252 foot pound error

[Daniel Gervais <itpmtlplant@videotron.ca>]

Two weekends ago I completed some work on my 86 coupe ( chg timing belt
...) during wich I had to tighten the crankshaft 29 mm nut to 252 foot
pound torque, the way I did it was to extend my 1/2 inch torque bar with an
extension to give about two feet from wich I basically sat on (140
lbs*2=280 foot pound) !! .

I though that with 280 foot pound this would be sufficient. However I
re-read my bently and it says 252 foot pound with their extension tool 
2079. (wich I read somewhere on the net is 18 inches long) depending on the
length on your original torque wrench this could double the real applied
torque to the bolt, so my question is , what is the real final torque
applied to this bolt ??