911 sodium ex valves

[tunehall garage]

Hi, I am in the process of replacing valves in my Porsche 911 2.2, the car has been in storage for 20 years, I am now starting work on restoring it, I removed the low tension coil lead so it would not fire up before all the oil galleries and bearings were pressurized , I then decided to see if it would fire up, it fired up on one or two cylinders, about a thousand rpm but no more, and within 3 secs seized, I turned back the engine through the crankshaft nut about half a turn which was quite free turning, but on clockwise rotation would stop in the same position every time, my theory was a sticking valve, probably rust on valve stem, cam powerfully enough to press valve down but spring not powerfully enough to quickly return it to its seat, cranking the engine on the starter motor could only turn engine slowly giving a lazy valve enough time to re-seat, but the minuet it fired the piston speed increased exceeding the speed of the valve, on strip down I found that the valve head had parted company from the stem, this was due to corrosion from sodium filled valve stem, on further inspection only a sliver of clean metal was holding the valve together, there is traces of a white substance which is probably the sodium, so I am now going to replace all the ex valves so it will not happen to the other 5 valves, hope this is helpful for any one else who may be about to start a long time stood engine, regards John (Tunehall)