Cam Lobe 2/3 Gone OMG How did this Happen?
 

Pulled the valve cover last night on my 1969 280SE and discovered one of the cam lobes had a huge flat spot on it like someone held a grinder on it. Started it with the cover off and had a nice stream of oil, same as the other lobes, squirting on it.

History: B4 I bought this car it was throwing blue smoke. The seller convinced me to work on it with him. He said he had head work done recently and since then he believed a valve was not closing all the way. I worked on it with him and sure enough we found one of the thrust pieces (that sit on top of the valves) was cocked enuff to prevent the valve from closing completely. After freeing it, setting valve clearance and reassembling, there was a remarkable difference, engine purred like a kitten. Threw a little smoke on the way home but since has no visible exhaust. Yes, as it turns out it was the same valve that now has the destroyed cam lobe.

So my questions are these:

1. What happened to cause this? I am guessing that the valve was now closing all the way but perhaps warped enuff not to open all the way?

2. Do reconditioned heads, if I could find one, come fully equipped (i.e. with the cam shaft included?

3. Am I a nut to continue with this car, since all that metal has now gone down into the engine and done who knows what? Very least should I expect to pull the engine to inspect bearings on the bottom end?

Is really sad. The car is rusty (Wisconsin Salt Mine) but the interior is nice. I was going to pick up the 108 chassis from another forum member and transplant what I thought was the "good engine" into the rust free chassis.

I have a badly worn cam lobe on my 76 450sl that I've been researching options on.
-Metric Motors has a very good reputation on rebuilt heads. I've spoken to them and was impressed with the service I got (haven't had the job done yet). They basicially told me they can put a new cam in at modest cost over the regular head rebuilding cost. New aftermarket cams seem to run from $250 - $350; MB cams $600. That's for each, not per pair.

- I wouldn't worry about the metal in the engine thing. Lots of these old cars suffer cam wear - esp. the 450s. If you get a full head job in conjunction with the new cam(s) seems like you'd be in good shape.

- You can DYI the cam replacement. Some people say used cams are fine.

- But as to the ultimate question of why the wear happened, can't say. A lot of time it's clogged oil tubes, but you said that wasn't a problem.

It happened because the cam was running continuosly in contact with the rocker arm with a significant amount of pressure on it and probably cocking the rocker arm. Once the case hardening was worn off the lobe, the lobe dissapeared rather quickly.

Why would you want to replace the head, they dont come with cams. You probably only need a cam, rocker arms and the little lifter saddles that sit on top of the valves. Once you have the cam off inspeting the valve guides and changing the valve steam seals is very easy and will probably take care of your smoke.

If your worried about the metal shavings the only thing you need to be worried about is the oil pump. That is the only part that gets fed unfiltered oil. If you have oil pressure your good to go.

John Roncallo