308 stuck valve?

I am in the middle of doing a major service on my 78. When I put my new set of timing belts on, with everything lined up, I cranked the engine to tension the belts. Unfortunately, either the tensioner spring did not deploy or the tensioner nuts were not loose enough so the belt slipped considerably. The engine wouldn't crank further because of the extended valves, so I disconnected the cams (by that I mean I loosened all of the cam cap nuts so that the valves all close). After this, the engine cranks further, but still stops
(hits a valve).
I followed this by removing all of the cams as well as the "buckets" that the shims sit in. The foward bank valve assemblies look even, but on the rear bank cylinder #1 exhaust valve sits higher than the others and can even be "lifted" a little higher (!), while the #4 exhaust valve sits a little lower. I don't think the valves are bent, as I only cranked the engine gently by hand. So I guess the question is, how can a valve get stuck and has anyone ever "unstuck" one before? I am really trying to avoid head removal even though it's the rear bank which won't require pulling out the engine.

 

Yeah I've already tried tapping on a block of wood on top of the valve spring, but nothing. The strangest part is that after tapping, the exhaust valve on cyl #2 came up just like #1 and I was able to take the springs out of both almost by hand and lift the 2 valves about a half inch higher than the usual height. To make this story even stranger, the engine had 200+ compression on each cylinder before begining this work and ran like a champ, so I have my doubts about excessive wear.
The stoppage occurs at near TDC making it either cyl #1, 4, 6, or 8. Intake valve on #1 looks slightly lower as does exhaust on #4, but no success on tapping them free. I'm looking for other possible solutions before taking off the heads.
Vince

 

When I replaced the shims for my valve adjustment, I was not able to measure if the clearance was correct, since I couldn't turn the crank to measure with the cam lobes pointed up. It is conceivable that if I was off in my clearance measurements and that I could have put in a shim that was too thick. Even with the close valve/piston interface of the 308 engine, I am doubtful I could have bent anything this way, because if I was off, it couldn't be by much. I have the cams off now so it shouldn't matter unless something is stuck or bent. What would be the clearance between valve and piston?
Vince

 

I'm thinking the valve seal is sliding up somehow. If the valve had snapped, I'd probably be able to slide it out completely since they almost always break at the thinest part.
You are right though, I need to pull the head, hopefully only the rear one. What's a head gasket go for these days, $200? I take it that no one has actually ever been successful in re-using one?

 

When I said I cranked the engine, of course I meant manually! This is not my first time doing this, but I do feel like an idiot.
I was able to pull off the rear head tonight in a couple hours. It was alot easier than I remembered. Kudos to Steve King, you guessed it first. I had not one, but two broken exhaust valves. The engine cranks (yes, I mean manually) fine now so I'm pretty confident in the foward bank. This shouldn't be a big job, but who would have thought this could happen when cranking manually. This certainly is the first time I've seen it. Let that be a lesson to all of you!
In the past I've always sent out my heads to be done. I take it that once I slide the new valves in, I will need to acquire the Fiat/Alfa spring compressor? Any tips on assemby?
Vince

 

This is a pretty low mileage engine, so I'm going to look at my options before commiting to a head rebuild. Funny you should mention sodium valves though. I completely forgot these were sodium filled until I was washing the broken valves and they started heating up and singing: "snap, crackle, pop"!
Thanks for all the suggestions.

 

Yes I am back in the Ferrari game with my third one, a 78 308 GTB. Haven't had much time for this with 3 kids (yes, three now). The last time we spoke, you were thinking about putting yours up for sale. Did you ever make it to Italy or Villa San Giovanni for that matter? Anyway, e-mail me at [email protected] so we can catch up.
Vince