I bought an older 10 lb NOS bottle that has a high flow valve, but I want to swap my super high flow valve from my 15 lb bottle as I'll be using the 10 lb bottle as my primary bottle. I put a wrench on the top of the valve and I can't get that sucker to budge. Any tips on how to get the valve off of the bottle?

 

just keep tryin, maybe try a strap wrench on the bottle to hold it...it'll come out eventually

 

Hold bottle firmly and strike the attached crescent wrench (counter clockwise) with rubber mallet or dead blow hammer to loosen. You can lay the bottle flat on its side against carpeted floor while sitting on top of bottle to hold.