purpose of a PCV or breather flange - newbee

[kgs365]

other then to let it breath can someone explain if a PCV or breather flange is needed...here is the build 390 FE edlebrock performer RPM intake , edelbrock 60069 heads.compression around 9:2..edelbrock 750 performer carb and performer cam..easy street build not looking for huge horsepower...the intake has the provision for the PCV but id have to drill it out and tap the bolts...so before that exercise perhaps an expert can explain if i need it or not?

[xlr8or]

The back of your carb base probably already has a port for that so no need to modify the manifold.
The idea of it is to allow excess crankcase pressure to escape but not into the open air. It recycles it through the intake and burns it.

[Argess]

Let's say you only have a vent on the engine. Eventually, goopy yellow stuff, which I think is detergents and other additives from the oil, will start to come out the vent due to a little blowby. At this point, if you remove valve cover oil caps, you will find the underneath of the caps covered with this yellow stuff as well. Ask me how I know? Because that's how I had my engine set up for a while.

Eventually,, I installed a PCV system and ever since then, no more yellow goopy stuff. It gets sucked in via the PCV and is burnt vs slowly building up inside the engine.

There's a lot of different ways to hook up a PCV system. Depends on your manifold, valve covers, carb, carb space, etc. I don't find it a touchy system, so I'm sure you can deviate a bit and still get it to work.

[kgs365]

great guys..thats what i was looking for thanks!

[Tony Radford]

I think that creating negative pressue in the crankcase helps prevents seals such as the rear main seal from leaking. I had a lot of trouble with that before running a PCV. Breathers on the valve covers didn't get it. I'm talking a Windsor, so maybe it's a different story with an FE.

[CSX4279]

Maybe you FE wizards can help on this one...newly rebuilt cast iron 427 sideoiler. Pentroof (non vented) valve covers..breather oil cap on oil fill tube at front of intake manifold..vent tube at manifold rear to "puke tank". Tank has both oil pan return AND vent road draft tube. I get oil leaking from draft tube AND liquid oil in puke tank.....being fed up with constant oil on my garage floor AND oil all over the chassis, I blocked off the puke tank (keeping it for looks only on CSX4000 firewall) and ran a PVC valve to the carb. Leaking stopped but when idling, it's like a five alarm fire with all the exhaust smoke and stink. So much so that the sidepipes actually had black LIQUID oil in them. I might add that I am running a solid roller and as a result the intake valley baffle pan could not be installed due to lifter height.....
Any ideas on how I can stop most of this blowby without changing the non-vented valve covers OR do I have no choice? Motor only has 1000 miles on it.
Thanks Bob

[rokndad]

Originally Posted by CSX4279

Maybe you FE wizards can help on this one...newly rebuilt cast iron 427 sideoiler. Pentroof (non vented) valve covers..breather oil cap on oil fill tube at front of intake manifold..vent tube at manifold rear to "puke tank". Tank has both oil pan return AND vent road draft tube. I get oil leaking from draft tube AND liquid oil in puke tank.....being fed up with constant oil on my garage floor AND oil all over the chassis, I blocked off the puke tank (keeping it for looks only on CSX4000 firewall) and ran a PVC valve to the carb. Leaking stopped but when idling, it's like a five alarm fire with all the exhaust smoke and stink. So much so that the sidepipes actually had black LIQUID oil in them. I might add that I am running a solid roller and as a result the intake valley baffle pan could not be installed due to lifter height.....
Any ideas on how I can stop most of this blowby without changing the non-vented valve covers OR do I have no choice? Motor only has 1000 miles on it.
Thanks Bob

Are you sure you had the overflow tank plumbed properly. The high bib on the passenger side goes down to the frame to scavange gasses like a road tube, the lower bib on the same side goes to the return oil line to the top of your "tee" oil pan (aviaid or similar). The idea is condensed oil vapors will sweat to the bottom of the tank and flow back into the pan.

The smaller bib on the driver's side receives the hot gasses from your transmission and the lower larger one accepts your hose from the rear of the intake manifold.


You also should have a basket with a screen of stainless steel wool in it to prevent excess slosh up into your puke line.


I used to have that setup with the non-vented pentroofs and the vent cap on the front intake manifold oil fill tube and never had the problems you're experiencing. Oh, and no PCV of any kind.

[CSX4279]

Thanks much for your quick reply ROKNDAD. I have the mesh basket which the engine builder never reinstalled. I will install it and make sure my puke tank is plumbed exactly as you say and nix the PCV valve. I wonder also if the lack of lifter valley baffle pan(due to height of solid roller lifters) AND/OR running 65-70 PSI hot oil pressure contributes in any way? Thanks again and I also can be reached at sideoilerbob@aol.com if any easier.
Bob