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Valves
I am sure that there are many strong views on the parts used in 911 Valve Trains and I would like to try to canvass some opinions into how to make some reasonable improvements. I am particularly interested in increasing engine revs to 9000+ on early 2.0 engines.
VALVES
Early Inlet Valves seem relatively straightforward and are just a bit heavy due to the 9mm stem.
I understand that quite a number of modified engines now use 7 or 9mm valve stems to save weight .
This may be an issue with FIA engines as strictly changing valve stem diameter isn’t quite within the regs.
Has anyone tried Hollow Stem Valves of even Titanium as a means of saving weight.
Early Exhaust valves were Sodium Filled and are supposed to conduct heat more successfully and they are substantially lighter.
I am not sure when they stopped using Sodium Filled valves .
Again using Hollow or Ti valves could means weights will match the stock valves.
Using either Ti or a hollow valve will reduce heat transfer from the valve, particularly when compared to a sodium filled valve.
Does anyone have experience with hollow or Ti valves to see if this is an issue.
VALVE LOCKS
3 groove keepers seem to work well but they do not clamp the valve.
When fully installed the valve is still free to rotate and this now seems to be non-preffered and many competition engines use single groove locks which fully clamp the stem of the valve and prevent rotation.
Any practical experience would be useful.
Hollow Valves
These seem more likely to fail due to increase stresses but the manufacturing route is similar to Sodium filled valves which don’t seem to have problems.
Titanium Valves look positive but Ti is not great in environment where it can fret.
It looks as if TI are valves are commonly coated in either DLC, Titanium Nitride or Chrome Nitride.
Does anyone have experience of the different coatings? I would be tempted by either TiN or Titanium carbide as DLC is just too costly.
Valve Springs
Has anyone tried Beehive Valve Springs as a way for eliminating valve bounce with a lightweight spring ? They seem like a good idea but may not be practical.
Any data/comments welcomed.
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