My 97 Defender has a tiny weep at the rear of the head. The engine was rebuilt about 95000 km ago - I have been advised to tighten [retighten?] the head bolts by first 'cracking' one loose then torquing it up and using the same procedure on the rest. Since the bolts will not be removed, should I use a torque value - or should I simply go with a degree value? [e.g. 15 or 30 degrees more than where each bolt was]