Thanks for the advice. I thought these heads were a bolt on and go? It sounds like alot of swapping parts that are already assembled on the head. I don't like the idea of swapping the locks, retainers and springs to fit in an XE274 cam which isn't much bigger than the stock one, it seems for $1000 these heads should be able to support that right out of the box. So far the vibe I get is these heads are junk.