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Correct breather setup

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jifop

Number of posts : 58
Location : Hertfordshire, UK
Registration date : 2016-05-22

Correct breather setup

Post by jifop on Tue Sep 06, 2016 4:01 pm

Hey chaps, I'm looking for some breather advice on a 302 v8.

Currently I have a right angled pcv in each rocker cover which pipe to a breather tank also my holley four barrels pcv port is connected to the manifold vacuum port.

I'm assuming this isn't correct but I'm not sure what is correct and could this cause over pressure in the crankcase?

Should one pcv goto the holley and one to the breather?
Should there not be two pcvs at all?
Should I block the holley pcv port off and leave the two pcvs going to the breather box?

Argh

Thanks again...
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Seth G
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Re: Correct breather setup

Post by Seth G on Tue Sep 06, 2016 8:11 pm

I'm not a v8 expert, but afaik, one valve cover should have a vented filler cap and the other should have the pcv. It sounds like you maybe don't have the right valve cover on the drivers side? Where are you filling the engine with oil? The PCV should go to the port on the holley or the carb spacer so the crankcase fumes are evenly distributed in the engine. If there is nothing else connected to the manifold port, it should be plugged.
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donivan65
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Location : San Diego, California
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Re: Correct breather setup

Post by donivan65 on Tue Sep 06, 2016 9:18 pm

The PCV is taking the fumes out of the oil pan,,,,,,,so it can be be in any valve cover or valley pan under the intake manifold,,,,,and it needs airflow in, usually through a vented oil filler cap or a pipe connected to the air cleaner into the valve cover,,,,,you need full vacuum to the PCV,,,,,,and there might be a source on the intake and carburetor depending on if that engine also provided vacuum to a power brake booster at one time,,,,
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jifop

Number of posts : 58
Location : Hertfordshire, UK
Registration date : 2016-05-22

Re: Correct breather setup

Post by jifop on Wed Sep 07, 2016 12:54 pm

Thanks guys, I'm going to route the pcv in one valve cover to the pcv port on the holley and I'll run a pipe from the other to the air filter!
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donivan65
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Re: Correct breather setup

Post by donivan65 on Wed Sep 07, 2016 1:37 pm

Chevy does stuff like this to let the valve cover get its air from the air cleaner,,,,,


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Seth G
Vintage-Vans Listings Manager
Vintage-Vans Listings Manager

Number of posts : 1726
Location : Anacortes, WA
Age : 44
Registration date : 2013-04-24

Re: Correct breather setup

Post by Seth G on Wed Sep 07, 2016 6:50 pm

You should only have one pcv. Think about flow, it comes from one place and goes to another. On an inline it's front to back crankcase vent flow, on a v8 it's the same but split between the 2 sides. The fill/vent is on the drivers side on the 302 b/c it's closer to the front, for convenience when filling the engine with oil. If there's no port for the pcv on the carb or spacer then it should be taken to the manifold. On the engines after maybe 68 or so, with inlines at least, they put a nipple on the fill/vent cap that went to the air cleaner assy. If this is inconvenient b/c the air cleaner assy doesn't have a port then the oil fill/vent cap can be replaced with an earlier cap w/o the nipple.

Don, that's insanity Smile And how does that fit with in the doghouse? Seems like there may be a vacuum there at times fighting the pcv... or does it reverse flow b/c of the pcv outlet and velocity?


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