It's either a 4T or 7T grade M14 bolt, have a look on the head of the bolt and there should be a number, if it's a 4 the tightening torque is...
74Nm or 7.5kg-m or 54ft-lb
If it's a 7 the tightenig torque should be...
127Nm or 13.0kg-m or 94ft-lb
according to the factory service manual.
You'll have fun fitting a torque wrench down there:P