Many times the valve cover hangs on the aftermarket runners. Some covers are clearanced on those spots, some are not. Cast covers on SB's are notorious for not sealing as the hang up on these runners. After a little grinding, they sit flush. Use 2 cork gaskets cemented together and you dont have to clearance. Worth checking. 40 inch/lbs or 3.33 ft/lbs is snug at best. Use a nut driver. Can get a way with a little more with a cast cover that doesnt deform.