Cam reinstallation

At TDC on compression the exhaust valve should be completely closed on almost any engine I know of.
the critical point is generally 360 degrees from that at TD on the exhaust stroke when the piston is generally approaching a closing exhaust valve.
Could cam timing be off 360 degrees?

 

The reason Ferrari puts assembly marks on the cams is to prevent bending a valve stem while torqueing down the cams on reassembly.

 

An unknowing amateur can bend valves doing this. Some minor shift can will happen as you bring it all home progressively but you are not using an air tool ramming the caps down and ignoring the movement. As Taz says the marks tell you where you don't hit. Just respect them and work everything home and tweek shaft position as needed. You don’t try and lay shaft on and ram home 1 cap then put on the others. It is more of a progressive process.

 

Ouch... expensive lesson! If I were you I'd ask for a very long warrantee on that valve job.

I made a similar mistake once on my Lancia Fulvia, where on bringing home the bearing caps one of the valves touched the piston and it took me a while to find out. In those days I changed camshafts in the parking lot the night before a track day as it was my only car. Anyway, nothing bent or broken and off I went. Several months and two track days later, that valve broke, buried itself in the piston, smashed the head to bits, bent the conrod and ruined the crankshaft. While not a Ferrari V12, these old Lancia 1600 engines are getting rare and expensive either.

 

What Carl said. The job of reinstalling cams in these cars should be done with a quarter inch drive hand socket turning little bits at a time until there is enough tappet deflection to allow other caps to be installed. Watching the assembly marks as you hand tighten if you notice that the marks move a bit you can usually hand rotate the cam by gripping the cam gear and gently turning until they are back in line.