That was my thought as well, given that the pulley rotates and that it's located via key and the belts holding it straight I thought it unlikely it would go anywhere anyway. I'll get that bolt as tight as I can and call it good. I have a couple of jobs left to do anyway, I noticed I have a very slight oil leak from the oil cooler line that goes in above the oil filter so I will be removing that to double check everything and stop it leaking. Otherwise, I'm pleased with the rebuild, it went fairly smoothly and I learnt a lot about the engine during the process, I actually find the P38 design pretty good, despite all the bad press it gets I think it's an excellent vehicle, possibly let down a little by usage of poorer quality items here and there (such as the stupid exhaust manifold heat shields - why are they not made of stainless with rot proof fittings!) and crappy plastic on some of the connectors.