catch can hose routing
Thread Starter
Instructor
Joined: Jan 2011
Posts: 114
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From: tucson az
catch can hose routing
ok so i bought a ebay catch can that had 2 original outlets coming out of side but my friend said it would not work unless we added a 3 outlet, 1 one top so i went with he said and he drilled out a hole on top and added a 3rd vacuum hose connection. I"m wondering if he routed it right? He has the driver side valve cover vacuum connection wrapped around back of intake going into a t connection right at the bottom of the intake vacuum connection. Then he has the passenger side valve cover vacuum connection going straight to the other side of the catch can. the final connection the 3rd is routed from the top of intake connection to the top of the catch can connection. I have never seen 3 hoses coming of any ones catch can but mine! Is this right or wrong? Is this why I now have a vacum leak issues going off and on?
Race Director
Joined: Mar 2005
Posts: 10,399
Likes: 26
From: Austin Texas
The catch can should only be on the line from the valley cover to behind the throttle body. The other line from the valve cover to in front of the throttle body is a separate circuit for make up fresh air into the crankcase.
Plug the additional line and run just the one from the valley cover to behind the throttle body.
Plug the additional line and run just the one from the valley cover to behind the throttle body.
Thread Starter
Instructor
Joined: Jan 2011
Posts: 114
Likes: 0
From: tucson az
The catch can should only be on the line from the valley cover to behind the throttle body. The other line from the valve cover to in front of the throttle body is a separate circuit for make up fresh air into the crankcase.
Plug the additional line and run just the one from the valley cover to behind the throttle body.
Plug the additional line and run just the one from the valley cover to behind the throttle body.
Thread Starter
Instructor
Joined: Jan 2011
Posts: 114
Likes: 0
From: tucson az
And am i suppose to cap off both valve cover holes with vacuum caps or add breather just to one side or both sides?
Thread Starter
Instructor
Joined: Jan 2011
Posts: 114
Likes: 0
From: tucson az
The catch can should only be on the line from the valley cover to behind the throttle body. The other line from the valve cover to in front of the throttle body is a separate circuit for make up fresh air into the crankcase.
Plug the additional line and run just the one from the valley cover to behind the throttle body.
Plug the additional line and run just the one from the valley cover to behind the throttle body.
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Race Director
Joined: Mar 2005
Posts: 10,399
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From: Austin Texas
Stock there is one line from the passenger side valve cover to in front of the TB, that line allows filtered air to enter the crankcase and one line from the valley cover to behind the TB, that line allows excess pressure (and oil fumes) flow from the crankcase to the intake manifold.
Two separate circuits. Valve cover line allows air in, valley cover allows pressure out.
Two separate circuits. Valve cover line allows air in, valley cover allows pressure out.
Former Vendor
Joined: Apr 2006
Posts: 2,470
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From: Portland OR
St. Jude Donor '10-'11-'12
Yes the direction of flow is from valley pan to intake.. your putting the can in the middle of that to clean the air flow...
the valve covers are the source of clean air for the crank case... You need flow in one direction to properly evacuate it.
You can use breather on the valve covers or use the clean air return system the way is was supposed to be used. It draws clean air from a line off the valve cover to the intake tract somewhere.. it needs to be filtered air so it comes after the air cleaner.... If you put a check valve in that line you will take care of any reversion that might try to happen.
Race Director
Joined: Mar 2005
Posts: 10,399
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From: Austin Texas
Don't put a "breather" on either valve cover line, you'll fail the visible inspection. Cap one and run the other to after the air filter /before the throttle body.
Thread Starter
Instructor
Joined: Jan 2011
Posts: 114
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From: tucson az
Ok i get it now. So what do i do to tap into the maf and tb boot to connect that hose back on to the system. I acciddently threw away the old plastic line from tb to valve cover. What could I use to replicate that piece or what is the gm part number for that line to passenger valve cover?
