Cam Timing 930 symbol both sides up or not

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I am a bit confused by the instructions in the Dempsey How to Rebuild and Modify 911 Engines book. And it seems to contradict what is written in the Bentley manual. The description starts describing the left side by saying the 930 symbol should be facing up on both sides. Then the left side is timed. Then you rotate the engine 720 degrees. So now both sides the 930 symbol should face up again. On page 166 it states that after rotating the engine 720 degrees you should be at the right location for timing the right side. But then on page 167 it is stated: "The basic process for timing the right camshaft is very similar to the left side from this point on. Confirm that the camshaft dot, 930 mark, or keyway is facing downward (the same way the left side is facing).

Should that have said: "...is facing upward (the same way the left side is facing)???

At any time both, right and left cams are always either both up or both down, but never 180 degrees off. Correct? Thank you.

[bumble]

There was quite a good discussion on timing techniques a little while back - see:

Cam Timing Question

[snbush67]

At any time both, right and left cams are always either both up or both down, but never 180 degrees off. Correct? Thank you.

Correct. That is with 930 Cams. With some aftermarket cams made from billets they have dots which may or may not be 180 degs off.

cam timing

Shane

[2.70Racer]

To answer your question, with stock cams, the keyways and marks are both straight up or straight down at Z1.
The exception to this rule was my Solex cams from "the camgrinder" John ??
He marked them so the marks were opposite. Live and learn.
Typically the 930 mark or keyways are both up at the same time, when the engine is at Z1.
This is the initial starting point. #1 will be at the compression stroke and #4 will be at overlap.
Now you look at the intake and exhaust cam rockers on the left side, (cylinders 1,2&3).
Both intake and exhaust valves will be closed, this is the compression stroke.
To set the left side you will need to rotate the crankshaft exactly 360 degrees to the next Z1.
At this point the #1 cylinder intake valve will be just beginning to open.
This is the overlap position referred to in most cam timing instructions.
While in the overlap position for #1 at Z1, look at #4. You will notice both valves are closed.
This is the compression stroke for #4.
Turn the crankshaft 360 degrees clockwise to the next Z1, always clockwise.
Now you will notice #4 is at the overlap position and #1 is in the compression stroke.
You'll also notice the 930 mark, and keyway on both cams are straight up.
The idea to always remember when timing cams is #1 fires 360 crank degrees from #4.

[snbush67]

Doug,

Same issue with my Cams from Cam-grinder. Really made life fun for awhile. I had some serious head scratching moments. It wasn't until I looked at the stock cams compared to the DR Cams from billets that I figured out the dots in relation to the lobe orientation.

Shane

[ChrisBennet]

As a sanity check, the cam/dots should have the same orientation on both sides when you're done setting the timing i.e. if the left cam dot is at 1 o'clock the right cam dot should be at 1 o'clock also.

[efhughes3]

Emphasis: after timing LH cam, you only rotate the crank 360 degrees to get to where you'll time the RH cam. 720 degrees of crank rotation will bring a cam back to where you started, and is used to double check your dial indicator reads the same.

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Thank you everyone for assistance and valuable comments - as usual. Indeed I did get it wrong and that's why my engine did not start up. Now I think I got it and the engine will go back in next week some time. Here is where you find some more background on this story:
911 3.2 to 3.4 conversion; engine not running

I thought I post this thread separately as it is fairly generic and can help others that look for this info.

Thanks again. I think I am good now.

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To also take the distributor rotor into the picture. When I have both cams with the 930 mark is pointing up on both cams, the ignition rotor tip points to the cylinder 1 mark, the Z1 mark on the pulley points up.
Then when I turn the crank 360 degrees, both 930 marks will point downwards, the Z1 mark on the pulley is at Z1 again, the distributor rotor tip points to cylinder 4. Now when I advance the engine past 360 degrees from here, the intake valve for Cylinder #1 opens. Correct?
This also makes sense with the cam timing instructions. As when you start at 0 degrees (Z1 mark up, TDC, both cams 930 mark facing upwards) the intake valve start to move (open) after one full crank rotation (360 degrees).
Describing the process with just the TDC is a bit confusing since it is not clear what TDC it is referred to (intake opens up or compression stroke with overlap).

[efhughes3]

You are correct. TDC is typically when dizzy points to #1, and both valves are slack, when adjusted to .004" clearance.