W113 Pagoda SL Group > Drive train, fuel, suspension, steering & brakes

Rocker arm wear

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wwheeler:
I think I know the answer to this, but would like an experienced hand but confirm. I am attaching a picture of my rocker arm and the matching cam lobe.

I was doing a valve adjustment today when I noticed this abnormal wear on a rocker. I had to take the arm off because the ball pin was too tight for a crow foot wrench and used a socket to turn the ball pin. On the rocker, the wear surface has been "chipped off" on the forward edge of this and most of the rockers. There is a definite cliff when you run your finger nail over it. That wear surface is a grayish color and looks to be a surface coating. The mating surface on the cam is not "chipped' but actually feels slightly raised. It feels like the rocker surface chipped or wore of onto the peak of the cam lobe.

I replaced the rockers about a 1-1/2 ago (1500 miles) when replacing the ball pins. The cam is original. I bought the rockers from an well-known aftermarket company. Is it possible that they are defective? I didn't use a cam break lube at the time thinking it wouldn't be necessary. Is that correct? What to do now? I think I should replace the rockers (from MB this time!)immediately and maybe LIGHTY file the cam lobe to remove the built up area on the cam lobe. I don't think the cam's hardened surface was disturbed but rather the rocker's softer wear surface was deposited on the cam.

Help please!

ja17:
Hello Wallace,

Yes the hardened surface of the rocker is failing.  The cam should be ok.  Since your cam is used, some good condition original rocker arms should be fine. New rockers running on an old cam is a bit over kill.

wwheeler:
Thanks Joe. Is it OK to put new high quality arms (from MB) on with an old cam? I would rather make sure I get good ones on and not ruin my cam with a possible bad used one. This is an area I don't mind spending more if it prevents a failure.

Given that the current arms were only 1-1/2 years old, do think they were poor quality or could something else have caused this? Why is this premature wear only on the front leading edge? Do the cam/arms tend to contact there first?

I use Valvoline VR1 20w-50 oil and the cam area receives lots of oil. I don't think that could be the problem. I adjust the valves regularly to .003" (intake) and .007 (exhaust). Anything else I should look for?

Thanks for the reassurance!

Benz Dr.:
Our engines use what is commonly known as '' flat tappet '' followers or rockers. Ever since they removed the zinc from most engine oils I've been using either a synthetic 10W40 or a 14W40 oil used in diesels as other oils often don't have the anti wear protection required. I also use Lucas products where needed.

The rockers you have seem to have worn rather quickly. Original ones have a chrome plated surface area where the cam rides but I can't say what the repros have. I've seen both the cam lobe and the rocker wear but I believe that it was a case of extended use after the initial wear had occurred. In any case, the loud tapping noise at idle would have been a clear indication that something was wrong but was ignored for years resulting in severe cam shaft damage.
   

wwheeler:
The VR1 oil I use says that it has high levels of ZDDP and is a racing oil specifically for mechanical tappets. I think it should be OK. I removed ALL of the rockers today and found that all of them had wear. 60% had the hardened area chipped on one edge, 35% had been chipped on both edges and one was chipped on both edges AND was chipped in the middle.

Chipped is really a better description because "wear" would suggest a smooth transition. There is literally and .003 drop off where the material has been removed. It is like the bond between the base metal and the coating has failed. Then the coating just popped off. Because it is mostly on the edges, I am assuming that it is a manufacturing defect. Edges are typically the most vulnerable bond areas.

Would the replacement MB rockers have chrome plate like the originals? This coating is definitely NOT chrome but looks something similar to the Titanium coatings except it is a dull silver. I wish had never got rid of my original rockers to begin with!

What do you think?   

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