Valve clearance check question: How much cam lobe damage is too much?

[gsryan]

Hi All-

So, after watching Kerry's video, I embarked on the mission to check my valves.  I had been feeling that a valve was making just a little too much noise for my taste...  So, when I opened the valve cover, I wasn't too surprised to see some bad news (see photos below).  Not having replacement shims (and not really knowing what to do), I just turned the damaged one over and slid it back in place.  My questions are:  Was flipping over the shim a bad idea?  If so, why?  Also, is the lobe so damaged that I should replace the cam?  The Haynes manual shows an example of a damaged cam that looks way worse than mine.  The other three lobes and shims were perfect, so I don't really want to go through the trouble of replacing the cam if I don't have to.   

When I put it all back together and started the engine, it sounded better than before.  It could be my imagination, but I really do think it helped.  Any ideas/thoughts are appreciated.

Details:  1997, 7800 miles, stock intake/exhaust.

More info: when I checked clearance of the damaged lobe/shim, it was 0.04mm and when I flipped the shim, the clearance reduced.  I'll need to get a 0.03mm feeler gauge to make sure it isn't too tight.  Is it possible that the clearance has been too tight causing the damage, or something else??

Thanks in advance.




Ignore the lint...

[The Buddha]

Yeow ... anyway, keep an eye on it and since you swap shims just like make sure the scratched up shims dont get put in another valve.
I had a scratch on mine and mine was a clear crows foot type. In 50K miles it barely changed, My theory was that it took on oil and that prevented it from tearing up other stuff, however your case may be different. Mine was very distinctly crows foot type.
Maybe you can take it out and see if someone will smooth it in. Or hand sand with 1000 grit.
Cool.
Buddha.

[GeeP]

Ouch, that looks painful!   

Are the grooves in the cam lobe deep enough to catch your finger?

What I would be inclined to do is remove the cam and blend out the damaged areas.  Start with 220 sandpaper and work your way up to 1000 grit.  Blend in the damage with 220 in a wide, circular motion, then polish the surface by following the profile of the cam.  (So the sanding marks are parallel with the direction of rotation.  If you don't repair the cam lobe it will only get worse.

It looks like the face of the shim was savaged with a screwdriver before installation.  The surface of the shim must be perfectly smooth with no imperfections!  It also looks like the valve bucket and shim stopped rotating, which may be part of the cause too.  The shim bucket must rotate freely to distribute the wear evenly over the surface of the shim.