hello Fiachra, just done a n46 which looks similar, i would expect at the very least you would need to drop the sump and let it rest on the subframe as it bolts to the timing cover if its like the n46, mine had jumped at least 25 degrees and done no damage to the valves. my problem was finding the locating hole for the pin to lock off the flywheel which was supposed to be near the starter, i removed the manifold and starter in case i was being a div. in the end i used a screwdriver to set number 1 cylinder to TDC. engine started and ran first time.anyway good luck
chris