Fair enough - I suppose PZ's question about modifying it for 2 valves was very open-ended.gruntguru wrote: ↑16 Jan 2018, 13:46Nothing in the discussion led me to assume that, rather I assumed the simple case of two springs for two valves vs one spring for two valves.
If you want to compare 2v to 4v heads on the same engine - OK the lift will reduce somewhat (not halved because valve diameter won't halve) and of course the valve mass will reduce (significantly since mass is proportional to somewhere between the 2nd and 3rd power of the valve diameter) - all-together a very complex proposition to try and make assumptions about.
Well coil springs are only loaded in shear unless coil clash occurs in which case there's high herz stress. There shouldn't be significant bending stresses in a coil spring.(unlike coil springs) the above types avoid the combination of substantial bending and torsional loads
With a torsion spring, the outer shaft will be loaded in both torsion and bending.
I am sure it's the other way around - the combination of torsion and bending is worse in a torsion shaft spring