[colton]

i finished rebuilding a lombardini engine last night (single cyl diesel, air cooled), the torque sequence for the headbolts was;
stage 1: 30Nm
stage 2: minus 180 degree (at which point the bolts were less than hand tight)
stage 3: 20Nm
stage 4: plus 72 degrees.

come someone tell me why for each of the stages, i wonderstand why you would go in stages but why minus 180 degree's?
also why turn 72 degree's and not torque to say, 60Nm for example?

i did a transporter engine and it had similar style sequence (though much bigger torque settings!)

 

[8valve]

to pre-stretch the bolts maybe?

ps - I may be talking thru me hole!

 

[TrevD]

maybe to pre squeeze the gasket

so to get a true torque reading on stages 3 and 4

ps like 8 valve i may be talking through me hole