What is this, what does it do and why is it there? It sits right above the oil filter inside the oil pan. Its off a 08 LY6.

 

your not kidding calling it a relief, sure looks like it!
I wouldnt think it'd be for the oil filter cause that has its own relief, but maybe its for the lines, in the event the cooler gets clogged or the line gets pinched maybe

whats above it in the block?

 

Yup pressure relief valve.

GM LS-Series Engine Oil Pan Dimensions

 

Theres nothing above it just regular engine internals. Can it be removed and plugged? The older oil pans didnt have this.

 

Yes.

 

That valve vents pressure for the AFM lifters.

 

Yup blows off at ~55 psi.

Note it’s also included in some non-AFM combinations, likely owing to hardware deproliferation edicts.

But who here hasn’t deactivated cylinder deactivation? :D

 

Splinter and Preston have pretty well answer your question but I thought it may be worth mentioning that valve has been known to spray so much oil on the cylinder 7 walls it can actually gunk up the piston rings and drop compression. GM has a bulletin and even pruduced a sheet metal hood that fits over it and helps direct the spray away from the cyl walls. Just another reason to hate AFM.

 

Lol I just found that bulletin on the Alldata at the shop yesterday. The G8 GT I have also has this crap and as soon as I can do a dod delete ill cap that relief valve on it as well. Thanks guys.

 

Now on another note, does anybody know what thread pitch is on this thing. It looks almost like a AN fitting and none of the regular parts store fittings ive found seem to match.