Re: Engine knocking at startup
I think you're confusing some things here so we need to figure out what the real problem is first.
The PCV Valve is part of the crank case ventilation system. It isn't going to have anything to do with noises coming from the engine. No harm in replacing it. But also no surprise that nothing changed. Kind of like changing your brake pads and expecting oil to stop leaking.
KNOCKING is a sound generated when the mixture in the cylinder ignites prematurely, burns too quickly, or burns unevenly. In simple terms, it goes bang when the piston is not in the proper place. This cause a knocking or pinging sound, reduces power, and in extreme cases, can wreck shit. Knocking is often caused a build up of carbon and other shit in the cylinders. It can also be caused by timing problems, spark plug problems, leaking fuel injectors, any any other random weird crap that fouls the inside of the cylinders. This really doesn't have anything to do with oil weight or PCV valves at all.
SEAFOAM is for cleaning carbon and other crap out of the crankcase, cylinders, valvetrain, fuel injectors, manifold, etc. Adding it to the fuel tank cleans the injectors. Adding it to the crankcase (oil) before an oil change kind of flushes and cleans it out. Adding it through the intake manifold or throttle body cleans out the valvetrain and cylinders. This can fix knocking if the problem is just built up carbon and crap.
CLICKING NOISES that may sound suspiciously live the valvetrain tapping away is exactly that. This is due to a lack of oil up at the valves. If the truck sits for a few days at a time, gravity will do its thing and the oil up there on the valvetrain will drain down. When you first fire it up, you might here some clacking until the oil is pumped back up there and coats everything again. Mine does this all the time because it sits for days at a time. It is not necessarily a problem as long as it goes away in say less than 30 seconds. If yours is doing this for a long time, it could be a few things. The oil pump could be on its way out and slow to pump the oil all the way up there. If you use too thick of an oil, it could be slow to reach the valves, but you're not doing that. So don't start. If the oil passages and valves are gummed up, it could cause this too. Seafoam in the crankcase and an oil change could fix this.