I agree a 100% with Gene on the anti seize. Not only does it help against galling, it also helps to protect against galvanic reaction and electrolysis. And those split lock washers? They don't work very well in my testing at work. If you have trouble with screws backing out, I would suggest to never put loctite on the threads of an engine. But if you still have screws coming loose, use the anti seize on the threads, and apply a small amount of the permanent type of thread locker like Loctite 290 under the head of the screw and on the mating surface. You can do that after the screw is tightened, it will get in there and you will still be able to remove the screws.

At work we use Loctite 290 to hold the outer race of bearings with only 0.0002" clearance.