could someone please identify this please

I'll take a stab and say it's a PCV valve. Positive Crankcase Ventilation. Uses manifold vacume to pull air out of crankcase. Usually in the back of the intake on most GM.

Beautiful work on your engine.  Valve covers are da bomb! Keep us up on your build.  Ya know we like pic's.

2 hours ago, JUSTA6 said:

I'll take a stab and say it's a PCV valve. Positive Crankcase Ventilation. Uses manifold vacume to pull air out of crankcase. Usually in the back of the intake on most GM.

justA... this gets me every time i see a pcv installation... if you run with open venting valve covers, does that justA cause one big vacuum leak ? you have a vacuum draw pulling from the manifold clean through the motor and in from the valve cover.

i would expect the valve covers to have sealed oil filler caps on them along with the dip stick too  ? isnt that how its suposed to work ?

The PCV has a one way valve in it and is not always open.  Intake vacume pressure drops with RPM.  If pressure exceeds the limit, it sucks the oil/fuel mixture back into the intake to be run through the heads again. Even with breathers in the valve covers, you only have 1 return oil passage in each end of the head and you have oil flowing through that to boot leaving a small vacume leak as you said.  But blowby from the rings/cyl can far exceed that, turning your block into a backup cylinder.  Usually this is only a major problem in race cars, but becomes an issue with higher mileage cars with well worn rings.  Stop the grenade effect of the engine, as we have all seen in racing.  One thing to have an engine fire in a fire suit, quite another to get yourself and passengers out of a burning car.  Or at least that's the way I understand it.😟

Simple explanation also is pcv system replaced a draft tube. Cylinder blow by pressurizes the crank case. This needs vented. Tree huggers wanted those emissions captured instead of releasing them to the atmosphere. So they took the draft tube, in a manor of speaking, connected it to the intake manifold through a valve. In doing that you create negative pressure & in time would suck all the oil that became vapor out of the crank case. So they needed to equalize the pressure to zero or as close as possible. The fresh air supply originally came from the air cleaner to the valve cover & down to the crank case. Most hot rodders disconnected that connection & put in breathers. Sometimes in one sometimes in both.
The main problem this caused was engine sludge & carbon buildup on various parts. These problems precipitated major changes in engine oil chemistry.