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Join Date: Dec 2006
Location: South Africa
Posts: 76
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Rocker Arm Shafts... what if??
Hi, easy Q&A for the experts, please ...
Why should rocker arms be installed flush with the thinner flange of the housing? Leading to... what would happen if they are flush with the thicker flange of the housing? .... When to expect something, if anything? Many thanks.
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_________________ Jacob 911 2.7s - 911 SC - 911 3.2 Carrera |
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07-14-2009, 09:13 AM
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I would rather be driving
Join Date: Apr 2000
Location: Austin, TX
Posts: 9,108
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The rocker shaft has a slot cut into it on each end that matches the width of the rocker arm. To the outide of this slot is the expandable end that effectively locks the rocker shaft to the cam tower upon torquing the bolt. If the shaft is aligned to the thicker end then the rocker will ride/pivot on the expandable end. This will wear out the rocker bushing. it will also limit the surface area of the rocker shaft engagement on the thin flange of the cam tower. This could wallow and damage the cam tower.
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Jamie - I can explain it to you. But I can not understand it for you. 71 911T SWT - Sun and Fun Mobile 72 911T project car. "Minne" - A tangy version of tangerine #projectminne classicautowerks.com - EFI conversion parts and suspension setups. IG Classicautowerks |
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07-14-2009, 09:41 AM
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Join Date: Jul 2006
Location: S. Florida
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Jamie's answer is correct.
Hold a rocker shaft up next where it goes in the cam tower and look at how the part of the rocker shaft the rocker arm should be on and how the expansion slots at the neds of the shafts line up with the thinner and thicker rocker shaft bores. Then it should be obvious how it goes. |
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07-14-2009, 10:18 AM
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Makes sense, Jamie.
Would you recommend waiting for the first valve adjustment job to have this fixed (Just did a top-end-rebuild > then discovered mistake) or rather do it now? (hard to face since the car finally starts)
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_________________ Jacob 911 2.7s - 911 SC - 911 3.2 Carrera |
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07-14-2009, 10:19 AM
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If your rocker shafts are installed wrong reposition them ASAP. I would not even start the car because you are ruining the bronze bushing in the rocker shaft if the expanded section of the rocker shaft is partially inside the bushing.
The rocker arms should have been noticably stiff and raised concern as to why when adjusting the valves if they were like that. If you've run the car with them like that the rocker shaft bushings are already compromised or ruined and should be rebushed. They may seem to work OK, but the rocker arm bushings are going to be heavily worn where the expanded end of the shaft was inside part of one end of the rocker shaft bushing. The rocker shaft may have noticeable wear in that area if you measure it's diameter with a micrometer. |
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07-14-2009, 10:37 AM
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Got the picture, thanks all.
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_________________ Jacob 911 2.7s - 911 SC - 911 3.2 Carrera |
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07-14-2009, 10:51 AM
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