Dumb question on PCV routing etc

Whaler · #1 (**permalink**) 06-21-2002, 12:14 PM

2 questions..........

1) Where should the PCV in the valve cover route to?

2) Where should the valve cover breather cap nipple route to?

I have the Ford Motorsport breather cap on one valve cover (came with the Cobra valve covers) and I have the PCV in the other valve cover grommet.

Now I can route to the.........

1) Nipple on the backside base of the carb base.

Or

2) I can go up into a nipple on the bottom backside of my 9" K&N filter base. The 3/8 rubber hose easily fits inside the nipple.

Really just wondering if there is a preference/standard as to what should go where.

Thanks

Tim

cwmcobra · #2 (**permalink**) 06-21-2002, 05:12 PM

Route it to the PCV port on the carburetor. Do you have a carb. or EFI? If a carb, there should be a PCV port on the front in the carb base.

Hope this helps!

Chuck

Mr.Fixit · #3 (**permalink**) 06-21-2002, 05:34 PM

I like to run the pcv into the intake tract above the throttle blades so as to not pull vacuum at low rpm's which can just help oil get pulled into the intake (especially with aftermarket valve covers which have piss poor baffling). You really need the pcv at rpm when blowby is happening. At rpm, the vacuum signal is the same above and below the throttle blades. At idle, there is a ton of vacuum below the throttle. SO if you run it into the carb vacuum nipple, you will pull more air through the PCV at idle, but the same amount at RPM. That can allow more oil to get pulled through the pcv and burned in your engine, at idle. That's the way I like to do it, but you can just get a 3/8" TEE fitting and splice it into any vacuum line you want and it will still work, but oil control may become an issue. All this is assuming smog exempt status, so keep that in mind since a PCV is a smog control device.

Whaler · #4 (**permalink**) 06-21-2002, 06:10 PM

Thanks for the replies ,looking at it now.
Yes I have the carb, a holley 850 and I am using the edelbrock RPM intake

Tim

Mike Madonna · #5 (**permalink**) 06-21-2002, 07:48 PM

Could you tap into the same manifold vacuum source that's used for the power brake booster? For example, use a "tee" fitting at the base of the carb., one side for the PCV & the other for the brake booster. Or does the brake booster need it's own vacuum source? Just wondering....

Thanks

gsharapa · #6 (**permalink**) 06-21-2002, 08:59 PM

Do not use the same fitting (tee) that you are using for your brake booster as it will take away from the brakes.

I have one going to the base of my dominator carb and a hose going off the other valve cover to an Oil breather tank. Nice set up!

boxhead · #7 (**permalink**) 06-21-2002, 10:20 PM

Hiya Tim.
Your pcv breather should go into the underside of your air filter.
Do not attach it to a direct vacuum below the throttle blade ie:base of carb or brake booster vacuum port.
If you fit it after the throttle blade you will have an excessive amount of vacuum, drawing too much oil through your pcv.
you will also have unmetered air being drawn into the manifold which will result in a lean running fuel mixture.
And you dont want to run your engine lean.

Whaler · #8 (**permalink**) 06-22-2002, 10:51 PM

Thanks Boxhead

Thats how I have done it....route it back to the topside of the carb into the air cleaner nipple in the filter base.

The breather cap I may just stick it down to the ground or to a nice catch can.

Tim

Jack21 · #9 (**permalink**) 06-25-2002, 10:12 AM

The PCV (positive crankcase ventilation) creates a small amount of airflow and vacuum in the crankcase to remove oil vapor, and burn it in the engine. This hose is routed to the PVC inlet on the base of the carb, and should be a 3/8" hose fitting. This distributes oil vapors evenly to all cylinders. To restrict the airflow volume, put a small orifice restrictor in line with the PCV. The gapless ring folks recommend this because of the improved vacuum when using these rings.

The breather hose gets routed to the breather hose fitting on the air cleaner. This gets clean air into the engine. Buttoned up, this line is always under vacuum. When oil vapors start coming out the breather, you have blow by taking place (ring seal). Some breather caps don't have this, and just inhale from ambient air. Meaning, it's nice, but not necessary.

The vacuum line for the brakes should not be connected to the PCV line. There should be a vacuum port on one of the intake manifold runners for the brakes. On the Edelbrock Performer RPM 351W, it's on the #4 runner.

Whaler · #10 (**permalink**) 06-26-2002, 05:20 AM

Hello Jack 21
Thanks for your input as well

http://www.hastingsfilter.com/engine...tsb_94-2r.html

Tim

Bob In Ct · #11 (**permalink**) 06-26-2002, 07:37 PM

I have a 351w with Performer RPM manifold and Holley 80508 750 CFM carb. Does this carb have a port for a PCV connection? Does it have a port for the power brake unit?

Thanks, Bob

Mike Madonna · #12 (**permalink**) 06-26-2002, 08:09 PM

I'm in the same boat you are.... same manifold and carb. Carb has only one manifold vac. port at rear of base, and on my application that is used for PB booster. The other manifold vac. port is under the primary bowl on the pass. side. The ports are different sizes, smaller in the front & larger in the back. I understand that "tapping" the #4 intake runner may lean that cylinder out somewhat.

Mike