I'm trying to free a valve stem that's stuck on the valve, also two slide ends (as in the dump slide of the third valve slides) that are severely stuck. I've had the parts soaking in a glass of PB Blaster, for six days now. I try to remove the parts every day, by twisting the valve stem and using a shoelace on the slides. They won't budge... what should I try next? (Or should I continue with the PB Blaster? Could it cause any damage over long periods of time?) I may end up bringing these parts to a tech... what methods would they use to free the parts?