Rocker Arm/Trunnion Wear

XLR8R

XLR8R

Crew Chief
Joined
Sep 10, 2007
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Saw pix of this before somewhere - searched to no avail.

These are from what I'm currently wrenching on:

RockerWear (Large).jpg
Rocker arms have some galling on the pressure side.

TrunnionWear.jpg
Trunnions exhibit similiar features, wear on pressure side is right at .001"

What's acceptable wear on these?
Won't polishing the rocker bores and trunnion ODs to remove the galling be fine, especially in addition to HPC-coating the trunnions?

All rockers & trunnions show more wear on their rearward side than the front - any ideas as to the cause of this phenomenom?
 
Mine look the same way, I have about 26k miles on them. Seems kind of strange to me.
 
I was in a 01 yesterday with the same problem. Some have mentioned the lack of ZDDP causes this condition. The truck in question has used Rotella consistently. I have recommended polishing and coating to see if the wear couldn't be reduced or avoided.
 
Rocker Lever Bore

Maximum - 22.027mm /0.867in.

Rocker Lever Shaft

Minimum - 21.965mm / 0.865in.
 
joefarmer said:
I was in a 01 yesterday with the same problem. Some have mentioned the lack of ZDDP causes this condition. The truck in question has used Rotella consistently. I have recommended polishing and coating to see if the wear couldn't be reduced or avoided.
Click to expand...

I have seen it in an 02 that ran Rotella. Which supposedly has more ZDDP than most oils.
 
Well, this truck had a pretty bad oiling history.

The wear limits barely mic'd out OK (thanks Ty), so I reckon there's enough room for the coating. :Cheer:

... now I just need to convince our lube engineer to recommend a sacrificial coating!
 
I had the same problem. I now machine them and use needle bearings.
 
hmmmm i am goona check mine really good next week when i pull the injectors and tighten the studs again...
 
X2 ^^^^

something like this...

kit786-1.jpg


since most of the wear is on the bottom, I wonder how well bearing would hold up.
 
Me too - the psi loading has to be an order or two of magnitude higher...
 
I don't have any pics but it looks something like that bearing. The bearing I have has alot more needles in it for support
 
You probably use a needle bearing without intervening dead space between the rollers - like in a U-joint cup... that'd be much stronger.

On this mill, we are going with a proprietary coating that has shown great results on piston skirts.

We also have a nifty machining solution that would address the (lack of) hydrodynamic wedge support across the bearing surface, but it does nothing for the dry-start issue... which IMO is responsible for the majority of wear.
 
XLR8R,

Since the shaft constantly rotates back and forth a small amount (and not continuously in one direction), developing a hydrodynamic wedge support across the bearing surface does not seem feasible... What did you do to address it?

In any attempt to correct the situation, I would think making the bearing the only item that wears would be a benefit (press fit into rocker and onto the shaft). That would make it possible to swap the bearings out every so often (50,000 miles or what ever is necessary) instead of needing to buy new shafts or rockers once they are worn out. If you used the bearing type shown above, it would still wear the shaft out and it would then require replacement...
 
you could put in a sacrificial wear item. Something that requires lots of attention. What about a brass bushing?
 
A few months back I contacted Harland Sharp about their rockers (the ones that Zach will be selling soon I think?) and it sounded as though they weren't recommended for the street or many miles due to the wearing involved. Not sure if they used a brass bushing or what?
 
GOT-Torque said:
XLR8R,

Since the shaft constantly rotates back and forth a small amount (and not continuously in one direction), developing a hydrodynamic wedge support across the bearing surface does not seem feasible... What did you do to address it?
Click to expand...

Exactly - I could have chosen the wording of my earlier post a bit clearer...

the oil film's thickness is inversely related to the highest-wearing portion of the rocker lever/shaft; machining to increase the oil film's width & thickness could only reduce or eliminate undesirable wear (especially galling).

As posted earlier, I chose to beta-test a proprietary coating for the problem areas in this engine's valvetrain.




Any kind of a brass/bronze (even if oil-impregnated) bushing in this application isn't going to have an adequate TBO on a high-mileage street vehicle.... just too soft.

Full-roller rockers, with needle bearing trunnions, offer low friction and long life.
 
Mine look the same way as well, and I have ran nothing but Amsoil since 10k. Weird.:aiwebs_029:
 
I got the coating on the trunnions done now. Seems like a winner. Maybe in a few months we can get some data for wear and report back.

The first photo is pre coating and 2nd is after the coating was applied.
 

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