MRod .25 cal Valve Mods

[PakProtector]

So about 75 FPE....

Bob

I used 75.5 as the average. Is a velocity curve quite similar to your green DD .30 curve.
cheers,
Douglas

[TEC]

So who supplies power junkies without valve modding skills a nice upgraded unit?
I am itching to try something like this.

[PakProtector]

So who supplies power junkies without valve modding skills a nice upgraded unit?
I am itching to try something like this.

The full job would take a bit more than just the valve. Up to what I have done can so far is just the valve( with the exception of a .165 barrel port on the 24" BSA barrel )...so perhaps see Lloyd.
cheers,
Douglas

[joel w]

What do you guys think about discarding the inlet plug all together and just drilling a 1/8"
hole all the way through the valve body so you could compress the spring and slide in a 1/8" pin to retain the spring at the correct distance? One could grind a flat side in the middle of the pin for the spring to stay in place?

Like this.

Edit: I might have to cut in another oring groove on the backside of the pin to keep air in?

[rsterne]

You would definitely have to cut another O-ring groove as drawn.... unless you drill the space between the existing O-ring groove and the end of the valve (1/8") and use a thin pin.... A 1/16" steel pin would be strong enough.... but you still have to figure out how to locate the spring on it....

How much area do you figure you need on the inlet side of the valve?.... I already have 3 times the outlet area.... If you were dealing with a regulator in the way and needed more plenum volume I could see doing it, maybe....

Bob

[joel w]

It looks like there is enough room for an oring groove after the pin and before the breech screws. I might be able to make a stand off that the pin slides through for the spring to sit on, like your idea  but I think it would want to try to rotate around the pin and bind up on the side of the valve under pressure? edit: (or use a longer spring.)

I am going to be running a Huub vented regulator into an opened up gauge block, into the valve pushing a .22 pellet and probably eventually with an air tube extension.  I am not really a numbers guy so I was just going for big and easy.   

Looking at what you and LLoyd did, this looked easier to me and seemed like it would flow well with more (maybe not more) plenum space?.

edit again,  One could make a spacer that fits on the valve head to hold the spring to makeup the difference in length?

[rsterne]

Just use a longer spring....

Bob

[PakProtector]

Joel,
I can't escape thinking the spring will jump out around the pin and valve body. Also, the bolts that hold the reciever to the air tube are too close together to allow you to bore the ID so large. With the Marauder valve a big flow impediment seems to be the sharp turn to the exhaust port right behind the seat. If you can move the seat forward by ~3/16" you can andle the port by 20 degrees from its vertical, OE configuration. This seems to help a great deal.

For your 22 cal, I'd suggest a .234" throat, and an angled .165 exhaust, a .165 poly transfer tube, and a .165 port in the barrel. If you want to get really nuts, a slightly bigger throat, and a 3/16" exhaust to go along with an oblong ( a slot in the barrel )barrel port will enable some serious power and require heavy slugs. Without going past .165 round barrel port, you should be able to achieve 60 FPE with the heaviest pellets...and at reasonable efficiency to deliver a full magazine worth of low-velocity-spread shots.
cheers,
Douglas

[joel w]

Thanks Bob..

 Douglas,  That drawing was not to scale or anything and I had no intentions of opening it up bigger than the breech screw depth (1/2") if even that.  Just trying to get rid of the inlet plug restriction easily and give you big bore guys some other ideas.  Thanks for the advice..   

[PakProtector]

Thanks Bob..

 Douglas,  That drawing was not to scale or anything and I had no intentions of opening it up bigger than the breech screw depth (1/2") if even that.  Just trying to get rid of the inlet plug restriction easily and give you big bore guys some other ideas.  Thanks for the advice..   

Whilst playing with a stock config, bored valve I re-installed a stock valve body cap and got no drop in performance while running in the 85 FPE neighborhood. I still modify the cap, but I can't excape the conclusion that it matters very little, and efforts should be spent elsewhere.
cheers,
Douglas

[joel w]

Thank you sir, that is helpful!!  My goals for this .22 are modest fpe and more about the flat string,  shot count, and education.  Then go nuts on the next one...