if its anything like the 2.5 pulley, then its quite easy
just put 2 longish m8 bolts through the pulley where the second ring bolts on, and just keep winding each one gently to bottom out the bolts onto the,
ahh i wuold have said bottom cam belt pulley but as yours is chain drive i'm not sure never stipped a 2.8
mmm
not sure then, sorry