bottom pulley
note the tiny pin-hole on the bottom crankshaft / alternator pulley,
I find just undoing the 3 x M8 ( 13mm /Hex) bolts is enough to lose the fan belts tension.., getting this little hole aligned with the "pip" on the crank pulley is crucial for ignition timing, as there is a pulse point on the outer pulley.. for the crank angle sensor.