4.3 lifter torque

i have just replaced a blown head gasket cleaned and re-installed original lifters and pushrods in the same position as well as the rockers, torqued them to 18 ft.# went to start had no compression , loosen rockers turned over motor now have compression . what was wrong did i use the proper torque setting is there a sequence for tightening? 2000 olds bravada 4.3l vin ''W'' roller cam and rockers w/ positive stop shoulder bolts.

Try tighting them slow or a little at a time.