Hi,
Unless the PA22-150 maintenance manual specifically addresses that application, (I don’t have that manual) the go-to source for aircraft bolt torques is the table in Advisory Circular 43.13.-1B, the mechanic’s bible. The title of AC 43.13.-1B is “Aircraft Inspection, Repair and Alterations.”
The torques in the table are for oil free cadmium plated threads.
The table gives a torque range (in inch pounds) for bolts primarily loaded in shear and for maximum allowable tightening torque limits. The torque in a shear application for the AN6 bolt while using a MS20365 or AN 310 nut is 160 to 190 inch pounds (13.3 to 15.8 foot pounds) with a maximum torque of 390 inch pounds (32.5 foot pounds).
This doesn’t quite do it because these bolts are primarily loaded in tension–the load is trying to pull the mount off the airframe.
I did further checking in the Piper PA 28 service manual (140 up through 235) and the torque specified in that manual for the AN 6 bolt and MS203655 nut in the mount to airframe application is 230 to 240 inch pounds. You’ll be OK using the 230-240 value for those bolts.
