MGB: Crankshaft Pulley Bolt

I have gone through the threads on removing the crankshaft pulley and chankshaft bolt. My problem is that my bolt actually backed itself off since someone forgot to either torque it to the 70 ft. lbs. and did not bother to pull the washer tab over the bolt. I am about to take the vehicle off of the jack stands after working on it for the past two years and was just looking things over in general when I found the bolt backing out. Since the vehicle is up in the air, I applied the handbrake, put the vehicle in gear, and when I go to tighten up the bolt, all I get is the pulley turning. I have tryed a wedge of wood between the pulley and the sub frame with no success. Any one out there with some tricks on how to get this thing torqued up?
As always, thanks in advance for any and all comments.

heard something about rope inside number 1 cylinder. guess it dosen't matter which cylinder.. remove your spark plugs and see which one is getting closest to the top. stick a bunch of rope in there, (some hanging out the plug hole obviously) and try to crank it with your wrench. should stop engine from turning and so u can get the nut off.

By "all I get is the pulley turning" ... do you mean the pulley & engine are turning OR do you mean the pulley is turning on the crankshaft?
If the pulley is turning on the crankshaft, you've lost your key.
You might want to consider renewing your oil seal on the timing cover if it has been buggerd up by your efforts with the crankshaft bolt.

I have always just put them on with an impact wrench!! Tight!!!

David, when I turn the bolt with the car in gear, you can see the drive shaft turning. The engine runs like a top. When I apply rear brakes, I know longer see the driveshaft turning but the pulley and bolt move in unison as I turn the bolt clockwise. Does the clutch have enough grab to hold the whole works while trying to tighten the bolt? And Gary, I don' t have an impact....maybe in another life time??? But thanks for the suggestion anyways. Evan, I have used a rope inside of a aircraft engine before to take down a stuck valve. Makes sense that it would work in the cylinder to stop the engine from turning. Just wondering if there is another way besides the rope trick?

I mentioned using the rope trick on my Midget and it worked successfully to tighten the pulley bolt. There is no way to get a socket on the bolt on a Midget so an impact was not an option. The Midget also has a big inspection plug up on top of the tranny bell housing so an option would have been to jam a pry bar into the ring gear to stop the engine turning. There is no place you could do this on a B except maybe where the clutch arm comes through the side of the tranny.
If the bolt and pulley are turning but not the crankshaft of the engine then I agree with the comment above that your key has fallen out of the keyway. If the pully turns the crank has to turn if the key is in place.

Something's fishy. I recommend that you completely remove the bolt and pulley and check to see if you actually have a key in there. If the pulley is turning & the crankshaft isn't, = no key.

Tom L said:
"David, when I turn the bolt with the car in gear, you can see the drive shaft turning. The engine runs like a top. When I apply rear brakes, I know longer see the driveshaft turning but the pulley and bolt move in unison as I turn the bolt clockwise."