Better flowing LS6 PCV setup?
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TECH Senior Member
Joined: Jan 2004
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From: St.Charles MO
Better flowing LS6 PCV setup? So as well all know the LS6 PCV system(green) vents from under the intake instead of using tubes from the top of both valve covers like the LS1 setup. So with the LS6 PCV system you still have the "fresh air" tube(Red) connecting the pass. side valve cover to the throttle body (which still lets oil through, but Ill get to that later). Now that leaves the drivers side with nothing. While this doesn't seem to be a huge problem (haven't seen anything bad directly related to this) why not just run a line from the drivers side to the passenger side like the LS1 setup(blue)? I don't see how this could hurt, plus it lets the drivers side directly vent into the passenger side which gets air from the throttle body.
Pic:
Also what about running a PCV valve in the "fresh air" tube that runs from the valve cover to the throttle body? (I know a catch can will work here as well, but Im just wondering as I have an extra PCV valve).
Pic:
Also what about running a PCV valve in the "fresh air" tube that runs from the valve cover to the throttle body? (I know a catch can will work here as well, but Im just wondering as I have an extra PCV valve).
The fresh air tube is there to let air into the crankcase, not the other way around. You dont want your PCV to be high flow, you want it so it does its job and nothing more. The LS6 draws oil vapors from the valley rather than the valve covers. It still vents the crankcase and relieves pressure. But since it draws from the valley instead of the valve covers, there is less oil to be pulled through the system. So less oil equals less oil burned off. The easy fix to a LS1 PCV setup is to run the fixed orifice valve off the trucks. Instead of the ball/spring type its just a pinhole so that overall less goes into the intake
Thread Starter
TECH Senior Member
Joined: Jan 2004
Posts: 5,798
Likes: 16
From: St.Charles MO
I probably should have posted this in the OP to clarify some things, this is from this catch can thread, post #394:https://ls1tech.com/forums/generatio...ing-ok-20.html
Hence me connecting both valve covers to get that drivers side some flow.
And it lets oil get by to the throttle body as well, by putting an PCV valve there it may stop some of the oil from getting by.
Understanding the evolution of the LS series
crankcase ventilation system
I'll address GM's path to improving the oil ingestion issue, but the trade off is less effective crankcase evacuation. The goal of balancing proper evac with ever stricter EPA emission rules makes this a trade-off.
First with the introduction of the GenIII LS1 in 1997. The crankcase evac route was drawing it from both valve covers at the rear of each with the fresh make up air drawn from the top of a tube on the throttle body. This allowed a great deal of oil intrusion from both the valve covers & through reversion into the TB in front of the blade.
The next revision came with the LS6 and the valley cover. This helped some with the oil ingestion, but the trade-off was a far less effective crankcase evac as the drivers side valve train got virtually no flow through to flush & evac the harmful combustion byproducts, and the early valley covers allowed to much oil to be drawn out with the gasses. Enter the LS2 and a redesigned valley cover with a baffle system. This worked quite well and minor changes to the newer releases helped as well. Leaving us with the same issue of the drivers side valvetrain not being flushed properly, but the 90mm TB had the fresh air tube eliminated and the make-up air drawn from the intake air bridge. This still allows some ingestion at WOT when the intake manifold vacuum is at its lowest. The L99 then went to drawing from rear of the drivers side valve cover and a still further improved baffle in the valve cover. This solution at least allows proper flushing on both banks and the crankcase itself. Picture the fresh air entering the front of the passenger side valve cover, flowing around the rocker arms, down the pushrod valley, through the crankcase, up the drivers side pushrod valley, around the rocker arms, and exiting the rear of the drivers side valve cover and pulling (flushing) the harmful combustion byproducts out. The problem is the flow is limited and the evacuation still inadequate. When allowed to flow at an effective rate the oil ingestion rises and the problems caused (listed in the earlier posts) are still an issue.
Also, the LS3 STILL pulls from the valley cover which is not all bad except the fixed orifice is to restrictive to allow proper flow.
crankcase ventilation system
I'll address GM's path to improving the oil ingestion issue, but the trade off is less effective crankcase evacuation. The goal of balancing proper evac with ever stricter EPA emission rules makes this a trade-off.
First with the introduction of the GenIII LS1 in 1997. The crankcase evac route was drawing it from both valve covers at the rear of each with the fresh make up air drawn from the top of a tube on the throttle body. This allowed a great deal of oil intrusion from both the valve covers & through reversion into the TB in front of the blade.
The next revision came with the LS6 and the valley cover. This helped some with the oil ingestion, but the trade-off was a far less effective crankcase evac as the drivers side valve train got virtually no flow through to flush & evac the harmful combustion byproducts, and the early valley covers allowed to much oil to be drawn out with the gasses. Enter the LS2 and a redesigned valley cover with a baffle system. This worked quite well and minor changes to the newer releases helped as well. Leaving us with the same issue of the drivers side valvetrain not being flushed properly, but the 90mm TB had the fresh air tube eliminated and the make-up air drawn from the intake air bridge. This still allows some ingestion at WOT when the intake manifold vacuum is at its lowest. The L99 then went to drawing from rear of the drivers side valve cover and a still further improved baffle in the valve cover. This solution at least allows proper flushing on both banks and the crankcase itself. Picture the fresh air entering the front of the passenger side valve cover, flowing around the rocker arms, down the pushrod valley, through the crankcase, up the drivers side pushrod valley, around the rocker arms, and exiting the rear of the drivers side valve cover and pulling (flushing) the harmful combustion byproducts out. The problem is the flow is limited and the evacuation still inadequate. When allowed to flow at an effective rate the oil ingestion rises and the problems caused (listed in the earlier posts) are still an issue.
Also, the LS3 STILL pulls from the valley cover which is not all bad except the fixed orifice is to restrictive to allow proper flow.
And it lets oil get by to the throttle body as well, by putting an PCV valve there it may stop some of the oil from getting by.
JD_AMG
What is described in the first post will work & isn't a bad idea. It guarantees fresh air flow also from the driver side head & the added PCV in the fresh air line will help to keep oil from entering through the TB. Just check the valve from time to time to make sure it isn't stuck closed (fresh air PCV valve open toward valve cover). There's nothing incorrect w/ what is described there.
What is described in the first post will work & isn't a bad idea. It guarantees fresh air flow also from the driver side head & the added PCV in the fresh air line will help to keep oil from entering through the TB. Just check the valve from time to time to make sure it isn't stuck closed (fresh air PCV valve open toward valve cover). There's nothing incorrect w/ what is described there.
