Run in issues with newly grinded rockers and new camshaft

[Classic 911]

Originally Posted by ahh911

I just looked at my re-ground rockers by Craig G, they are so shiny from tip to tip. What's all the grey stuff on the ends of the rockers? That looks like a very rough finish compared to mine, were they like that when you installed them?

Phil

Yes they were.


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[VFR750]

Found a picture of my rockers from November 2015.



Condition after 1,119 miles.

DC20/19 cam, DRC Race Springs, 20-50 oil.

Note the smoothness of the ground surface on both #2 Intake and #2 Exhaust.

Note the damaged #2 Exhuast rocker and the rocker shaft surface. Most Intake rockers looked this way.

High spring load, and binding rocker/rocker shaft destroyed the rocker in 1,119 miles.

More Pictures:







Repaired Rockers
Replaced Rocker Shaft
Reground DC20/19 (again)
Stock Valve springs.

Solved the issue.

[VFR750]

Ran the Winter 2015-16 rebuild for two years and several trackdays.

6,134 miles later: Best picture i got. Cams and rockers look great



Upper is DC20/19 cam with 6,134 miles. Lower is new DC40. DC 40 cam now has ~8500 miles with no issues. (Stock springs)

[VFR750]

Are you sure your rockers and cams started out smooth enough?

Too rough of a surface will overcome film thickness strength. Cut right through it.

[ahh911]

hmmm, someone who has looked at more than one 911 could comment, but if they came like that it looks like the rocker arm grinder was out on vacation. Sorry, hopefully someone else confirms that it looks far too rough on the outer portions and should have been mirror finish.
Phil

[Classic 911]

Originally Posted by ahh911

hmmm, someone who has looked at more than one 911 could comment, but if they came like that it looks like the rocker arm grinder was out on vacation. Sorry, hopefully someone else confirms that it looks far too rough on the outer portions and should have been mirror finish.
Phil

Yes they did


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[VFR750]

My rockers were very smooth. And still are.

My Picture of undamaged (#2 intake) rocker on the right is after 1,119 miles

And the DC20/19 cam lobe after 6,134 miles looks and felt smooth as the glass it looks like.

[Classic 911]

Can somebody tell what Ra cam lobes and rocker pad shall have when new/new grinded. And what grit is used during the grinding process.


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[Classic 911]

Hete are some pics of two rockers I have polished.
First one with only 1200 grit. Next one with 2000 grit.


In this one I can see my face quite clear, undortunately



This one can see my hood crest in a quite shiny pad.


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[VFR750]

Seems they could polish up nice, but are they really flat as needed?

How did you lube the rocker, shaft, and cam prior to starting? What lube did you use?

[reclino]

I am planning on sending my cams and rockers to be REM super finished. I don't believe just polishing them on a buffing wheel is going to get the correct surface profile.

[gsxrken]

Would be great if @camgrinder or other boutique camshaft machinist would weigh in.

Cams and lifters in other applications are not mirror polished. Some cam lobes almost look parkerized.
Cylinder walls are purposefully left with som RA# for oil retention.
Cranks can be micropolished but bearings are not.

Given all the evidence the OP has presented, I have to wonder about the regrinder who felt that “The factory surfaces are/were not parallel with the camshaft and rocker bores so thats corrected during the procedure.” If they were corrected, why is there an issue now? Were they correct and modified to be incorrect? Does Porsche really not grind rockers correctly? Or was it a bad bushing job (thus the golden particles) that cocked the rocker face relative to the cam... but instead of rebushing, they reground the face?
The Sherlock Holmes after eliminating the impossible quote comes to mind.

[Emo993]

Just a shot of my cams and rockers from John Douhterty, DC30. Not polished but very nice finish. Mark

[ahh911]

Does it seem possible that only a partial profile section gets a different treatment? Has anyone seen this on a 911 rocker arm?

Classic911, could you feel the surface difference along those rough looking patches highlighted?

Phil

[Classic 911]

Originally Posted by ahh911

Does it seem possible that only a partial profile section gets a different treatment? Has anyone seen this on a 911 rocker arm?

Classic911, could you feel the surface difference along those rough looking patches highlighted?

Phil

Hi Phil.

Yes I could feel the "golden" rough patches quite well with my finger nail. It is a layer on top of the rocker pad face.


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