Vic, B'Ville 200 MPH Club Member, So Cal.

A lifter turning and pushrod turning have nothing to do with valve stem rotation.  They do not come into contact with the valve stem and cannot affect the rotation unless the rocker arm is not centered and pushing the stem at an angle.  Spring harmonics  with too soft springs will cause the valves to bounce off the seat, or loft over the camshaft lobe.  Your valve with the nice even pattern on the top is working exactly as it should.  If the tops of the valve stems show a pattern of continual rotation, the spring rate was wrong for the camshaft lift and/or not enough seat pressure at installed height.  Joe-JDC

JDC

Yes, the valves do rotate under normal operation albeit slowly. Some valves have rotate mechanisms to ensure they rotate at a predictable rate.

The rotation action helps keep the valve and seat clear of debris to ensure good sealing. I think Ted will confirm this when He reads this Post.

  

Once again I get caught reading too fast and missing the issue. Sorry guys.

Y's guys rule!
Looking for McCullouch VS57 brackets and parts. Also looking for 28 Chrysler series 72 parts. And early Hemi parts.

MoonShadow, 292 w/McCulloch, 28 Chrysler Roadster, 354 Hemi)
Manchester, New Hampshire

Valve rotation is as a result of valve-train dynamics. There is nothing to prevent the valve from rotating.

Rotation will increase with engine speed. Thai is why a HD Engine will have valve rotators as they are operated at lower RPM and subject to much more cylinder heat.

Let's see if I pass the quiz once TED showers and shaves ...

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I appreciate the feedback.   Any truck info I've read has mentioned rotators on industrial and truck engines.   Someone spent good money on these heads before I got them.  New valves,  new guides with spring loaded valve seals,  double springs,  and hardened valve seats.   They didn't lap the valves,  just put them in.  They must've assumed they would seat themselves.    After a compression and leak down test,  I had one cylinder down.   The hardened exhaust seat had a punch mark in it leading to the leak.   Lapping took the mark out,  so I lapped them all.   I just didn't want to have to pull the heads again for an issue with the valves rotating

i dont lap my valves but i do check them.i turn the heads over and install the plugs and fill the combustion chambers with water and leave them overnight.any leaks will show.

The springs themselves have a natural tendency to rotate due to their spiral nature.  The idea behind the original two piece valve spring retainers is to promote valve rotation.  Going with single piece retainers does slows that rotation down but does not stop it.  In the grand scheme of things, you want the valves to rotate to promote even wear at the seats as well as helping to keep the seats and valves clean.  Badly worn rockers can create enough drag at the valve stem tips to inhibit valve rotation.  Here are some videos showing the valve springs rotating on performance engines.
 
https://www.youtube.com/watch?v=WtqDHJDN79w
https://www.youtube.com/watch?v=019Jyn9oB5k
https://www.youtube.com/watch?v=ijYC8LbB5ZI

Lorena, Texas (South of Waco)