Stuck shower valve stem

I've stripped two valve stem wrenches trying to loosen the hot water valve in this shower. I've tried wd40 and heating it up with a torch to get it to loosen up but no luck so far. (I did get the cold stem to give after much grunting and some cursing)
The shower is one piece fiberglass and it backs up to another one piece fiberglass shower so I very much don't want to break anything loose inside the wall.
Are there any special techniques/tools to help with this situation? Some sort of special wrench or magic song to sing or something? I'm afraid to try another standard valve stem wrench because I'm afraid I'll start to round off the nut inside the wall and then never be able to get a grip on it.
Any shared experience would be greatly appreciated!
John
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Spray it again with liquid wrench several times over a couple of days. Remember that it is the threads around the outside and not the stem that needs to be sprayed. I have had better success with LW and time than with WD. A crazy as it sounds rapping it hard enough to vibrate it also helps.
Then use the correct size deep well socket instead of the cheaper valve stem wrench. Use common sense and don't kill it with torque.
Back to back sounds ugly. Good luck.
Colbyt
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John/Charleston wrote:

Use an automotive deep socket that's a tight fit. If the stem is too long to use the ratchet drive on the socket, put a pipe wrench over the outside of the socket.
The only limiting factor is how well the faucet casting is secured to the wall. If only the piping is supporting it, something may break...
Jim
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"> I've stripped two valve stem wrenches trying to loosen the hot water

Make sure you have the correct size stem wrench, and that it has a deep socket construction. A slightly oversized wrench will appear to strip, when it is actually a mite too large. Once you are assured the wrench fits right, tap the cross bar with a hammer to jar the stuck threads loose. As the other poster says, beware if stem is supported only by piping, as you may cause a pipe joint leak by overtorquing the stem nut.
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On Sat, 19 Mar 2005 22:31:14 -0500, John/Charleston

gosh John, sounds like that house you're working on is the money pit! Did ya ever get that oil tank emptied?
Bill
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wrote:

Melanie's Oil Services....they collect the recycled oil from auto stores etc. They got about 75 gallons out of my tank so I gather they got something for that but I gave them a bottle of wine anyway. Nice folks. Haven't filled it with sand yet though.
As for the shower valve, that's in a rental I own....
Thanks for all the responses, I'll get my a$$ to an auto parts store to find a 31/32 deep socket wrench and try to go easy.
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