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New-ish 911SC Targa Owner
 
pampadori's Avatar
 
Join Date: Jun 2015
Location: Richmond VA
Posts: 277
Camshaft - Cyl 3 IN, what would cause this?

Background - rebuilt engine 1000 miles ago.
Noise heard, sounded similar to exhaust leak mixed with loose valve adjustment. Louder at 50% throttle. Louder after engine full temp.

Checked head stud torque, adj valves, looked for exhaust leaks - all in spec.

Noticed Cyl 3 int cam lobe looks "different".
Rocker arm and shaft seem ok to me but not that experienced.

What do the experts think about this brownish in color cam lobe? It feels rougher than the exh lobe next to it:
https://youtu.be/JKivcHusudc

Here is the removed rocker and shaft:
https://youtu.be/814hi1WQE6s

Is the cam toast? How about the rocker and shaft?
COuld this cause the noise I have been hearing?
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Shaun
'83 Targa 9.3:1, 2.7 crank, 930/52 case, AEM EPM, AEM Infinity 506, Triumph T595 throttle bodies.
'95 W124 E320 wagon (the daily driver)
'01.5 B5 S4 the previous money pit (sold)
Old 10-04-2017, 05:55 AM
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Join Date: May 2008
Location: Grapevine, TX
Posts: 158
At initial look I don't see any issues from the videos. Looks to me like you are comparing the lobe section of 1 vs the base circle of the other. I'd rotate the engine through and see what the other lobe section looks like for comparison. Looking at the rocker you can see the same color change on the pad th at contacts the cam. The area of shiny silver is the contact area, then you see the line where it turns dark which doesn't have contact.

Out of curiosity, what oil are you running?
Old 10-04-2017, 07:40 AM
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New-ish 911SC Targa Owner
 
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Join Date: Jun 2015
Location: Richmond VA
Posts: 277
Thanks for the reply. I'm using VR1 20w50 now that I've got some mileage on the rebuild.

I've put the rocker back in (which is a PITA without having the other shafts out for cyl 2 and 1).

Still not sure what the source of my noise is however.
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Shaun
'83 Targa 9.3:1, 2.7 crank, 930/52 case, AEM EPM, AEM Infinity 506, Triumph T595 throttle bodies.
'95 W124 E320 wagon (the daily driver)
'01.5 B5 S4 the previous money pit (sold)
Old 10-04-2017, 09:12 AM
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What work was done during the rebuild?
Old 10-04-2017, 09:53 AM
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Strange..
doesn't look like the cam lobe is making contact with the rocker does it.... the lobe next to it is nice and shiny but the one in question is all brown and "rough" looking...but that is probably the back side.
Can you rotate the motor a bit, and take another less shaky video, showing the offending lobe so we can see if it is making contact with the rocker?
Also, a pic of the valve and springs...
Old 10-04-2017, 11:53 AM
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Under the radar
 
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Join Date: May 2007
Location: Sebastopol, The Republic of California. Land of wine and redwoods.
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Your rocker looks good to me. You need to look at the top of the cam lobe.

I would CAREFULLY check to make sure all the cam squirter holes are clear. If there is a problem with debris in the cam oiling tube it will be around #3.
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Old 10-04-2017, 12:08 PM
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Had a valve seat drop on my brothers rebuilt 2.0 VW motor after a rebuild a decade or so ago. That made some odd random valve noise.
If they replaced the valve seats during head rework, you may want to look into that.
Old 10-04-2017, 12:38 PM
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New-ish 911SC Targa Owner
 
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Location: Richmond VA
Posts: 277
top of the cam lobe looks fine. Nice polished reflection like the exhaust lobe. I'll check the oil tube again to make sure its clear.
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Shaun
'83 Targa 9.3:1, 2.7 crank, 930/52 case, AEM EPM, AEM Infinity 506, Triumph T595 throttle bodies.
'95 W124 E320 wagon (the daily driver)
'01.5 B5 S4 the previous money pit (sold)
Old 10-04-2017, 12:52 PM
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Location: wisconsin
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Just to exclude issues, anytime you hear odd noises take off the alternator and air conditioner belts and run the motor...

Many a time I heard odd noises and turned out to be the alternator or air conditioner...

Also, did you try one of those mechanics stethoscopes?

Good luck,

Bo
Old 10-05-2017, 03:52 PM
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