To get anywhere close to the accuracy needed to measure cam timing, you really have to measure the piston position and valve opening distance. While there are 'timing marks' on the washer in front of the front cam tower, that v-notch is approximate and useful only for ensuring the cam is not a tooth off when installing the chain.

I used to do this job regularly on my Masseratti 4 cam engine. Each cam could be adjusted in 0.5 degree increments. I used a machinist steel tape to etch marks every 2 degrees around the flywheel to position each piston at TDC precisely. Then the piston had to be moved so many MM down (either in direction of rotation or back, depending on whether intake or exhaust cam, measured to 0.1 MM) and measure valve stem depression (measured to 0.01MM ) at that point. Goal was to get cam timing exact, and valve lash precisely uniform. There were 'timing v-notches' on the cams, but the closest I could ever get using those was about +/- 5 degrees of correct cam timing. That's A LOT on that engine.

(Only with everything uniform would it idle smoothly and also perform @85Hp/l @5000 RPM) Just had carbs and centrifugal ignition timing advance, and as a free breathing hemi-head, was real dirty exhaust at idle, but delivered very good economy at cruise.