Locks can cost you an engine, no joke. I buy good locks and retainers. Hell, springs too. I dropped a valve once, my stupidity for not keeping a better eye on things. When I measured the spring pressure they were all down 40 pounds from new. But, some of that was simply from the titanium retainers getting eaten-away. They were so damn thin, almost razor blade thin, I couldn't believe it! When I checked the springs they were actually only 20 light, the rest was gone from the spring seat and retainer. Well, over-rev the thing and caught an intake. I think that was a $5k bill to fix it all.
Brandywine Cylinder Heads in PA, they did an incredible job making those heads look brand new. They will always be my go-to place for a major repair. Wish I could find the pictures. They say they can even rebuild a missing combustion chamber.............
Fox, buy good locks, seriously, do not use that stuff! If you do not know if their retainers are good stuff, look at titanium from a good supplier. Yeah, they run about $300 now. You really don't need titanium, tool steel will be fine also. You can not take chances on those parts.