The 4-way (input, 2 outputs, and exhaust makes 4) is screwed into the lower right side of the front block to the right of the regulator. It is coupled to the trigger by the timing rod which runs down the right side of the grip frame, bends 90 degrees, and goes through oval holes in the frame and trigger. The 4-way receives gas from the regulator into it's middle nipple, and sends the gas out to the front and back of the ram from, respectively, the back and front nipples. By operating the ram, the 4-way directs cocking of the 'gun.
Many replacement 4-way valves offer shorter switch-lengths (a shorter piston movement required to switch the valve from one output to the other. Most of these companies claim that this allows you to time a shorter trigger pull. I don't agree. Trigger-pull length is limited more by the sear-lug relation than by the 4-way.
- Original Stock 4-way Valve
Older stock 4-ways were pretty rough. The result of this was that it took a pretty stiff trigger-return spring to get the 4-way to cycle completely, limiting how soft you can make the pull when doing a trigger job. The result was many shops polishing the valve out for smoother action, allowing the use of softer springs. An unfortunate side effect was that if an inexperienced airsmith did it wrong, the valve would leak - a lot. Also, if the o-rings in the valve swell from absorbing CO2, the valve is extremely difficult (or impossible) to reassemble without replacing the rings. Budd Orr got the hint. The valves coming stock on the 'gun these days are much smoother than they ever were, and the promise of polished valves on the '97 'cocker should make things even better. I'll admit that I like to polish the current stock valves a bit to clean up the action a bit more, but most people don't want their trigger as soft as I like mine. The stock valve now is very good, very reliable, and I highly recommend keeping it.
- New Stock 4-way/STO 4-way/Belsales "Angry" 4-way
A while back, Keith Belsale had apparently tired of polishing and matching parts from stock 4-way valves because he designed and built his own aftermarket 4-way for his Evolution Autococker, and callied it the "Angry", presumably because of the emotion it was expected to elicit from Budd Orr. It was a brass, one-piece design with a shorter switch length than the stock valve. Since then, WGP has recognized the excellence of this design and has included it as stock equipment on STOs since 1999, and stock Autocockers starting with the year 2000 model. It is now aluminum and comes with a properly fitted piston (a problem with earlier models was finding a piston that fit properly).
- ANS 4-way
ANS has their own aluminum 4-way valve. Much like the Angry and Nemco valve, it is a one-piece design with a short throw. These have become quite popular of late. Some of them (particularly those already installed on ANS custom Autocockers) work extremely well. I have, though, heard many reports from people who purchased them as aftermarket add-ons for their own 'guns and suffered many leaking problems. As such, I'd say that if you are buying a 'gun with one already installed, you're probably safe. Most shops will test a 'gun before shipping. If you're planning on buying a new aftermarket 4-way for your own 'gun, though, you may wish to look elsewhere.
- J&J Stainless Steel 4-way
J&J was selling a stainless steel valve that was extremely smooth. Unfortunately it also suffered chronic leaks due to improperly sized o-rings. Rumor had it that those problems were ultimately solved, but I never saw one that didn't have problems. I haven't seen one of these on sale in this area in a long time now. If you can find one that doesn't leak, they are damn smooth and may be worth your money. On the other hand, the stock valve can be made just as smooth for much less money.
- KAPP 4-way
KAPP´s 3-way is an aluminum one-piece, short-throw valve not unlike the Angry and hoards of other aftermarket valves on the market. KAPP sent me five valves in five different colors and all were identically smooth and leak-free. That´s one nice thing there. Aftermarket 3-ways are notorious for leaking. I have found KAPP´s valves not to leak at all. As with most aftermarket valves, it has a short switch-length.
KAPP´s valve has a couple of nice extra features. First, like most KAPP aluminum products, they are available in chrome and a variety of colors. Second, a small screw in the front end of the valve acts as a nice extra safety feature to keep the piston from shooting out the end if it ever comes loose (I know it never happens, but that´s why it´s there). The cool thing is that KAPP will soon be offering a feature that allows you to replace that screw with a small nipple and hose to route the vented gas up to your feeder elbow, giving you a gas-assist feed not unlike what Smart Parts offers on some Shockers.
- Nemco Aluminum 4-way
I don't know if Nemco is even around anymore, but this has some historical relevance at least. Nemco used to distribute a very short aluminum 4-way without end-plugs. The claim was that this valve will make for a shorter trigger pull. I've had the opportunity to tinker with a couple of these. The stroke is marginally shorter than the stock valve, but not enough that I think it's worth the money. Additionally, when it comes to actual trigger-pull length, I've found that it is harder to get this valve timed in correctly with an extremely short pull than it is with the stock valve. If you don't want to do any other work and looking for a quick trigger-shortening, this valve might be worth having. On the other hand, if you're looking for an extreme trigger-job, I think that the stock valve is easier to work with.
- Palmer Quickswitch
Much like many other companies out there, Palmer's tired of wrestling with the quality control problems that have cropped up in stock 4-way valves of late. In response, Palmer took his 4-way design from the Blazer (his production Autococking paintgun) and put it into a shell that could be mounted on the Autococker. It looks almost identical to the stock valve from the outside, but when you take it apart, you find quite a few more parts inside. The advantage of the Palmer 4-way is a shorter switch length and more even wear on the piston o-rings. Where most of the short-throw 4-ways run the piston o-rings back and forth over drilled holes, the Palmer valve does not, leading to a claimed improvement in o-ring life and valve reliability.
For a while, this was my favorite 4-way valve. When you get a good one, it is simply awesome. The problem is that he seems to have sacrificed some of the superb reliability for smoother action. As a result a lot have been coming from the factory leaking unless you turn the pressure way up. Very irritating. Some work perfectly, though, so if you get a good one you're in good shape.
- Shocktech "The Bomb" 4-way
This is my new favorite 4-way valve. Danny Love has put together a completely new valve here that works very differently from every other 4-way on the market. It works so differently that the hoses are actually reversed, the front hose going to the front of the ram and the back one to the back of the ram. This new design has a three O-ring piston, the three standard hose-barbs, and and two rings of holes used as vents. I may put together some diagrams to show how the valve works sometime, but for now, take it from me, it works. This is not just a good valve, it is the best 4-way on the market for the Autococker. The new design allows for the shortest switch-length in the business (yes, shorter than the QuickSwitch). The longer piston and three O-rings make it much more stable and unlikely to be twisted to the side far enough to start leaking. Finally, it is exceptionally smooth - not as smooth as the new leak-prone Palmers, but I'll gladly trade that for the Shocktech's leak-free performance, reliability, and ultra-short switch length. Absolutely the best 4-way now available.
There are other 4-ways out there; mostly plated or anodized versions of the above mentioned valves. The hazards are the same as found with plated rams - poorly done work will result in a sub-standard valve.