A loader valve should have one spool that floats, so you can float the bucket. Often that is used for back dragging to smooth dirt, or when scooping up material on a hard base that's not level.
A good loader valve is carefully balanced so you can raise/lower and curl at the same time. My old Kubota could do that and my current Branson can't. While it's not a deal breaker- I bought the Branson knowing how the valve worked- if I was going to the trouble to add a new valve I'd want it to let me do both operations at the same time. I don't know how you find that out though as its not in the usual specs.
I never did hear why the OP wants to change his original valve. BTW, his tractor is an open center hydraulic ciruit. Almost every compact and smaller tractor under 45 hp is open center. Many tractors up to 90 hp are as well. Most older tractors are open center with John Deere full size ag tractors and construction equipment being the notable exceptions.
If the tractor is closed center, it will have a pressurized container called an "accumulator". You can't miss it. Don't mess with it.
To replace valves, the port threads need to either match or use thread adapters. I like quick disconnects, but they are by no means necessary, just convenient. And more expense.
Multi-spool low flow control valve sets are inexpensive these days on the surplus mfg. goods market, I can't imagine why anyone would go to the hassle of re-plumbing with a used valve. But I'm curious. My bet is you'll eat up any savings just in hose & adapter costs.
No you cannot Tee off a open center pressure line. You can use the Power Beyond port to daisy chain blocks of control valves if you plumb them right, have the right PB sleeve installed in each valve, and run a separate return line from each valve block.
That ability to raise and curl at the same time is one of the things you get with a better quality valve - always assuming that the system has enough flow to do both at once. The other thing you get with a quality valve is greater precision at very low flows and small movements of the bucket and arms. With a really good valve you can move very,very slowly and repeatably in small increments. Taking maybe five or ten seconds for it to creep a quarter of an inch.
Float can be tested because the valve control lever will mechanically "stick" at the extreme throw. Doesn't need to be hooked up. Usually only one spool in a multi-spool valve body will have float. Float actuation is just a spring, a ball, and a detent in the spool. I don't use float much if ever. Some do.
good luck,
rScotty
