1978 911 SC Cam Timing

[RLM]

I just finished performing the cam timing per Wayne's book with a valve clerance in both cams of aprox. 1.02 mm (digital gauge). After obtaining the desired value in the right cam at TDC I noticed that both cam are oriented with the "930" mark facing upwards @ TDC.

1. Is this the proper orientation of the cams after finishing the process if conducted correctly?
2. Why is it instructed to preset gauge at 10mm before conducting process for right cam? Is it really necessary and why?

I will appreciate any assistance and clarification. Thanks in advance!

Rodney

[Flat6pac]

After timing the cams, on TDC#1 the cams will have the marks up both sides, that never changes. When the 930 is up on both cams, pin each one and measure the left bank on 1 revolution and set your number.
I dont know about the 10mm preload but you need enough preload to measure the .9mm to 1.1mm accurately.
Bruce

[Eagledriver]

Both cams should be oriented the same at all times (930 up, down sideways, etc.). The number 1 fires when the 930 is up and the number 4 fires when the 930 is down. So, when the 930 is up both number 1 valves are closed and the number 4 intake valve should be open to your setting (1 mm).

-Andy

[boyt911sc]

Originally Posted by Eagledriver

Both cams should be oriented the same at all times (930 up, down sideways, etc.). The number 1 fires when the 930 is up and the number 4 fires when the 930 is down. So, when the 930 is up both number 1 valves are closed and the number 4 intake valve should be open to your setting (1 mm).

-Andy

Andy,

You have explained it very well. That's how I keep remembering the cam orientation when doing cam timing. It would be also good if you included the distributor's rotor orientation (for example: SC's). Many had the ignition set 180° off.

Tony