Breather hoses question
Thread Starter
Safety Car
Joined: Mar 2007
Posts: 3,518
Likes: 37
Breather hoses question
I have this LS2 with an older Procharger style A&A setup on it. Problem is I get oil in the aircleaner under boost. On the track it let in lots of oil.
Looking at the new A&A install instructions here is the plan to change the system:
1. Put on a catch can with intake hose from the pan under the manifold, out hose to PCV or check valve then to the manifold nipple which is currently capped.
2. Run the hose from the air cleaner to the top of the oil fill cap, should have much less oil vapor or oil.
What do I do with the hoses to the rocker covers? Just cap them?
Which should I put on? A PCV or a check valve on the manifold?
Should I put a check valve on the hose to the air cleaner to keep vapor from venting there?
Looking at the new A&A install instructions here is the plan to change the system:
1. Put on a catch can with intake hose from the pan under the manifold, out hose to PCV or check valve then to the manifold nipple which is currently capped.
2. Run the hose from the air cleaner to the top of the oil fill cap, should have much less oil vapor or oil.
What do I do with the hoses to the rocker covers? Just cap them?
Which should I put on? A PCV or a check valve on the manifold?
Should I put a check valve on the hose to the air cleaner to keep vapor from venting there?
Banned Scam/Spammer
Joined: May 2007
Posts: 15,685
Likes: 1,330
From: Machineguns, because I don’t compromise
What did you find? I'm about to instal an incomplete kit and will address this same issue.
I've already got a catch can. I'm thinking that I'll run both the valley cover and valve cover lines through a check valve on it's way to the catch can, which then goes towards the airfilter inlet.
I've already got a catch can. I'm thinking that I'll run both the valley cover and valve cover lines through a check valve on it's way to the catch can, which then goes towards the airfilter inlet.
Thread Starter
Safety Car
Joined: Mar 2007
Posts: 3,518
Likes: 37
What did you find? I'm about to instal an incomplete kit and will address this same issue.
I've already got a catch can. I'm thinking that I'll run both the valley cover and valve cover lines through a check valve on it's way to the catch can, which then goes towards the airfilter inlet.
I've already got a catch can. I'm thinking that I'll run both the valley cover and valve cover lines through a check valve on it's way to the catch can, which then goes towards the airfilter inlet.
There are different options depending if you are willing to vent to atmosphere or want to get the venting back into combustion. For me I might just put the catch can on the hose between all those lines and the air filter in front, check to see if there is much vapor. But it would be nice to not have any hose with possible oil vapor in the air filter or anywhere before the MAF to prevent fouling of that. I thought about putting the catch can in past those hoses and dumping it all in the manifold with a PCV valve but that cuts off all venting under boost because the PCV closes with boost.
So I have some things to try out. But the issue is pretty thoroughly gone over in other posts; I just wanted to drop this new thread. If someone does have the concise definitive answer that would be nice if just happen to be browsing.
Banned Scam/Spammer
Joined: May 2007
Posts: 15,685
Likes: 1,330
From: Machineguns, because I don’t compromise
Good point about not wanting the oil vapor going past the MAF and then the rest. Ick.
The only thing about putting a check valve and then right behing the throttle body into the manifold is that when the car goes into boost you now have a pressurized crankcase without the benefit of vacuum like a N/A car has.
I just read in another thread that Racetronix has a harness that will let you convert your A.I.R. pump into an evac pump. If so, that opens up another set of doors. I've gotta check that out.
One way or the other, I'd like to always have a vacuum being pulled whether from the blower intake or some kind of pump.
The only thing about putting a check valve and then right behing the throttle body into the manifold is that when the car goes into boost you now have a pressurized crankcase without the benefit of vacuum like a N/A car has.
I just read in another thread that Racetronix has a harness that will let you convert your A.I.R. pump into an evac pump. If so, that opens up another set of doors. I've gotta check that out.
One way or the other, I'd like to always have a vacuum being pulled whether from the blower intake or some kind of pump.
Thread Starter
Safety Car
Joined: Mar 2007
Posts: 3,518
Likes: 37
Good point about not wanting the oil vapor going past the MAF and then the rest. Ick.
The only thing about putting a check valve and then right behing the throttle body into the manifold is that when the car goes into boost you now have a pressurized crankcase without the benefit of vacuum like a N/A car has.
I just read in another thread that Racetronix has a harness that will let you convert your A.I.R. pump into an evac pump. If so, that opens up another set of doors. I've gotta check that out.
One way or the other, I'd like to always have a vacuum being pulled whether from the blower intake or some kind of pump.
The only thing about putting a check valve and then right behing the throttle body into the manifold is that when the car goes into boost you now have a pressurized crankcase without the benefit of vacuum like a N/A car has.
I just read in another thread that Racetronix has a harness that will let you convert your A.I.R. pump into an evac pump. If so, that opens up another set of doors. I've gotta check that out.
One way or the other, I'd like to always have a vacuum being pulled whether from the blower intake or some kind of pump.
Are the crank case and valve cover vents connected? So if I put a vacuum on the valve cover tube would I feel it at the crank case vent tube (Engine off?)
If so I could connect both valve cover hoses so right and left are same; then vent the oil cap to give those vent. If the crank pan and the valve covers are connected from inside that gives the crank case vent too. Close off the crank case pan vent tube. Vent the oil cap through a catch can then into the air filter?
OR connect the crank case vent through the catch can and through a PCV to the nipple on the manifold behind the throttle body (Closed in boost but crank and valves vented the other way?)
Banned Scam/Spammer
Joined: May 2007
Posts: 15,685
Likes: 1,330
From: Machineguns, because I don’t compromise
The valve covers and valley cover both vent. If you pull a vacuum on the cover, you will feel it on the valley cover nipple.
With that being said, you can just block off the driver side valve cover since it's redundant. the C5Zo6 has that orifice plugged with a rubber stopper, and the passenger side doesn't have the rear nipple (on a Zo6)only the front one that goes to the top of the throttle body.... The C5z mainly breathes from the valley cover.
I don't just want to "vent", I want "vacuum" being pulled all the time to help with all that air moving around under the pistons at high rpm.
Looked on Racetronix's site which has a lot of stuff, didn't see the air pump harness so I guess I'll have to call to ask.
With that being said, you can just block off the driver side valve cover since it's redundant. the C5Zo6 has that orifice plugged with a rubber stopper, and the passenger side doesn't have the rear nipple (on a Zo6)only the front one that goes to the top of the throttle body.... The C5z mainly breathes from the valley cover.
I don't just want to "vent", I want "vacuum" being pulled all the time to help with all that air moving around under the pistons at high rpm.
Looked on Racetronix's site which has a lot of stuff, didn't see the air pump harness so I guess I'll have to call to ask.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Every 2027 Corvette Engine Explained
Joe Kucinski
Designer Imagines A Corvette That Looks More Like a Corvette Than the Corvette
Verdad Gallardo
10 Ugly Corvettes That We Still Kinda Love
Joe Kucinski
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Thread Starter
Safety Car
Joined: Mar 2007
Posts: 3,518
Likes: 37
The valve covers and valley cover both vent. If you pull a vacuum on the cover, you will feel it on the valley cover nipple.
With that being said, you can just block off the driver side valve cover since it's redundant. the C5Zo6 has that orifice plugged with a rubber stopper, and the passenger side doesn't have the rear nipple (on a Zo6)only the front one that goes to the top of the throttle body.... The C5z mainly breathes from the valley cover.
I don't just want to "vent", I want "vacuum" being pulled all the time to help with all that air moving around under the pistons at high rpm.
Looked on Racetronix's site which has a lot of stuff, didn't see the air pump harness so I guess I'll have to call to ask.
With that being said, you can just block off the driver side valve cover since it's redundant. the C5Zo6 has that orifice plugged with a rubber stopper, and the passenger side doesn't have the rear nipple (on a Zo6)only the front one that goes to the top of the throttle body.... The C5z mainly breathes from the valley cover.
I don't just want to "vent", I want "vacuum" being pulled all the time to help with all that air moving around under the pistons at high rpm.
Looked on Racetronix's site which has a lot of stuff, didn't see the air pump harness so I guess I'll have to call to ask.
1. Vent the oil cap (Valve covers) to the air filter, little risk of pulling oil through to air filter due to placement on oil cap.
2. Hose from valley cover to catch can, from catch can to PCV valve, PCV valve to manifold behind throttle body.
This gives vacuum to the valley cover at all times except under boost when the PCV closes to avoid pressurizing the block. While in boost pressure could escape the valley through the valve cover venting. Plan on catch can to get most oil out of the air going through.
