It's hard to explain, but I can make the inlet cam turn once, and it snaps into position, with the lobes forcing one pair of valves down, but then as soon as I go to turn it again it won't turn at all, which is strange because the next immediate part of the turn is releasing the lobe off the valves, and should turn easily before it starts forcing down the next pair of valves. I would have thought that if valves had bent then it would stop turning as it starts forcing down the next set of valves. Hope this makes sense.