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Registered
Join Date: May 2006
Posts: 36
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911 SC Cam orientation
I just completed some valve work on my #6 cylinder, and I did not disturb the left cylinder bank side. If you have Z1 lined up with case parting, and rotor pointing at #1, and you have the 930 mark on the right cam at the top, is that proof positive that the left cam also has the 930 at the top?
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06-28-2008, 04:27 PM
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Registered
Join Date: May 2003
Posts: 3,346
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I don't remember if having the cam marks up means that number 1 is on the top of the compression stroke or on the top of the exhaust stroke. You know for sure that when the rotor is pointed at number 1, that cylinder is on the top of the compression stroke. If you install the cam for the right bank such that it's on the top of the exhaust stroke you will have the cams correct. (this assumes you never removed the distributor). Look at the lobes and the direction of rotation to see what stroke the cam will be on with the 930 up. The exhaust should be just closing and the intake should be just opening for number 4 cylinder.
Hope this helps. -Andy
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72 Carrera RS replica, Spec 911 racer |
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06-28-2008, 07:37 PM
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GAFB
Join Date: Dec 1999
Location: Raleigh, NC, USA
Posts: 7,842
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I'm not much of a visual thinker. Like Andy, I can't remember if TDC ignition on 1 means the cam dot is down or up. Actually if I had a gun to my head, I'd say TDC ignition on 1 means that the dot is UP.
Just pop your upper left valve cover and check the cam. If #1 is on-cam, #4 should be off-cam. And vice-versa. Saves you the trouble of pulling the left-hand chain case cover.
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Several BMWs |
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06-28-2008, 08:17 PM
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Join Date: Jan 2006
Posts: 174
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WIL,
If you have the TDC mark and the Rotor pointed at #1 Dist cap, the engine should be on Compression, or the 2 Valves on #1 cylinder should be closed (compression) and the 2 Valves on #4 should be open (overlap). Easy way to check at home is to get a small tube and blow air down the #1 spark plug hole. If it blows out the exhaust your 360° out. If it has resistance, your on the correct stroke. Still may be off on the correct timing, but this way you know your on the right phasing. Another way if you haveaccess to compressed air is to do a leak down test. Some tester come with a whistle that will make a noise if the cylinder is on compression. |
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06-29-2008, 09:35 AM
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