cam timing photos (need review)

[SchnellSchweitz]

Ok... I am not sure I have this timing thing down and would appreciate some outside input on my work.

One of the issues I am not sure I understand is the relation of the cam keys to the Z-mark. Everywhere I have read says all three should be straight up when the chains are installed. However, I made adjustments to the cam to set the timing. This has changed the key-to-Z-mark relation completely.

_____________________________

The following pics and info describe my current status for the #1 intake only (3.0L/'82). I hope this will make sense to readers.

1) Z mark-to-case-split is set to exactly 1 ccw dial gauge rotation (-1mm).
The intake is beginning to open at this stage.

2) After 1/4 cw crank rotation past the case split, the dial gauge has unloaded 10.415 ccw rotations (-10.415mm).
The intake is fully open at this stage.



3) After a .4 cw (approx) crank rotation from the last stage the dial gauge is back to 0.

The intake is fully closed at this stage.


4) From the last stage, it takes 2.35 cw rotations (approx) for the process to start again at stage #1.

Does this sound correct?

Thanks in advance for you help.

Eric J.

[lindy 911]

With #1 piston at TDC the "Z" mark will line up with the case split. At this point in the cranks rotation, the intake valve should have just started to open. How much it should have opened at this point is the measurement you are looking for. So with the piston at top dead center for #1, the intake valve should be open _____mm. Fill in the blank with whats correct for your motor. If, when the crank is at TDC, you don't read the value on the dial indicator you should adjust the cam so you do. It's really very simple. Don't over-think it.

Lindy

[OldTee]

My suggestion: Get another Z block and buy two digital dial indicators from el cheapo Harbor Freight. Then install #1 and #4 intake rockers.

Then adjust #1 rocker to .003 lash. Rotate crank 180 degrees and adjust # 4 to .003. Then go thru the adjustment proceedure in the book. Using two digital dial indicators can give you a pretty clear picture what is going on.

[Flat6pac]

Youre not interested in what happens after 360 degrees but just @360 is the cam timing for the left cam where you start with all 3 marks up. Pin the cam at the spec for your engine.
720 degrees on the crank will proof the setting.
Move your dial guage to the right #4 and crank 360 degrees and pin the spec number. Turn 720 degrees and proof your spec.
both cams need to be pinned when you start at some close to spec number.
Bruce

[304065]

Nice Kaefer gauge. I have a few but I did use a pair of digital Mitutoyos for the task. Doesn't matter though, an analog gauge is fine, it's just harder.

Photo 1. When you say, "the intake is beginning to open at this stage," that is a good sign that you have the cam in the right starting orientation-- overlap TDC with 0.1mm valve clearance (the "timing point.") If the intake weren't opening, that would be a sign that the cam is 180 degrees out of phase (if the intake valve clearance can be felt, then the cam is on the base circle which means you are at compression TDC)

However, you say the gauge has unwound 1.0mm from the starting reading, that is not the timing spec! Timing spec for a stock SC is 1.4-1.7mm, you want to split rhe range and time the cam at 1.55mm! So you need to lock the flywheel at Z1, turn the cam until the indicator reads 1.55mm, and then tighten the cam back down.

The fact that you turn the crank and you note that the valve cycles is good, but that information is not relevant unless you are trying to map the lobe profile. What you care about is only ONE point in the cam's rotation, that is, the valve lift at the timing point.

[304065]

I didn't answer your original question- when you start the process, both dots are up on the cams and the crank is at Z1 (TDC cylinder #1). When you turn the camshafts to reflect the cam lift at the timing point, they rotate with respect to the crank pulley. How far is a function of the lift setting of the camshaft, but that's simply an observation, not a measurement-- the actual measurement is performed at the valve.

[SchnellSchweitz]

Thank you all...

I especially appreciate 304065's information. It looks like I was going off the wrong "intake valve overlap" number from Wayne's book (i.e. 1mm).

The 1.55mm measurement he provides is for the 930/03/13/07/08/09/19/16/17 "model."

I'm going to ask a "bone head" question here... are these case numbers? My case is 930.101.103.4R. I'm assuming the "03" in the list above is for my case???

Thank you.

Eric J.

[Flieger]

No, these are type numbers. There is another stamp on every non-replacement case. 911/83 is the 2.7 RS spec engine. I believe it is in the general area of the *star* engine number.

[SchnellSchweitz]

Oh... I found it! I have a 930/16.

Thank you.

Eric J.