I purchased the timing tool for my N12 once I discovered I only 2 in of vacuum. Hoping this was related to the cold start rough idle I decided to verify my timing. Once the crank pin is in and the halves of the cam holders are tightened, there is clearly a gap between them. The screw to lock the halves together won’t start unless the halves are loosened—and even then the intake cam lock pulls/warps downward to become flush with the exhaust.

It appears i am I am out of time—would you agree?

Exhaust jig tightend

I take jig tightend

Gape between the halves when tightened

Gap when halves are tightened. Bolt will not start u less they are loosened

 

Here is a video once the Cyrene bolt is tightened then loosened—you can see the stress it’s putting on it to have it tightened

 

You are in that place where it is time to replace the timing chain, guide rails, lower sprocket and if you have very high mileage maybe worth doing the oil pump chain at the same time. There are loads of guides of how to on Youtube. Chains kits are available and one post recently pointed in the direction of a good kit in the UK (if that's where you are) from Neo Brothers.
Replacing the front crank shaft seal is also part of this routine. While you are in that area consider the age of the water pump and if it is still the black plastic one, get the newer uprated metal one. Auxilliary belt too.