Advice please....clyinder head torque settings rover 420 gsi

stage 1 = 45Nm stage 2 = 80Nm stage 3 = a further 90deg , using an angular torque gauge

in this sequence with oil film on bolts threads and underside of bolt heads

8 6 2 4 10

does the turbo head reduce the compression ?

Thanks , I tried to get a manual but all that was in stock was from M plates onwards. I don't think it is going to reduce compression (hopefully) but have hit a slight snag, the guy we got the cyliner head from did not have the rocker covers and the non turbo ones are different, no luck in getting them as yet.