Run in issues with newly grinded rockers and new camshaft

[Classic 911]

Hi.

I have issues with breaking in new rockers on new camshafts in my 911 SC engine.

The engine is a modified 3.0 engine with 3.2 RSR Mahle Motorsport cylinder and piston kit, RSR spec camshafts and 46MM PMO ITB`s.

The rockers are new original Porsche but grinded at a very reputable workshop that has been in the Porsche industry for many years. The reason for grinding the rockers was that they had bad grinding directly from the factory.

The camshafts was also new and also from a very reputable vendor to the Porsche community.

Oilpressure is great and cam tower spray bars are working as they shall.

Assembly of the rockers and rocker shafts was done dry then rockers lubed by hand in the oil feeding hole. Both camshaft lobes and rocker pads was pre-lubed with a very thin layer of DRIVEN brake-in grease.

Engine was cranked by hand until new oil came to the spray bars.

Engine then cranked by starter without fuelpump working, twice, until pressure gauge showed 1.2 bar before connecting fuel pump for first start up.

So to the case.

After the first 20 minuttes at 2000 rpm run in, using brake in oil from DRIVEN with 2400ppm ZDDP, there are "golden" residue on many of the rockers.

My thoughts are that this is wear from the rocker bushings being flushed out and flowed with the oil to the rockers and then "forged" between the surfaces during engine operation.

Can it be that the factory is using different bushings metallurgy on the latest rocker versions than on the older ones?

I also find the pattern on the rocker pads strange. It looks like they are not grinded good enough.

SO what do the fellow Pelicans think about these things?


With golden residue:



With golden residue and bad mating surface:




Rocker with bad mating suface:

[Neil Harvey]

I would suggest there was a problem with either the cam grind and or the rocker regrind work. Both need to be checked. The one piece of information missing from your post was the lash you were running. What was the cold lash suggested by the cam supplier? How does this translate into hot lash? Its the hot lash you need to know. Cold lash means nothing if the clearance goes away under running hot conditions.

How much material was removed from the rocker faces in their regrinding. Did it go through the hardness? What is the radius of curvature used? If this is wrong and off by a minute amount, the cam and rocker face contact are all wrong. This valve geometry is one of the worse for wear, when its wrong. Sliding steel on steel. Only the oil saves the day by removing the heat generated. Lash is there to allow an oil film to build up and remove this heat.

Also, what is evident is the appearance that you are running high spring seat pressure. There is a horizontal wear pattern on the rocker face where the rocker comes off the heel and onto the flank of the cam lobe. This always means the nose pressures are high and the contact stress numbers go through the roof.

[VFR750]

Also, did you replace or reuse the rocker shafts?

[Classic 911]

Originally Posted by Neil Harvey

I would suggest there was a problem with either the cam grind and or the rocker regrind work. Both need to be checked. The one piece of information missing from your post was the lash you were running. What was the cold lash suggested by the cam supplier? How does this translate into hot lash? Its the hot lash you need to know. Cold lash means nothing if the clearance goes away under running hot conditions.

How much material was removed from the rocker faces in their regrinding. Did it go through the hardness? What is the radius of curvature used? If this is wrong and off by a minute amount, the cam and rocker face contact are all wrong. This valve geometry is one of the worse for wear, when its wrong. Sliding steel on steel. Only the oil saves the day by removing the heat generated. Lash is there to allow an oil film to build up and remove this heat.

Also, what is evident is the appearance that you are running high spring seat pressure. There is a horizontal wear pattern on the rocker face where the rocker comes off the heel and onto the flank of the cam lobe. This always means the nose pressures are high and the contact stress numbers go through the roof.

Hi.

Cold lash was suggested by the cam supplier to be .1 mm and also set to .1 MM.

How much material was removed during regrinding I do not know, but as earlier stated the work was done by someone that is an expert doing this kind of work and I was told that it would be no problems with the rockers. I was also told this, and I quote:
"These pads are NOT hardened in any way since they are made of chilled cast iron..."

Spring seat pressure set at factory spec. using Porsche original springs, seats, shim and retainers.

Cheers
Eskild

[Classic 911]

Originally Posted by VFR750

Also, did you replace or reuse the rocker shafts?

Hi.

Only new rocker shafts was used.

Cheers

[gsxrken]

I’d send the cam and rockers back to the outfit that ground them and ask for some measurements and a diagnosis. Valve spring pressure would be good to know as well.

[Classic 911]

This is what the expert wrote back to me when I asked about my case:

Each & every one is ground parallel and checked in a fixture to ensure QC. The surfaces are ground 'just' enough to provide a clean surface with the correct Ra for oil retention without removing excess material. The factory surfaces are/were not parallel with the camshaft and rocker bores so thats corrected during the procedure.

These pads are NOT hardened in any way since they are made of chilled cast iron and don't need that process provided proper break-in procedures are followed along with proper lubricants.

Spring seat pressure was set to factory spec and springs, seats, shim and retainers were all new original Porsche.

[VFR750]

If the expert is correct, then it is something else.

What do the rocker shafts look like? Any sign of seizing?

Did you check the oiling holes in the rockers?

My reground rockers needed the holes to be chamfered to take the sharp edge off. The sharp edge can drag on the shaft and may limit the oiling. If the shafts and rockers stick, the pads can wear quickly. BTDT.

And a lot of cleaning to get the grinding swarf out of the grooves. It took me multiple passes of isopropyl alcohol, and sticky oil to pull the stuff out of the ground surface.

Same with the cam. If the surface has any residual grinding swarf (oxidized metal and cutting abrasive) It will be bad.

I had to use the same technique. Isopropyl alcohol wipe, wipe with oil, and repeat. Until the oil wipe no longer shows signs of darkening.

You may have done all this.

If everything was spotlessly clean, then it’s back to the expert.

[VFR750]

Seems odd that Brand new factory rockers were bad.

Is this a new problem Porsche should know about?

[OSC911]

I was under the impression that the replacement OEM Porsche rockers are now made in China and the best course of action was to get your old ones reconditioned. I am sure I have read a thread about these a while back.

[OSC911]

Originally Posted by VFR750

Is this a new problem Porsche should know about?

I don’t think they care. Just look at some of the junk they are manufacturing as replacement OEM parts.

[Mixed76]

Post a picture of the cam surfaces already

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[VFR750]

The only source of “golden” residue is from the bushing in the rocker.

[Classic 911]

Originally Posted by VFR750

The only source of “golden” residue is from the bushing in the rocker.

Exactly what I am thinking also..


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[Classic 911]

Originally Posted by VFR750

If the expert is correct, then it is something else.



What do the rocker shafts look like? Any sign of seizing?



Did you check the oiling holes in the rockers?



My reground rockers needed the holes to be chamfered to take the sharp edge off. The sharp edge can drag on the shaft and may limit the oiling. If the shafts and rockers stick, the pads can wear quickly. BTDT.



And a lot of cleaning to get the grinding swarf out of the grooves. It took me multiple passes of isopropyl alcohol, and sticky oil to pull the stuff out of the ground surface.



Same with the cam. If the surface has any residual grinding swarf (oxidized metal and cutting abrasive) It will be bad.



I had to use the same technique. Isopropyl alcohol wipe, wipe with oil, and repeat. Until the oil wipe no longer shows signs of darkening.



You may have done all this.



If everything was spotlessly clean, then it’s back to the expert.

Thanks.

All if this has also been done very thorough, almost to the extreme.


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[Classic 911]

Originally Posted by Mixed76

Post a picture of the cam surfaces already

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This is intake lobe on cyl. no. 1.
It is representative for the rest.




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[Mixed76]

Looks like foreign object, no change in scrape width across the cam lift.

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[Trackrash]

Are you running restrictors?

[Classic 911]

Originally Posted by Trackrash

Are you running restrictors?

No restrictors.


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[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