catch can hose route question
Thread Starter
Racer
Joined: Jul 2012
Posts: 261
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From: Tucson AZ
catch can hose route question
Ok so I did some research before and added a catch can a few years ago and a shop here in Tucson that was looking over a short I had from my alt to starter 6 months back noticed my catch can. This shop races cars all over USA and stated that they had a catch can on all of there race cars. He said that my house routing was wrong and said he would re route it for free. I told him ok so he routed it as follows: (Catch can has 3 ports) Intake hose line right before TB to top of catch can, valley cover line has a T in line and it goes to side of catch can and to the Passenger valve cover, 3rd line goes to driver valve cover that was capped from factory, and Intake manifold was capped off.
This does not seem right to me shouldn't the intake line go to the pass valve cover like the factory then valley cover line to catch can then back to intake manifold. Then drivers valve cover to catch can if I want use the 3rd port on the catch can or should the drivers valve cover just be capped?
This does not seem right to me shouldn't the intake line go to the pass valve cover like the factory then valley cover line to catch can then back to intake manifold. Then drivers valve cover to catch can if I want use the 3rd port on the catch can or should the drivers valve cover just be capped?
Race Director
Joined: Mar 2005
Posts: 10,399
Likes: 26
From: Austin Texas
What car is the catch can on?
LS2 or LS3 doesn't need a 3 port catch can. 2 openings are all that's needed. One line from fitting on the valley cover to the catch can, the other from the catch can to the fitting after the throttle body.
The valve cover lines are NOT for REMOVING fumes from the crankcase, they are for filtered make up air to ENTER the crankcase.
The valve cover line could pressurize and vent oil fumes under extreme conditions so a second separate catch can could be added between the valve cover and the fitting BEFORE the throttle body.
LS2 or LS3 doesn't need a 3 port catch can. 2 openings are all that's needed. One line from fitting on the valley cover to the catch can, the other from the catch can to the fitting after the throttle body.
The valve cover lines are NOT for REMOVING fumes from the crankcase, they are for filtered make up air to ENTER the crankcase.
The valve cover line could pressurize and vent oil fumes under extreme conditions so a second separate catch can could be added between the valve cover and the fitting BEFORE the throttle body.
Thread Starter
Racer
Joined: Jul 2012
Posts: 261
Likes: 0
From: Tucson AZ
What car is the catch can on?
LS2 or LS3 doesn't need a 3 port catch can. 2 openings are all that's needed. One line from fitting on the valley cover to the catch can, the other from the catch can to the fitting after the throttle body.
The valve cover lines are NOT for REMOVING fumes from the crankcase, they are for filtered make up air to ENTER the crankcase.
The valve cover line could pressurize and vent oil fumes under extreme conditions so a second separate catch can could be added between the valve cover and the fitting BEFORE the throttle body.
LS2 or LS3 doesn't need a 3 port catch can. 2 openings are all that's needed. One line from fitting on the valley cover to the catch can, the other from the catch can to the fitting after the throttle body.
The valve cover lines are NOT for REMOVING fumes from the crankcase, they are for filtered make up air to ENTER the crankcase.
The valve cover line could pressurize and vent oil fumes under extreme conditions so a second separate catch can could be added between the valve cover and the fitting BEFORE the throttle body.
Race Director
Joined: Mar 2005
Posts: 10,399
Likes: 26
From: Austin Texas
The point is that the valve covers are not supposed to be connected to the vacuum source at the valley cover. That's why the valley cover is connected behind the throttle body and the valve cover is not.
Thread Starter
Racer
Joined: Jul 2012
Posts: 261
Likes: 0
From: Tucson AZ
Ya I know that now I'm saying Is it ok to feed both valve covers fresh air or is just one good enough? I know there two seperate systems but would there be any benifit for the second system to send air to oth valve covers instead of just the one?
Race Director
Joined: Mar 2005
Posts: 10,399
Likes: 26
From: Austin Texas
GM engineers seem to think that one fitting on one valve cover was sufficient.
The only time the fresh air in should function is low engine speed under high vacuum. If the PCV vacuum pulls more air from the crankcase than is coming from ring blowby then the valve cover line allows more air into the crankcase to keep it at neutral pressure.
The only time the fresh air in should function is low engine speed under high vacuum. If the PCV vacuum pulls more air from the crankcase than is coming from ring blowby then the valve cover line allows more air into the crankcase to keep it at neutral pressure.
