PCV question
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Joined: Nov 2005
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PCV question On a 2015 L83--5.3, I have no DOD/AFM, the valley towers are plugged, it's turned off in the tune. Do I still need to have a hose run from the front of the stock valley plate to {somewhere)? I have the fitting blocked, but it shows to have some oil mist around that area. I have a Motion can with a breather hooked up to both valve covers.
I checked it because I am moving the engine to another car. I pulled a couple of plugs so I wouldn't break them off and they were oily and black---this is a new rebuild with forged parts--yep, I did it. Maybe that's the problem. I saw an article from GM about these 14-16 5.3's using oil and one cause was the PCV. Another was the low tension oil pack. I used the new rings from Diamond on this. So, that's my question---Do I have it plumbed wrong by blocking the front port. Seems like the catch can and breather should suffice?
I have stock exhaust manifolds. I checked the exhaust pipes just coming out of the manifolds and they are black but dry--no oil. Strange. I hate to pull the blower and heads off this thing and find out it is the valley hose. Any help-----Thanks!
I checked it because I am moving the engine to another car. I pulled a couple of plugs so I wouldn't break them off and they were oily and black---this is a new rebuild with forged parts--yep, I did it. Maybe that's the problem. I saw an article from GM about these 14-16 5.3's using oil and one cause was the PCV. Another was the low tension oil pack. I used the new rings from Diamond on this. So, that's my question---Do I have it plumbed wrong by blocking the front port. Seems like the catch can and breather should suffice?
I have stock exhaust manifolds. I checked the exhaust pipes just coming out of the manifolds and they are black but dry--no oil. Strange. I hate to pull the blower and heads off this thing and find out it is the valley hose. Any help-----Thanks!
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Joined: Jul 2025
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From: United States
Yes, you need that front port connected. Even with AFM/DOD deleted, that front port on the valley plate is a primary PCV source for crankcase vapor. Blocking it forces pressure to find another way out, often pushing oil mist past seals and causing the oily plugs you're seeing. Run a hose from that front port to your catch can intake side. Your current setup is likely causing excessive crankcase pressure.
