[2.7RACER]

Mark,
Andy has provided a great overview regarding cam timing.

Let's review exactly what you are trying to accomplish.

You want the intake valve to open as the piston has reached the top and has begun to move towards the crankshaft, some might call it down.
With a Porsche motor it is toward the center of the motor.

Typically the valve begins to open anywhere from TDC to as much as 30 degrees before TDC.

This intake stroke begins at a point called "overlap" or "crossover"

The piston has just reached the top of the cylinder, completing the exhaust stroke. At this time the exhaust valve has just closed and the intake valve has begun to open.

This position is referred to as Z1 TDC overlap or crossover. This is not the same as Z1 TDC compression.

At the Z1 TDC overlap position the intake valve is just beginning to open.

This provides us with a measurement we can read with a dial indicator of just how much the cam has opened.

Typically it is at the beginning, just beginning to run up the lobe of the cam.

Depending upon the specific cam, the number you are looking for can be anywhere from 1.0mm for a cam that has only opened 1.0mm at this point to as much as 4mm or 5mm for a cam that has opened several degrees before Z1 TDC overlap.

Cam specifications are given in crankshaft degrees relating to Z1 TDC overlap.
The trick is the European cams are spec'd at 1.0mm open.
That is the valve has already moved 1.0mm (0.0040").

So a cam that is spec'd at 4 degrees BTDC has really begun to move around 24 to 26 degrees BTDC, but it hasn't reached 1.0mm open until 4 degrees BTDC.

Remember 1.0mm is only 1/25th of an inch.

So you set the dial indicator on top of the flat portion of the spring retainer when the rocker is riding on the back, (base circle), of the cam.

As you rotate the engine (clockwise only) you want the lobe controlling the intake rocker to begin to move the rocker as the motor is reaching Z1 TDC overlap.

At Z1 TDC overlap you want the dial indicator to read 1.3mm, 1.5mm, whatever the spec is for your cam.

If the dial reads low at Z1 TDC overlap you need to advance the cam.

If the dial reads high at Z1 TDC overlap you need to retard the cam.

If you are working on cylinder one, The "dots" or the "numbers" or the keyway will be pointing down on the leftside cam.

When both sides are done, both cams will point down at Z1 TDC overlap for number one cylinder.

Conversely when you are at Z1 TDC overlap for number four, the right side, the "dots" or "numbers" or keyways will both be pointing up.

This is where you want to leave the motor, because this is also Z1 TDC compression for number one. So when you install the distributor, have the rotor pointing at number one, about 3 o-clock.

This is just one way of describing cam timing.

Do a search on "cam timing"

There are many people that have described this procedure.

There may be one that makes it all clear.

Once you have done it, you'll wonder why it seemed so complex. It isn't.
You are just timing the camshaft to the crankshaft.
Have fun,