The original valve stem at the rear comes with 2.5mm.
With 4mm up to 170bar not good results here.
With 3mm at 140bar didn't lock open and less hammer was needed.
3.6mm is waiting for o-rings to arrive.
More testing in the future.
Just to summarise the valve testing and to put an end in using rallyshark full beans thread i can say a valve shaft of 3.7mm is about the more balanced you can go with a maverick valve and only if using a valve return spring with preload close to the original one.
Just for sake of completion i must say all the different valves i tested at beginning were using a 6mmOD and 0.3mm thickness 316L wire so they couldn't be directly comparable to the original because i was already introducing a change that worked well with the original valve but was creating a problem with the more balanced ones-- being not enought preload to close the valve back if little pressure was behind it causing valve to blow open temporarily.(not enough energy in the spring to overcome o-ring stiction on it's own).
The original valve return spring solved this though I'm still using a weaker one at the moment but i still use an adjustable one like the impact.
Needed around 5mm hammer pre-load for 170bar pressure with 800mm .25 barrel but there are drawbacks to using this type of valve experience by me and said by others.
@nervoustrig recently posted something that matched my testing and that i couldn't put so eloquently in words. Big thumbs up for this guy, for everything i have red from him, he knows his stuff and says things to the point.
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"A balanced valve does not produce more power at lower pressure. A balanced valve is simply easier to knock open…easier to develop a given amount lift and dwell with a lighter hammer and/or spring. This advantage comes at a price, however. Relative to a conventional valve, balanced valves are more sensitive to inevitable variations in hammer strike, more sensitive to pressure variations related to regulator linearity and temperatures changes, and more susceptible to a slow first shot due to O-ring stiction (breakaway friction of the O-ring which seals the balance chamber).
As such, I am of the opinion that a balanced valve is best suited for energy levels somewhere north of 100fpe. In that role, they really shine. For everything else, a conventional valve is hard to beat for its simplicity, tuneability, reliability, and consistency."
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The point of this testing was to use less hammer so that more flow area is available for larger calibers by not needing a thick valve stem around throat area. Done. Happy mostly with what I learned and that there are some people who have good info around this forum and are humble and patient enough to share.
