Bill, why would you take off the muffler to rotate the crankshaft ? Remember - there's a transmission and some wheels mounted to the motor, too ! Simply move the car an leave the muffler where it belongs. To make it easier you can take out the spark plugs and replace them while there. just my 2 cents.... Elvis 4) Have never adjusted PRV valves (actually tappets that push on them), but don't look any different from other adjustable valve trains. Time consumed isn't going to be actual adjusting -- is going to be digging down to valve covers, then putting everything back. You'll also lose time removing/replacing muffler to access big nut on crankshaft to turn engine. See now why I recommend doing your own mechanic work? Bill Robertson #5939