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Hello,
I was pricing out an engine rebuild for a 1967 911S and I was shocked to find that Pelican Parts sells exhaust valves for $98.00/each.
Why are exhaust valves so expensive? Is there a cheaper solution? I have read that you need to replace the exhaust valves when doing a rebuild, why?
Thanks,
Evan
If the exhaust valves are not worn you shouldn't have to replace them. They wear on the stem (smaller) and the valve face (the part that contacts the seat). However, the face can be reground within reason. The valve tip can wear as well.
Some of the early exhaust valves are sodium filled. That is, the valve stem is hollow. The sodium within promotes better heat transfer from the valve stem to the valve guide. If the exh. valves are sodium filled, they will cost more than other exh. valves. Not sure about your 911. You can always shop around and look for the best deal or have a machine shop examine yours.
Sherwood
The exhaust valves on the '67S 901/02 engine were definitely sodium filled. That's why they are so expensive.Quote:
Originally posted by admin
If the exh. valves are sodium filled, they will cost more than other exh. valves. Not sure about your 911.
So what's your feeling about the durability of the valves. On the PelicanParts site (best porsche parts site I've seen) they say to replace them when doing a rebuild, that seems a bit excessive.
If the engine is undergoing it's first rebuild, and the valves are ok, do you see any overwhelming reason to replace?
Grab a micrometre, If the stem is under size, it HAS to be replaced. As well as the guides most likely. Opt for the sodium. They are better and much lighter for better revability....
It's all part of the cost of playing with Porsche's. Still cheaper than some other exotic machinerys or Audi's :-)
Rob.......
Most of the earlier cars used sodium filled exhaust valves. The sodium is a solid at room temp. and undergoes a phase change which takes a lot of heat away from the seats. ~$100 is the going price. Be glad that you don't have to pay that for the intakes also, as I recently did. The 993 RS uses sodium cooled intakes and exhausts, the bill from Andial was ~$100/valve
All '72 used sodium in the exhausts, I think that starting w/ the 76 C3 the sodium was no longer used except on turbos. It was then reintroduced on maybe 964 but definitely 993 for both I & O. In the 993 the intakes are sodium cored more for weight reduction than cooling, those valves are big.
914's uses those pricey little buggers also, but of course you only have to buy 4.
correct me guys, but the sodium goes from a powder straight to gas phase.
Na. is a solid metal @ room temp. but melts @ 97.8°C & 1 bar and boils @ 552.9°C & 1 bar. If your engine gets that hot you have bigger problems than boiling Na.
An aside, it is not a good idea to cut the valve apart to see if it is Na cooled.