its kinda hard to get 70-90 ft-lbs of torque on it, most of the time I just use the impact. Last time I actually tried with a torque wrench it was something silly like 35-40lbs before we couldn't hold the crank still anymore.
If the engine is in the car I usually stick a screwdriver or something through one of the holes in the damper and catch the oil pan rail to keep the crank from turning or if you have a manual trans and good parking brakes put the car in higher gear with the brake on.
Not sure if it is a good idea or not but it works. I pull one of the spark plugs and stick a long socket extension in there to keep the crank from turning ...
I tightened the fan belt really tight, and told my wife to hold the fan steady, while I cranked on it... Not really. Impact wrench will run it up tight without trying to turn the motor too much. Also nice to jam something in there, just in case, and to keep it from moving in case you are trying to do some timing afterwards.
