tecchris, i think you're on the right track. it looks like you have the wrong piston size.there's no way you would have 74# suction and be low on gas with a return air of 73 deg. the piston is too large, not allowing liquid to back up into condenser for subcooling.install a t.x.v. and charge by subcooling (6-8 deg.) then set your superheat.but, make sure the t.x.v. is not commercial,must be for residential with off cycle bleed port.or,find out the correct piston for the cond. unit.
Alot of residentcial txv's are non bleed.
Next why only bribg the sub cool to 6 or 8°, and then adjust superheat?
Where talking a/c not walk in freezer.
beenthere,6-8 deg. is my starting point,then set s.h.,then depending on seer (forgot to mention), i would add refrig. for 8-13 deg sub. because if it's only 85 deg. outdoor amb. i would worry about higher than normal head (causing higher amperage draw, killing eff.) when it got to 95 deg. amb. just my way of doing a piston to txv upgrade. thanks for the tip on resdential txv's not all having % of bleedport. i shouldn't rely too much on supplier info.
i will be willing to bet this is an old fedders with cap tubes. the head seems a little low and super heat a little high should be between 12 and 15 degree superheat. your head may wind up arround 250. if my memmorie is correct about those old war dogs.