Crosscut valve.

[Mike71]

Has anyone ever, or ever thought about making two valve halves, so one can make a perfectly smooth radius exhaust port instead of the factory 90* and a modified 90* to a slight angle, then solder it together and dill, bore, thread the rest of it.
Even if some solder gets into the exhaust port it's just a matter of a rotary tool to clean it out.

This would make the back wall of the port curved, that's where the biggest amount of air would hit, and even a modified valve still has the 90* edge in the back.. an engine intake port needs the opposite as it not worthy air in, an exhaust needs the long side curved.

Would be a good bit of work but I know alot of you go beyond basic work already.

Any thoughts  ? Sounds good in my head.
This is a thought on valves like the Crosman, Benjamin, paintball types.

[rsterne]

When starting from scratch, I simply bore my exhaust port on a 30 deg. angle, sloping forward from vertical.... The airflow then has to turn through 60 deg. just behind the valve throat, and then 30 degrees at the top of the valve where it meets the transfer port.... The lower corner, where the flow turns 60 deg. is close to the valve seat, so can be well rounded by hand with a Dremel.... I use a throat where the area (throat minus stem area) is 5-10% larger than the exhaust port and transfer port.... I use a flat nose bolt that retracts behind the barrel port after seating the slug (by using a "J" slot in the receiver) The barrel port can be made full bore area by making it 80% of the calibre wide and 125% long, and blending that into the round transfer port.... IMO the worst disturbance to the flow is the 90 deg. change of direction where the transfer port meets the barrel.... Here is an example....



You can actually see partially through the throat into the valve body through the exhaust port (RH photo)....



and two views of the barrel port.... Forward corner to be rounded with Dremel as in lower photo....





Hope that helps....

Bob

[Mike71]

Yeah even if the valve exhaust port was smooth and curved the air still has the bad 90* at the barrel, guess that would take away from any good a near perfect valve port would have.
And yes your from scratch valve has ALOT better angle over a factory one.
Are you seeing major improvements over a modified factory valve ?
I'm looking to mod a Crosman 362 valve myself, not going to worry about more volume but more so on getting that air out better than stock.
But was looking for a cutaway view of one (can't find a pic) and that vision got me thinking of the two halves so the exhaust could be milled at a perfect curve, though may very well not be worth it. My mind is bent anyways so I don't always come up with the best ideas.
But if I still had my shop I'd sure try it. Those days are long gone for me.

[rsterne]

Improvements are actually quite small, compared to getting the ability to flow up to bore-area.... Simply making the ports bigger, until they equal the area of the bore, produces the major gains.... However, to be truthful, the progress has been a process, and it's hard to remember which came first, the chicken or the egg....

MRod valves are of notoriously poor design, with a very small, vertical exhaust port very close to the valve seat.... This makes modifying them by angling or curving the exhaust port almost impossible.... You have to move the seat forward to accomplish either, meaning start from scratch, or bore out the valve and use an insert with the seat further forward.... 2260/Disco valves, on the other hand, have enough room between the seat and exhaust port to angle it about 20 degrees.... I started doing that long before I managed to figure out how to get to bore-sized porting, so it is now a bit of guessing to figure out how much of the improvement came from angling the exhaust port, and how much is from the larger porting.... Round barrel ports cannot be larger than 75-80% of the calibre or the projectile can be damaged when it crosses it.... Hence the use of oblong ports when searching for that last bit of power....

Bob

[Mike71]

I'm hoping to get a FT valve/Piston set pinned to the tube after I find someone worthy of me sending them my setup.
For now I'll mess with the stock one..

I seen the 367 build that Tack Driver 10 made the FT adjustable piston and a brass valve for. Now that's a setup I'd like to have. Well not sure if my wallet would agree tho.

[rkr]

When tuning .357 Evanixes we saw 40 fps increase at around 900 fps when we rounded out the 90 degrees turn at the valve tunnel. So yes, it does help a considerable amount.

[Mike71]

Unlike many of the modded valves you can buy, I am not wanting to open up the volume inside, would need extra pumps to build pressure again, I just want pressure and smooth transition of said air..
Now if I went .25 cal and or a longer barrel, then extra volume would help.

Just got my hands on a brass 13xx valve to rebuild and do a port job, got to be careful tho, these are getting very hard to find nowadays. Can't mess it up. Flat top and port job.. mod my trigger housing to bolt it in like the 13xx does..
All for a $100 pellet gun lol
Gotta love hot rodders mindset.

[rsterne]

rkr, I am not familiar with the Evanix, but if the porting is less than 80% of calibre, then any improvement in the porting can cause huge improvements in flow.... As the porting approaches bore size, such changes may not make as much difference.... Just my experience, YMMV of course.... Rounding any turns on the inside corner does, indeed, improve the flow.... Unfortunately, in some valves, the exhaust port is so close to the inside rear of the valve (where the seat is), you cannot do that to any effective degree.... Examples of an easily modified design are the 13XX and 22XX/Disco valves, whereas the MRod and B51 valves don't have much room to round that corner or hog out the vertical port without relocating it (making a new valve and/or receiver)....

Bob

[Mike71]

Anyone make a replacement seal for the valve stem ?
Got a brass 13xx valve and would like to keep the stem (poppet valve) but definitely needs a new seal, got all of the old one out, got a white plastic bushing of the same type as the check valve but would need alot of work to get the size right. Or would the one in a new valve work in it ?

[rsterne]

Pretty sure that the poppet from an MRod fits the 13XX valve.... It is a 1/8" stem with Delrin head and seat....

Bob

[Mike71]

M-Rod.. that the discovery  ?

[rsterne]

No, the Benjamin Marauder rifle... The Discovery poppet has a 5/32" stem.... The PRod (Marauder pistol) may have the same 1/8" stem as the MROd rifle, but I'm not sure.... You may have the shorten the stem a bit, just grind it (slowly, with cooling by dipping in water frequently) to the same length as your existing stem....

Bob

[rkr]

rkr, I am not familiar with the Evanix, but if the porting is less than 80% of calibre, then any improvement in the porting can cause huge improvements in flow.... As the porting approaches bore size, such changes may not make as much difference.... Just my experience, YMMV of course.... Rounding any turns on the inside corner does, indeed, improve the flow.... Unfortunately, in some valves, the exhaust port is so close to the inside rear of the valve (where the seat is), you cannot do that to any effective degree.... Examples of an easily modified design are the 13XX and 22XX/Disco valves, whereas the MRod and B51 valves don't have much room to round that corner or hog out the vertical port without relocating it (making a new valve and/or receiver)....

Bob

In this case the port size was not changed, just the sharp 90 degrees turn was made smooth with decent radius and that made the speed jump up. I did later go for big ports but that's then another story. What you described Bob will also work but often there's not enough room for that so taking the sharp edge away from that 90 deg turn is definately worth it.

[rsterne]

Just curious.... How big was the valve throat and the exhaust port diameter.... just roughly?....

Bob

[Mike71]

No, the Benjamin Marauder rifle... The Discovery poppet has a 5/32" stem.... The PRod (Marauder pistol) may have the same 1/8" stem as the MROd rifle, but I'm not sure.... You may have the shorten the stem a bit, just grind it (slowly, with cooling by dipping in water frequently) to the same length as your existing stem....

Bob

AHH thanks, was reading alot and came across prod, mrod and remembered it was for one of the pistol/rifles, does it need to be the white or black plastic ? If I remember the black is harder and for higher pressure.
And that valve in the pics is awesome.

[rsterne]

I have never found any difference between the black and white Delrin, but there are some poppets that are white that are indeed a softer material, maybe Teflon?.... The Molded over poppet in the Disco (which is quite large in OD) is formed over a "T-shaped" stem, and is softer than the MRod poppet.... The black MRod poppets are good for about 3600 psi on a stock throat size without deforming, the larger you make the throat and valve seat, the less pressure they will stand without deforming.... Having said that, the black MRod poppet will work on a 0.266" seat at 3000 psi, so they are pretty tough.... That is my preferred poppet if I am not making my own out of PEEK.... The harder the material, the more difficulty in sealing it....

Bob