PCV Valve - Why?

[bitsilly]

Building my 383 stroker chevy and have Edelbrock covers. Also have two breathers to go in the covers. Question is if the sump area breaths through these breathers, if I fit a PCV valve, won't the pressure just vent through the path of least resistance, ie the other breather (from what I can see, just a box with a brillo in)! So what is a PCV valve all about? Do I need one? To make it work do I block off the other breather?
Please excuse my ignorance, but it gets worse, where does the oil go in????
Cheers!
Hope this is the right forum

[dave]

Hi bitsilly.
PVC stands for positive Crankcase Ventilation, what it does is allow the carb to draw some air from inside the engine and the breather is there to allow the air to get in. It is there because some compression will always seep past the rings and possiblty the valve guides and if this extra air is not drawn off it could blow seals. Just fitting a breather will allow it to vent but you could get oil vapour blowing through the breathers which in a short space of time will make a mess. Race engines that don't run PCV usually run the breathers into catch tanks to stop the oil getting on to the track.

......Or something like that.:thumb:

[bitsilly]

Ahhhhhhhhhhh I see!
Cheers Dave
Is the resistance of the valve standard or do I need to do research again? For example, the suction which pulls in the oil laden air, could it be doing something else? Does it need to be balanced with somthing else etc.
XXX
Grasshopper

[dave]

A PCV valve is a PCV valve, no need to worry about volume of suction etc. If you are short of a take off the you could always "T" off the servo feed.

[bitsilly]

Thanks Dave
PS Where does the oil go in?

[dave]

Pull out either the Breather or the PCV and (Gently) pour it in there.

[rich]

Found a little article that explains things well.




PCV VALVE

Definition: The Positive Crankcase Ventilation valve is an emissions control device that routes unburned crankcase blowby gases back into the intake manifold where they can be reburned. The PCV system is one of the oldest emission control devices, and also one of the most beneficial. Besides totally eliminating crankcase emissions as a source of air pollution, the constant recirculation of air through the crankcase helps remove moisture which otherwise would cause sludge to form. Thus the PCV valve extends the life of the oil and engine. The PCV valve requires little maintenance. The valve and filter should be replaced somewhere around 30,000 to 50,000 miles.


l

[bitsilly]

I do love this club!

Cheers

[MarkT]

If you can, instead of having a mesh breather in the other valve cover, have a breather tube which vents into the air filter housing, between the filter element and the carb.

This will allow the PCV to vent the crankcase at low revs and any blow-by gasses to be 'sucked up' at higher revs.

brgds

Markt

[Pictus]

the pcv is like dave said to stop the crankcase brething to atmosphere it has to go throught the engine first when this is done on a ci engine there is a risk of the engine running from the fumes that comes out of the crank case and when this happens there is no way of shutting the engine oof it is freaky to see and the engine does not come out of it alive the engine will run until it blows up or runs out of tasty fumes and sods law dictates it is the first one
i think it is to do with emissions that it is fitted modern cars everything goes through the engine if it brethes they stuff it in the engine intake
well excuse the usless information
im going to shut up now and return to my corner (HERE HERE)

Warren

oh yeah i pick up the engine for the car in 8 hours time and i cant wait