Positive Crankcase Ventilation
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Joined: Jan 2005
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Positive Crankcase Ventilation
I need some input on how to hook up positive crankcase ventilation. I have a 77 351W thast i have taken everything off and just added a 4bbl intake manifold and Holley carb.and plan just to put an after market round air cleaner. Where do the lines from both of the valve covers go now? Which one needs a PCV valve? Breather caps? What am I trying to accomplish? Also, my Holley has a vacuum tube going to the electric choke. Where does that connect to?
Fleet Mechanic
Joined: Aug 2002
Posts: 1,899
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From: Raleigh USA
If I remember correctly the PCV valve slides into the oil cap on the driver's side valve cover and is hooked up to the large manifold vac port. The vacuum line on the choke is for the choke pull-off and that goes to manifold vac also. You can put the breather cap on the pass side valve cover
Posting Legend
Joined: Sep 2001
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Moved to proper forum.
The PCV should go to a large port on the carb base NOT on the vacuum tree. The large port on the vacuum tree is for the brake booster. The vapors from the PCV system will rot out the other vacuum lines if connected to the vacuum tree. The vacuum tree also does not spread the airflow over multiple cylinders like the carb port.
You can put a breather cap on the other valve cover but it should be connected to a filter inside the OEM aircleaner.
DO NOT run an open air cleaner on a daily driver vehicle. Open air filters should only be used on show cars and trailer queens. A properly configured OEM type air filter box will give much better performance and economy on a vehicle that is actually used for something.
The PCV should go to a large port on the carb base NOT on the vacuum tree. The large port on the vacuum tree is for the brake booster. The vapors from the PCV system will rot out the other vacuum lines if connected to the vacuum tree. The vacuum tree also does not spread the airflow over multiple cylinders like the carb port.
You can put a breather cap on the other valve cover but it should be connected to a filter inside the OEM aircleaner.
DO NOT run an open air cleaner on a daily driver vehicle. Open air filters should only be used on show cars and trailer queens. A properly configured OEM type air filter box will give much better performance and economy on a vehicle that is actually used for something.
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