705mm give or take 5mm. I have a billet alloy harmonic balancer on mine that I made up to make it shorter to clear my thermo's, it is 690mm from the back parting face of the block where the box bolts on to the front of the bolt that holds the harmonic balancer on, and I only took the 3PK belt off the front of my pulley, so I'd guess pretty accurately that its close to 705mm. I think there is a bit on the back of the cylinder head that sticks out too where the heater hoses go on, its about 20 or 30mm so I'd allow 740mm to drop it on. You can do waht I did though, if you don't run a heater/demister in the car, just put a plate over the hole at the back of the head and drill and tap a 1/8bsp hole in the side next to it and run the hose back to the water pump from there. This will give you 705mm.