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gtc gtc is offline
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Join Date: Nov 2006
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Cam timing sanity check

After getting my cams timed nicely, checking my valve clearance, and installing my rockers, I got little ahead of myself and installed the tensioners and sealed up the chain boxes.
Now when I'm adjusting the valves, it seems like the right hand cam is off by one crank revolution, as though 1 and 4's valves are both closed at #1 TDC.
Could I have somehow rotated the right hand cam 180 degrees? Am I missing something obvious? Can someone tell me which way the #1 and #4 cam lobe should point at TDC?

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Graham
1984 Carrera Targa
Old 04-06-2015, 11:11 PM
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The cranks turns twice (720 degrees) for the camshaft to turn once (360 degrees). So you have a TDC for cylinder 1 in ons turn and in the next turn it is for cylinder 4. When cam timing is done correct you have closed valves (rocker is able to move) at ingition TDC for one cylinder and rocker is tight at overlap TDC for the other cylinder. So both valves should not open at same TDC. You are probably of 180 degrees on one.
Old 04-06-2015, 11:59 PM
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When you're adjusting the rockers, you're on the back of the cam lobe (including visually). If you're right, one rocker either 1 or 4 has started to move as the opposite doesn't for nearly 300 degrees of crank turning.
Bruce
Old 04-07-2015, 12:59 AM
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Argh. I guess I'll just have to take a fresh look. Frustrating after being so careful to get the timing process correct.
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1984 Carrera Targa
Old 04-07-2015, 06:50 AM
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Sure enough, the cam was 180 off.
I was misunderstanding the instructions, and rather than just move the crank a few degrees to the next TDC after I reached the set point, I rotated it 360 + a few.

Obligatory progress shot:
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Graham
1984 Carrera Targa
Old 04-08-2015, 08:59 AM
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911 2.2 T targa
 
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Looks very nice!
Good that you corrected before damage was done

Old 04-08-2015, 11:02 PM
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