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Project Addicted
Join Date: Jul 2012
Location: Eastern Shore. MD
Posts: 919
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Camshaft wear pictures
Hi all, we are getting ready to build a 3.4 from an '87 3.2 with 100K miles that needs a full on valve job due to bad guides with excessive oil consumption. We have purchased various parts from fellow PP members and I have some questions about some wear spots on the cams.
They are Webcam 20/21 grind, used with about 17K miles on them. There are some different wear spots on the backside of some lobes that I would like some input on. I can assume that the valves might have been adjusted too tight to leave these marks but I don't like guessing..... Your thoughts??     Thanks for taking a look. I appreciate your input.
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Jon 1966 912 1976 911 3.4 Backdate Project 1986 944 |
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01-07-2014, 09:36 AM
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Registered
Join Date: Oct 2008
Location: Nash County, NC.
Posts: 8,467
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When the rocker runs too tight, the polish runs all the way around the cam and produces some on the most radical burned and split valves.
Regardless, the defects are on the back side and have no effect on lift or longevity. Remember these are cast iron Bruce |
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01-07-2014, 10:09 AM
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Schleprock
Join Date: Sep 2000
Location: Frankfort IL USA
Posts: 16,639
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Those cam lobes look like they have remnants of the dry film lubricant on that WebCam applies to all of their camshafts? Doesn't look like actual damage to me.
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Kevin L '86 Carrera "Larry" |
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01-07-2014, 10:51 AM
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Join Date: Jan 2003
Location: Annapolis MD
Posts: 1,020
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Yeah ... Def looks like Dry Film that is wear away exposing the polished cam lobe under neath.
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01-07-2014, 11:20 AM
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Project Addicted
Join Date: Jul 2012
Location: Eastern Shore. MD
Posts: 919
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Why the wear marks then. If clearance is set right why the polished spot in pic 2? I accept that it's dry fil gone but is this evidence that the rocker was bouncing or something else. It's odd right?
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Jon 1966 912 1976 911 3.4 Backdate Project 1986 944 |
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01-07-2014, 03:22 PM
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Navin Johnson
Join Date: Mar 2002
Location: Wantagh, NY
Posts: 8,761
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Just observations..
Pic 1 and Pic 2.... nothing to do with wear from the rocker... Smudges in the DFL from assembly/dis-assembly handling packaging..... Pic 3 Note sure what you are concerned about in the circle you highlighted.. Pic 4 See Pic 3... Again where some of the packing material got jiggly with the cam
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Don't feed the trolls. Don't quote the trolls  http://www.southshoreperformanceny.com '69 911 GT-5 '75 914 GT-3 and others |
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01-07-2014, 05:22 PM
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Registered
Join Date: Jul 2006
Location: S. Florida
Posts: 7,249
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If you spray them with brake clean the remaining grey coating will wipe off. Then install with creamy assembly lube that stays in place. Or motor oil if the motor will be started again soon.
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01-07-2014, 07:27 PM
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Project Addicted
Join Date: Jul 2012
Location: Eastern Shore. MD
Posts: 919
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Thanks guys (and/or gals) for the input. Will lube well before installed.
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Jon 1966 912 1976 911 3.4 Backdate Project 1986 944 |
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01-08-2014, 08:09 AM
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Straight shooter
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Feeler gauge rubbing the film off when setting lift perhaps. Unless there's galling then nothing to worry about in my opinion.
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“Of the value traps, the most widespread and pernicious is value rigidity. This is an inability to revalue what one sees because of commitment to previous values. In motorcycle maintenance, you MUST rediscover what you do as you go. Rigid values makes this impossible.” ― Robert M. Pirsig, Zen and the Art of Motorcycle Maintenance: An Inquiry Into Values |
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01-08-2014, 08:13 AM
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P911
