Keep the same concentration of salt. Just increase the volume. I'd allow 2-3 hours for the loin.
I brine my Thanksgiving turkey overnight. I put it in the brine around 11:00PM then roast it the following day. You need a lot less time for smaller meats.
I think Alton Brown recommends 6-8 hours for a turkey. Overnight as I do it is probably near the upper limit. Pork loins and chops need a lot less. Certainly not overnight.
"If you want to make an apple pie from scratch, you must first create the universe." -Carl Sagan