cyl head bolts are stretch bolts, so use new ones!
stage1, 18lbft (25Nm)
stg2, tighten further 85 degrees
stg3, tighten further 85 degrees
stg4, tighten further 20 degrees

tightening sequence:

i n l e t s i d e

10 6 2 3 7

9 5 1 4 8

e x h a u s t s i d e


loosening sequence is reverse of the tightening sequence.