Cracked Valve Guide Pillars - OK to Use?

That one where you have the spring off has had the guide replaced. When that was done, the shop should have milled the rest of the factory guide off, but they did not. If all you have is the factory guide like in that last picture, you can dress the top of the guide with a file to make sure there are no sharp edges on it. That will help it from not cracking or breaking any further. If they are cracked really bad though, like all the way to the spring seat for instance, the guide(s) should be replaced and the old guides milled down to the spring seat. Then you can run the valve seals that press right onto the ends of the guides.