I am replacing the head on my R50, and unfortunately moved stuff around and screwed up and didn't fully read some of the information on marking the chain and not letting it fall into the block. I am now trying to get it all together as if I am assembling the engine after a total rebuild, and have looked for instructions on timing the cam in this case. I have been disappointed in the lack of information.

I have looked on the forums (this one and others) for the procedure to time the cam from scratch, and am frustrated at the lack of full explanation on the procedure as if I were assembling the engine after a total tear down. I have a Bentley manual (lot of wasted paper in my opinion) and am not satisfied with the information there either. I downloaded the workshop manual from a NAM post, and it is not much better than the Bentley manual. From those and various posts I have gathered this as an alignment procedure:

1. Rotate the crankshaft until the piston tops are at an equal depth from the top of the block, and the mark on the crank pulley is at engine 12 o'clock. (There are two marks on my pulley and one of them appears to be at 11ish with the other at 12). This is interesting to do with the engine in the car, and a dental mirror to try to see the mark with.

2. Rotate the cam until the triangle mark is at engine 12 o'clock.

3. Put the cam timing fixture on and torque the cam sprocket bolt down.

The question I have is to confirm my assumption that the timing chain guides need to be in place, and that the timing chain tensioner needs to be installed also. Is this the case?

During this procedure I have the rockers backed off so I can rotate the cam without a lobe on a rocker arm jumping from the spring tension.

Anything I am missing?

 

I successfully pulled it off. The procedure I used (as if starting from scratch from a total tear down) is as follows:
1. Rotate the crankshaft to get the pistons at the same depth off the deck of the block, and the crankshaft pulley with one mark at engine 12 o'clock, and the other at 11 o'clockish.

2. Get the cam sprocket at engine 12 o'clock with the chain on. I takes some playing with to get on the right teeth.

3. Get the chain guides and tensioner in place.

4. Rotate the cam to line up the locater dowel with the slot in the sprocket.

5. Position the cam sprocket with the timing tool.

6. Torque the sprocket retaining bolt.

7. Torque down the rocker shafts.

8. Remove the timing tool.

9. Button up the engine.