308GT4 top end rebuild

ferrari 308 gt4

I am about 80% through a top end rebuild of my 308 engine. I have removed the heads, replaced the sodium filled exhaust valves that fell to bits while I was taking them out!
Played around with lots of shims to get the inlet and exhaust lash just right. New Elhring head gaskets new seals and O rings. Rebuilt carbies. Replaced the cam sprockets with billet alloy ones from super performance. I was squirming at the price of these sprockets but one of the original plastic ones lost its rim. perhaps it's good insurance.
Anyway the blog link above tells the story so far.
I invite all comments/ suggestions/ questions.

 

Good work! Valves are going to be a big topic. Which valves broke? Do yo know the cylinder #? There is a theory on poor cylinder cooling. Was there excessive corrosion in the cooling system anywhere?

 

Exhaust Valves 5 and 6 I think. The main corrosion problem was the 20mm threaded aluminium connection in the water pump housing. Completely blocked up.
So far the biggest problem that I can see with these cars is the sodium valve weakness and the cam pulleys. If either goes the engine will start making ugly noises. I am glad I pulled it apart. It was very tempting to just do the belts and oils and go for a drive.....

 

Thanks for the info. How were the other exhaust valves? Have you tried to break them? Reason I ask is there is a theory spot over heating is making them brittle. If only 5 & 6 are bad and the others strong this may be the case.

 

George,

You stated " The main corrosion problem was the 20mm threaded aluminium connection in the water pump housing."

Is this the feeder line from the tank just below the thermostat housing?

 

I did not try to break any more valves. I still have them but I don't know which is which. Just to add some factors to your hot spot theory: mine is a euro spec engine, no air Pump. The 5 and 6 valve seats and the combustion chambers on 5 and 6 did not look any different to any of the others. I would imagine the air pump engines would run hotter and am very suprised that when I see cars for sale there is never any mention that exhaust valves were replaced. I am astonished that these cars are still running. My engine has only done 48k miles .

Yes the feeder line below thermostat housing there are 2 threaded inserts that look like they are a part of the housing A 20 mm one and a smaller one.

 

While the engine is out, it is very easy to remove the LSD and turn around the friction discs to expose the unworn surfaces to the cross plates. Functionally a new LSD for very little effort. Nice looking work with the engine.

 

Thanks 911308. I will look into that