Help to ID these roller rockers and problem...

[rwhite692]

During teardown to do a piston swap for lower CR, I found that four rockers have a condition where the poly lock has galled / "chewed down into" the mating surface of the rocker's main shaft (trunnion)... I did not notice it at first, during teardown. The poly locks themselves look fine.

I didn't build this motor, so I don't know what manufacturer these rockers are. They have no markings on them anywhere, other than the "1.5" ratio on them. They sure look like Comp Cams pieces to me, but I can't be sure. Every set of Comp I've ever had, were engraved "Comp"

Pushrods all look fine, and there are no valvetrain geometry issues. I'm wondering if this motor was run for a time with the poly locks loose (or they became loose, and were eventually tightened) and that is what caused it? Or maybe over-tightening? I can't see over-tightening of the poly lock doing this, to what should be some pretty damn hard material (?)

Anyway, even if that was the case, I would think that the rocker shaft material should not have yielded to the poly lock like this, it's almost like the manufacturer didn't heat treat the shaft material or something. This motor does not have much time on it at all, like less than 2000 miles.

Here is what the rockers look like (these are ones that are OK):





And here is what the four "problem" rockers look like. The worn recess is a good 0.030" deep!

[GregWeld]

If Tom Nelson built that motor -- I'd be asking HIM WTF?

Almost looks at though the trunion was "upsidedown" when installed rather than the correct position (flat area on top to mate with the poly lock). But it's hard to tell what caused this issue.

[SDMAN]

See if you can find someone to do a rockwell test on the trunion. Any good metal shop should be able to do this. If these are cheap (chinese) knock offs, you found the problem. Lots of crap out there these days. Ive seen brand new cranks with indexing off +.010" and journal roundness out by over .002" right out of the box. Basically unuseable until its correctly re-machined. Lots of engine builders just bolt them in as is. Lots.

[rwhite692]

Originally Posted by GregWeld

....Almost looks at though the trunion was "upsidedown" when installed rather than the correct position (flat area on top to mate with the poly lock).

That was my first thought as well, GW, but, definitely not...The opposite side which sits on the rocker stud is spherical / no flat, on all of them.

[Vegas69]

Hard to tell without being there but they look to be machined. Could it be for a valve cover clearance issue or not enough thread engagement? Strange..

[rwhite692]

Hey Todd...No I don't think so...Only four of the rockers are affected. The studs are plenty tall and there is plenty of thread engagement....

I am going to replace all of them, It just bugs me to not know what caused it, because it seems like such a strange problem. I am leaning towards there being a material issue (abnormally low hardness) on the trunnion, the poly locks don't even show a mark on them. As was suggested I will check the rockwell reading on the affected trunnions vs. unaffected....I still would like to know who made these rockers, as well...

[Sieg]

What are the dimensions of the trunion from seat to seat on the good vs. appearantly bad?

[ProTouring442]

What do the pushrod guides and valve guides look like? If the rocker was allowed to turn even a slight bit, it could grind down the trunnion like that.

Shiny Side Up!
Bill

[rwhite692]

Originally Posted by Sieg

What are the dimensions of the trunion from seat to seat on the good vs. appearantly bad?

The worn recess is about .030 deep.

[rwhite692]

Originally Posted by ProTouring442

What do the pushrod guides and valve guides look like? If the rocker was allowed to turn even a slight bit, it could grind down the trunnion like that.

Shiny Side Up!
Bill

Bill, I don't see anything abnormal on the guide plates. I think you may be right about the rocker rotating on the stud. I am going to re-install one of the "good" rockers on each stud and mark the valve stem with dykem and rotate the assembly, to see if I can tell if the rocker's roller tip is moving laterally across the valve stem as it moves through each cycle.

I might also see if I can put a dial indicator on the side of the rocker and see what it's doing, but that will probably be difficult since the sides of the rocker body are not flat...so the indicator won't be able to follow correctly...

If the rocker is rotating on the stud that would be bad, since it would likely mean a lifter bore is out of square...I hope not!