Procedure for adjusting the PS valve is in the shop manuals. Bear in mind that this problem might also be wear or dirt in the valve, rather than simply adjustment
You can download some:
70-71 Mopar Parts
[ame="http://www.abodyjoe.com/pictures/Misc.%20car%20info/1970-71MoparParts.pdf"]http://www.abodyjoe.com/pictures/Misc.%20car%20info/1970-71MoparParts.pdf[/ame]
72 Service Manual
[ame]http://www.abodyjoe.com/pictures/Misc.%20car%20info/1972%20Plymouth%20Chassis%20Serv%20Man.pdf[/ame]
69 Dodge Serv. Manual
[ame]http://www.abodyjoe.com/pictures/Misc.%20car%20info/69%20dodge%20service%20manual.pdf[/ame]
70 Dart Challenger manual
[ame]http://www.abodyjoe.com/pictures/Misc.%20car%20info/70%20Dart%20Challenger%20Serv%20Man1.pdf[/ame]
71 Dodge Body Manual
[ame]http://www.abodyjoe.com/pictures/Misc.%20car%20info/71DodgeBodyManual.pdf[/ame]
65 Plymouth Manual
[ame]https://www.dropbox.com/s/upks33txhbe9tjw/1965%20Plymouth%20Service%20Manual.pdf[/ame]
From MyMopar:
http://www.mymopar.com/index.php?pid=109
In the 69 manual, page 19-7. Now, the first sentence is the last of reconditioning and reinstalling the valve, so in your case instead of "tightening to 7 ft pounds" It should read something like "loosen screws and retighten to 7 ft pounds." This is so the valve will slide when you tap it, but won't leak