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Just as the title suggests, I am wondering how the PCV system needs to be plumbed on an LS3 that does not have a valley cover nipple. Further, I have LS Holley tall valve covers, so each valve cover has a 3/8" nipple.
I thought I had it figured out until it started smoking like a freight train out the tail pipe and then found I had oil all inside the intake.
Currently, I have vacuum plumbed to driver side valve cover with a Beck Arney PCV valve and a sealed oil air separator. Fresh air is plumbed to the passenger side valve cover directly.
A buddy said I need something similar to the attached picture. He said the key was a catch can that can breathe so it doesn't force oil backwards through fresh air line.
Does anyone here know how it should be plumbed?
Last edited by bunkerbuster; Mar 19, 2018 at 07:24 PM.
Reason: Stupid phone
I think it should come from the drivers side valve cover through a sealed catch can and from the catch can into the intake manifold. The passenger valve cover should connect directly to the port on the throttle body or the bellow between the MAF and the TB.
I too was having oiling problems at one time on my build. It kept pooling up oil in the back of my intake and fouling the back cylinders and burning oil. I was told to put thread sealant on the rocker bolts but that wasn't it. I thought my initial sealed catch can setup was incorrect so I went with a breather can with 10AN lines off each valve cover thinking that was the problem but that wasn't it either. In the end I had pull my engine back apart and hone and ring all the cylinders again.
That is how mine is currently plumbed. This motor is a fresh build. We just pulled it out of the garage under it's own power. Chopped the throttle once or twice. Vacuum seems low at 8 in-Hg. It has a BTR stage 4 Cam, so it makes sense. I wonder if when we chopped the throttle it lost vacuum and put oil in the fresh air line. The picture attached is what did come out of the fresh air line. The other picture is how much oil is pooled up right now.
OP, basically you want the fresh air (low vacuum side) going into the port on the passenger valve cover and coming from a source BEFORE the throttle blade. You can choose to put a catch can here too as at long WOT runs it can pull oil back to the TB.
You want the dirty side (high vacuum) to go to the port on the driver's side valve cover (or would be the valley cover port if it was equipped) and connect to the intake manifold after the throttle body. This is where you want a catch can plumbed.
Now, the only thing I am unsure of, is on Gen IV valve covers there is a restrictor in that driver's side port that GM uses to function as a PCV valve. So adding another PCV in line would probably be redundant, but I don't think it would hurt anything.
BTW, search the forum for the "Is my catch can routing ok" thread, sift through 35 pages and you'll become a near expert on anything pcv related, lol.
I am going to try a catch can with a breather on fresh air side. I'll let y'all know how it works.
Also, I have the Holley LS tall valve covers, so no built in PCV valve.
I would run breathers for now and vent the crap to atmosphere just to see if your still getting oil in the intake manifold. If you do this and your still getting oil in there then you'll know for sure it's not pcv related and it's something else.
The oil is getting in and there's only so many ways it gets in. Past the valve guides on the heads, around the rocker arm bolts if the porting made it to the rocker arm bolt holes, the oil being sucked in via pcv system and last but not least the dreaded one of all past the rings! Good luck and keep us posted!
This is what I did for my build when I was getting oil in the intake manifold. Unfortunately for me this did not fix my issue as the oil was getting past the rings up into the runners and into the intake manifold. I'm still running the breather can.
these are the instructions for what you ordered. they come with the kit and are also hot-linked on the product page of the website. please read them and then let me know any questions regarding it you may have.
provided they are followed you will have a correctly functioning catch can system with integrated pcv control
Thanks for the replies. I'm going to try the catch can system, then see where I am at. I'm hoping it isn't rings. I don't see mist coming from oil neck, but we will see. I will say that I could see oil splatter clear past the MAF and into the SLP lid. (It's a 99 firebird with a LS3)
Ran it for 10 minutes tonight. Didn't notice any net gain in oil present inside the intake. Engine is burning off oil from last time. I'll just have to burn it off and run it on and off in the days to come and monitor closely.
I did get video showing some blowby. I capped off the vacuum and ran the PCV lines into a water bottle to see if I could collect anything. How does this amount of blowby make you feel? See video:
I seen the video and that's what you'd expect to see. It would be nice to see the rest of your set up in the car. Did you remove all the oil that was inside your intake manifold?
Just thinking that if they aren't baffled and you ran hose from those lines to the port on your intake manifold when the engine runs the intake would suck those oil vapors right in. You also had mentioned you had low vacuum. Capping off the intake manifold pcv port as you mentioned should get some more vacuum.
I'm by no means suggesting you not run a pcv system. To be emissions legal it's required but venting to atmosphere as a test to see if that's the issue I see no wrong doing. Another thing I noticed with my car was it wouldn't start smoking right away after start up but once the engine reached operating temp you would see some blue smoke. It seemed to be even more noticeable under deceleration then acceleration and like I said my rings on the back cylinders failed to seat.
I have manual tranny and when I got the car back together I went out on the road got it into 3rd gear and took it up to about 4g and took my foot out of it. I did this repeatedly and my car looked like a mosquito truck cruising down the road it was embarrassing but after about 10-15 times of doing that the smoking went away. Checked my plugs and I'm happy to report all my cylinders are seated.
these are the instructions for what you ordered. they come with the kit and are also hot-linked on the product page of the website. please read them and then let me know any questions regarding it you may have.
provided they are followed you will have a correctly functioning catch can system with integrated pcv control
Looks pretty straight forward. The only thing I don't have is the grommet in the driver side valve cover to place the fixed orfice PCV valve you sent with the kit. They are aftermarket valve covers. Does someone make a coupler for this PCV valve so I can just place in-line with the catch can?
Looking at the catch can, it appears to have a rubber flap on the breather acting like a check valve for vacuum. Looks like at idle I have more blow by than I do vacuum. (See video) When I rev and hold at 2000-3000, blow by goes away. I put a sealed oil air separator to help block any oil that might try to backfeed in the fresh air line. I can tell you the mist coming from the catch can breather smells like pure gas.
The PCV flow can be adjusted. Email me if you have not yet for those instructions.
Originally Posted by bunkerbuster
https://www.youtube.com/watch?v=vnn-_Sh4o7g
Originally Posted by bunkerbuster
Looking at the catch can, it appears to have a rubber flap on the breather acting like a check valve for vacuum. Looks like at idle I have more blow by than I do vacuum. (See video) When I rev and hold at 2000-3000, blow by goes away. I put a sealed oil air separator to help block any oil that might try to backfeed in the fresh air line. I can tell you the mist coming from the catch can breather smells like pure gas.
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LS3 PCV routing without valley pan nipple 
