I was wondering what the diameter was of the exhaust port on a Dr Bobs valve. My current factory port is 4.6mm and I'm trying to squeeze a bit more power of my .25 mk2. I was planning on doing this and the high flow SS valve as well. Thanks
if yours is original it should be 4.7mm port as thats the smallest you can go as the shank part of the stem is 4.7mm and this as to pass through.you need 5.5mm if its unreged also barrel port at 5mm.theoben normally did 4mm,a valve chamber extension would also help.
KevG
Thank you very much, this info is much appreciated. Would one of Bobs valve body/stems help get a bit more air to the barrel port? I've opened it up (the barrel port) to around 4.8mm and saw around 25 fps increase, but was hesitant about going much more. Original size was 4mm as you said.
Get Kev to sort it for you ⬆️
I have a Mk1. 22 FAC #000092
I bought a stainless steel valve on Ebay to replace the the black plastic one.
Would this cause any problems?
TIA . JOHN
Quote from: SETANTA on March 24, 2026, 04:42:49 PMI have a Mk1. 22 FAC #000092
I bought a stainless steel valve on Ebay to replace the the black plastic one.
Would this cause any problems?
TIA . JOHN
Probably, as the only seller I can see, is one I avoid like the plague because anything I bought off him/her/it has been crap.
Theoben replaced the stainless with the black plastic as an upgrade, buy the valve & stem as a matched pair from either Kev or DrBob.
Basically it's a copy of the short body RAW power valve.
I know of a few people that have purchased one -'just to see' and apparently it works but not on par with a custom valve made for the application - KevG, Nick Cook, Bucketboy.
I'll agree with Angrybear in saying that PCP-GP products are very hit and miss, mostly miss.
Over time people have had recurring issues setting up his standard valves and his -'genuine' regulators are junk.
Thanks for the reply and advice, much appreciated.
All the very best.
John
Hmmm stainless steel valve I'm pretty sure i have one of these in my spares box you could have had it if you hadn`t bought one already.
I`m pretty sure i have one of them not 100% but I'm pretty sure i do have one.
Yep I think I've got an old Theoben one somewhere,
I've also got a reverse valve with the spring on the hammer side ??? but I've never tried it.
Amazing what we pick up over the years. 8)
Quote from: angrybear on March 25, 2026, 11:55:55 PMYep I think I've got an old Theoben one somewhere,
I've also got a reverse valve with the spring on the hammer side ??? but I've never tried it.
Amazing what we pick up over the years. 8)
are these reverse valves any good? I like the theory of getting a bit more air volume
Quote from: JoeB on June 11, 2026, 05:10:17 PMare these reverse valves any good? I like the theory of getting a bit more air volume
Can't tell you as I've never fitted it.
They help using air,
12ft/fac,
Dad's lever block running plum on 30ft on 16g ammo. 16in barrel.
So a 21in barrel be running around 1000fps,