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Registered User
Join Date: Oct 2005
Location: Mahwah, NJ
Posts: 312
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Rocker Arm Shaft Question
How much wear is considered acceptable for the rocker arm shafts? I was disassembling my heads last night and was surprised at the amount of scoring that I noticed on my shafts. Is this considered "normal" wear? Thanks in advance.
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Mark 1987 Carrera 1990 Mazda MX-5 2002 Chevrolet Duramax Crew Cab 2008 Harley Davidson FLHX Street Glide |
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02-15-2007, 05:40 PM
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I Calls em as I sees Em
Join Date: Jul 2003
Location: Cross Roads
Posts: 6,078
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I am thinking anymore then a shadow would be too much
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"Kracklin Rosie"....1975 S, red duck, 2210 lbs total ( full tank). No front license plate. I have issues. I calls em as I sees em................. |
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02-15-2007, 08:52 PM
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Registered User
Join Date: Apr 2006
Location: Newcastle, WA
Posts: 968
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You can measure the outer diameter with a caliper. I recall mine were 18.02 mm, surprisingly all of them were. There are tolerances mentioned in Wayne's book.
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James 1969 911E Slate Grey 1981 911SC Wine Red 1997 911C4S Ocean Blue |
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02-15-2007, 11:13 PM
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I Calls em as I sees Em
Join Date: Jul 2003
Location: Cross Roads
Posts: 6,078
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I would be concerned for reason for the "wear"
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"Kracklin Rosie"....1975 S, red duck, 2210 lbs total ( full tank). No front license plate. I have issues. I calls em as I sees em................. |
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02-16-2007, 04:42 AM
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Registered User
Join Date: Feb 2004
Location: California
Posts: 875
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I consider more than .0003" unacceptable.
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John Dougherty Dougherty Racing Cams |
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02-16-2007, 02:05 PM
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Registered User
Join Date: Apr 2006
Location: Newcastle, WA
Posts: 968
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Wow, 3 10thousandths! My micrometer isn't that good, but no wonder they were all 18.02. Thanks camgrinder.
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James 1969 911E Slate Grey 1981 911SC Wine Red 1997 911C4S Ocean Blue |
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02-16-2007, 02:12 PM
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Moderator
Join Date: Dec 2001
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Well, I don't have a spec book for an '87. You should absolutely have one, or the factory workshop manual, to guide you through all mechanical work.
My old book for the '65-68 cars says the specs are: Rocker arm shaft: 17.992-18.000 mm So the difference is 0.008mm, or 0.00031496063" (which is exactly what Camgrinder said, 'cept in "English."  )The rocker shaft bore in the cam housing is listed as 18.000-18.018.
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'66 911 #304065 '71 911E PCA H-Stock Club Racer #806 Ex-'88 Carrera (Sold 3/29/02) Ex-'91 Carrera 2 Cabriolet (Sold 8/20/04) |
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02-17-2007, 11:58 AM
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Registered User
Join Date: May 2003
Posts: 2,922
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Some scoring seems to be common on the shafts. That doesn't mean they are worn out. You can check with a micrometer. I install them with the scored surface on the "outside" so the smooth surface wears for the second life of the engine. Worn out rocker arm shafts and bushings will be noisy. Not dangerous but annoying.
-Andy
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72 Carrera RS replica, Spec 911 racer |
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02-17-2007, 04:27 PM
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Registered User
Join Date: Oct 2005
Location: Mahwah, NJ
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Thanks for the input. I'll "mic" them tomorrow and see where I am at.
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Mark 1987 Carrera 1990 Mazda MX-5 2002 Chevrolet Duramax Crew Cab 2008 Harley Davidson FLHX Street Glide |
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02-17-2007, 06:14 PM
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Registered User
Join Date: Nov 2000
Location: Dallas
Posts: 2,649
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Anything wrong with Eagledriver's process? Aren't these under pressure from the "bottom" only?
Thanks
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Buck '88 Coupe, '87 Cab sold '88 535i sold (really miss it) '07 A4 DD Warren Hall, gone but not forgotten |
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04-07-2008, 12:33 PM
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