I have a fairly lame sbc 350 from a 1970 Corvette, smog heads, garbage RV cam, Holley 600 cfm carb. I'm gonna say max 275 hp on a good day. I have a pcv valve on one valve cover and a breather on the other. There is no oil tube going into the manifold because I replaced the stock iron one with an Edelbrock aluminum one. I put oil in by taking the breather out. This is purely a street application. In fact, it's my daily driver. Nothing fancy - no stud girdles or anything. I recently bought two used finned valve covers at a swap meet. Only one has a breather hole. The other one has no hole. Could I use only a pcv without a breather on the other side? Or do I need a breather AND a PCV valve if my goal is to get long life out of my engine by keeping it clean? I have been told that both are designed to relieve crank case pressure one by creating a way for air to escape (the breather) and the other relieves pressure by creating a vacuum in the crank case (pcv valve) and suck out water. So, the theory goes, having a breather and a PCV would kind of defeat the purpose of the pcv as you would be pulling air through the engine which would lead to lots of oil residue in carb/manifold. I'm grateful for any advice on this.
Not really. The system is so designed that the PCV valve draws "Dirty" air out of the crankcase while the breather allows clean air to go in. If you have no way for clean air to get in I really doubt if it will function well at all.
You need some way to replace the air being pulled out of the crankcase by the PCV . A breather in the opposite valve cover is needed to accomplish this. Without this, you'll suck the seals and/or engine gaskets in.
You wont suck your seals and gaskets in as it cant get past atmospheric pressure on the out side of the engine. One issue is your carb. is metered for the flow from the positive crankcase ventilation system. If you don't want to fit a breather to the other valve cover is there a boss on the front of the intake for a filler/breather tube to be retro fitted ? This is a common issue when large journal SB Cheys are made to look like early SJ SB Chevs. JW
A PCV is like your lungs. Air in, air out. If you plug your nose and use your mouth only for air out, what happens?
One thing that is rarely mentioned is that the PCV system draws MOISTURE out of the crankcase too. A tell tale sign of a non working PCV system is the milk chocolate foam that forms around the oil fill or PCV valve (moisture in the oil). If you want water in your engine don't hook up your PCV system properly.
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