Rover sd1 v8 timing

[cerbielee]

Hi all, when doing the timing on my car the pulley markings show its 180 degrees out with my strobe light! but the engine runs sweet! im using plug no 1 lead, is this correct? when i altered it so timing marks lined up it didnt run??? am i doing it right or is there a different way of doing it?
Thanks for any advice fellas!