[8695Beaters]

I can answer this one: wear. Sloppy valve jobs tend to show up later on. It may be fine when you start out (especially with brand new parts), but as stuff wears out, things turn ugly quick. I assume you beat on your car pretty hard, which only accelerates the problem.

If I were you, I'd find a junkyard motor. Swap it in and get your current motor completely looked at. Upgrade whatever you want or whatever needs to be replaced. Then drop it in. Having the junker will give you a car while you're figuring out what's wrong with your good engine. Plus you have a backup if something else goes wrong. If you have a backup car, then you can skip this, but bottom line, it sounds like you're going to have to invest some time and money in this one.