Hi, I have been told my 308 GT4 has hollow sodium filled valves - and they need to be changed ASAP. The car has done 70k miles and apparently this is about the time that they snap. Has anyone else "HAD" to change the exhaust valves?
I'll let others answer your question, but sodium-filled exhaust valves are not uncommon. Volkswagen 16V engines from the 1980s have them. VW was kind enough to make them non-interference, though the intake valves on the same engine ARE interference.
I had Sodium valves in my GT4 when it had about 70K miles and had them replaced with stainless when I had the rebuild.They looked ok to me but looks are nothing.There have been numerous discussion on this topic in past threads but I can't recall anyone ever having broken a sodium valve whilst there engine was running.I think I read that while someone was replacing there valves and had a sodium valve in their hands when it fell on the floor and broke at the top of the shaft.I'm sure their will be others that will chime in on past experiences.The only thing is when you have an engine with 70K miles on it and you are replacing the valves and guides is do you go all the way and do the rings and pistons as well?The engine has to come out and heads have to come off so do you go the full nine yards and do the lot or where do you stop?I intend on keeping my car thats why I went for the full rebuild.It also gave me a chance to bump the compression up and replace the second gear synchro.I also have a Maserati Merak with the same milage and I had a blown head gasket.So I decided to do the valves and guides while I had the heads off but didn't want to do the rest in order to save money.A year later I have a leaking cylinder liner that is allowing water into one of the pistons and the engine is out again to replace pistons,rings and from what I'm hoping for is only the liner seal.So thats why I decided to go all the way with the GT4 so I can guarantee that I won't hopefully have anymore major mechanical problems.
IMHO if you are doing an engine rebuild, do a complete rebuild. Cheaper and more reliable to do everything at once. That said, if you can pull the heads and rebuild them without pulling the engine, and the bores look good and the engine held good oil pressure before you tore it down, then just rebuilding the heads is an option. Either way, I prefer to do it myself. I'm no expert, but I know I spend more time and effort than anyone I coud hire to do the job. Farm out the really technical bits like boring cylinders, but all the bolting-it-together bits: DIY!
I know of a fellow GT4 owner who is (or was, I haven't seen him post here in a while) a member here and one of his valves let go when out on a drive, taking out that piston and did a good number on his cylinder head. Very messy. Three of my valves were bent only and I was lucky to catch them in time. I replaced ALL exhaust valves with solid stainless. They bend/break because the guides wear-out. Replace those when replacing the valves.
Nick try below for the parts you need here in the Uk http://www.superformance.co.uk/download/Catalogue%20Ferrari308_04.pdf
First time i read such a think, normaly it goes the other way people are worried because their valves don't have sodium in it. Sodium is state of the art only better are nimonic with sodium but normaly not used in street engines. The sodium valves can handle much more temperature and stress befor they get damaged then normal steel ones. On high performing cars ecspecially turbo and kompressor engines without sodium you will have an problem after the first km. Normaly you only find non sodium exhaust valves in the cheapest engines with low performance because the manufacturer tries to elimates the mcuh higher costs of the sodium valves. But on an standard performing engine only aftermarket non sodium valves are available but with them you won't have fun long time. I would never change a expensive good sodium valve with a china simple full steel valve. We race sodium valves with 200hp on each cylinder of the engine and revs to 9000rpm with valves over 150.000 miles on it without ever damaging an valve. If theres an design problem with the stock sodium valves on the 308 i would change it to sodium valves wich are better not with crap. Ok the 308 has not much hp per cylinder and it could work long and the higher combustion chamber temperatures won't kill the engine but its no improvement. ___________________________ Samy
Just rebuilt my 308gt4 had 72K on it. The sodium valves all looked fine, but on closer inspection 1 of them had started to form a small hairline crack around where the neck meets the valve head..... it was only a matter of time! The biggest problem with my heads was that all of the original valve guides had significant wear on them and the valve seals were perished. If you are taking the heads off do it properly, replace all guides, seals and exhaust valves. I got all my stuff from Superformance/ Mike Elliot... very reasonably priced and helpful. Mike was even good enough to lend me the special tool they had made up for removing stubborn heads. If you take your time most of the work can easily be done by anyone with a reasonable grounding in mechanicals.
