TR4/4A I Pulled the Rocker Arm Off

Because I can't live with the rhythmic rat-a-tat of the valves. I adjusted to .010 but I still get the noise from the back two valve rockers, or at least I think that's where it comes from.

Now that I've got the rocker arm shaft completely off, what do I look for on the individual rocker arms? They all have a face that looks highly polished and rounded, sort of convex. Is that normal?

Also, two of the rocker pedestal studs were loose. Is that normal? I seem to recall being told to put them in "finger tight" and let the torque and nut tightening do the rest. Was that correct, or is there a problem with loose studs. Seriously, I could remove two by hand after removing the rocker arm.

Finally, on two of the rockers I see a small flat spot on the ball fitting "adjuster" that hits and "fits" the tappet rod end. Maybe no big deal there?

Rocker face should be as you describe and studs should be tight, although I don't know the spec. Have you double and triple checked the clearances? Tom

According to the service instruction manual, "rocker pedestal 24-26" -that is foot lbs of torque. I would torque it down, and set the clearance. While running, you can carefully lay a screw driver on the shaft next to each rocker and against your ear, and figure out which are making the noise. A length of hose may work as well. Then you can tighten those up a little more until they quiet down, but it may affect performance. Most of us just live with that sewing machine noise.

TexasKnucklehead said:

According to the service instruction manual, "rocker pedestal 24-26" -that is foot lbs of torque.

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I think KVH was asking about the force applied to the studs. The 24 - 26 refers to the nuts on the studs, which can be achieved with the studs loose in the threads, but not he best practce. Tom

The most likely source is the contact area between the rocker tip radius surface and the valve stem. I spent a lot of money eons ago to get the radius tips remachined and they were wonderfully quiet for about six months before developing enough of a flat spot to get as noisy as before. The factory had some variety of surface hardening done to these things, so the only thing I can suggest is trying two new replacements if you are certain they are the culprits. Why just those two is sort of problematic. All of mine were equally flat spotted as I remember.

I checked mine again. Each has a small little dimple toward one side or another--none in the middle of the rocker. However, it makes me wonder what created that dimple. I'd estimate each is no larger than about .003 deep. Each is to the side, none in the middle. So, naturally, I can't tell that's really where the stem hits anyway. What if I use a polishing stone or fine wet and dry sandpaper and smooth out the dimple, leaving the rest of each rocker alone. Will I make a bigger mess?

In my shade tree opinion, there is normally a visible contact area on the rockers but you should not see a spot that is worn flat or creates a sharp edge. Best to get them dressed by a valve grind shop although I don't believe this is causing the noise. I don't think you will make a lot of progress with wet and dry but I don't think you'd gain much either. The surface is quite hard. If you really get aggressive, you may alter the radius.
Tom

Sounds to me like the rockers or valves are mis-machined, causing the rocker tip to not lay squarely on the valve end. Might be just wear in the shaft/bushings, though.

The tips are supposed to be machined to a specific radius, to maintain the contact patch near the center of the valve stem as the valve opens. If you start trying to modify them yourself, try to maintain that radius.

Or just send the whole thing off to Rocker Arm Specialists to be rebuilt.

BTW, running with the valves too tight, especially exhaust valves, risks burning the valves. Probably not a good idea.