If tiny charcoal particles are getting out of the canister, that’s not the particles’ fault, that’s the fault of the screen or filter that’s supposed to be keeping them in! I rebuilt mine as well, earlier cylindrical canister, and replaced the filter element with a coffee filter. Never had any particles get out again. I’d still recommend installing inline fuel filters in the lines, though.
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I’m not sure if the valves are reversed or not. What I did to my valve was wrong and led to fuel smells in my trunk.
Heres the definitive way to test which way is which.
Blow through both of the larger ends. One side will let you blow through after apply some
pressure. That is the side that attaches to the hose from the gas tank.
The other end will allow you to blow a tiny amount of air under heavy pressure, but significantly less than the other side. That end goes to the hose with the charcoal canister.
The 1/4 hose attaches to the small end.
Dont know how I botched it, but thought I would share.
I kinda remember the Rochester valve i bought had to be installed 180 degrees flipped from original design.
I really don’t think it makes any difference. It’s supposed to require a 2psi pressure differential to flow either direction, and applying vacuum to the third port is supposed to open it up so it flows freely in either direction. If it flows better one way than the other, I think it is faulty.
It does not. I bought a new one as well. The valve certainly opens up in both directions when the vacuum is applied, but without vacuum, it only works one way.
The replacement I bought is by Standard, the one on the car is AC Delco.
Then, I’m sorry, but I’d install two of them in parallel, one facing each direction. Excessive pressure in either direction will damage the fuel tank.
You can test it with mighty vac pump or blow into it to see flow direction… Some times it seems we beat a subject to death 
I did test it. I’m sharing the results.
The vacuum allows air to pass both ways.
No vacuum allows air to pass from the fuel tank after it reaches a certain psi force. It seems to leak pressure the other way.
There is no possibility of pressure from the charcoal canister, as the canister appears to always have an free open vent.
If the tank is in vacuum, the Rochester valve will slowly relieve it.