Guest nwzeeman Posted February 28, 2005 Share Posted February 28, 2005 I'm nearing the completion of my rebuild of my sbc 350 for my 1978 280Z. The engine is a 4-bolt main out of an 82 pickup. The question I have is do I need breathers in my valve covers? I see valve covers with and without breather holes. My car will be carbureted with no EGR. This car will not be a drag car or racer, just a routine driver. Can someone explain these breathers purpose? I would prefer to buy valve covers without any cutouts, but will put a breather on them if deemed necessary. Thanks for any advice. -Rod Quote Link to comment Share on other sites More sharing options...
awd92gsx Posted February 28, 2005 Share Posted February 28, 2005 In a nutshell, your PCV system draws air through your crankcase. The breathers allow filtered air to be drawn into your crankcase while the PCV system creates a near vaccuum state in your crankcase. Quote Link to comment Share on other sites More sharing options...
Tim240z Posted February 28, 2005 Share Posted February 28, 2005 YEs, you do need breathers, or PCV system. The pressure in the crankcase needs to vent to prevent the pressure pushing on seals and gaskets. You should use a PCV valve and plumb it into your intake. If you just use a breather and your engine has any blowby passed the rings, it will push oily fumes all over your valve covers and engine. Tim Quote Link to comment Share on other sites More sharing options...
Guest nwzeeman Posted February 28, 2005 Share Posted February 28, 2005 Ok, that makes sense....next question would be...do I need to plumb the PCV valve to both valve covers, or is plumbing to one valve cover enough? Thanks again. -Rod Quote Link to comment Share on other sites More sharing options...
Tim240z Posted February 28, 2005 Share Posted February 28, 2005 One side is sufficient. Quote Link to comment Share on other sites More sharing options...
Heavy Z Posted March 1, 2005 Share Posted March 1, 2005 I've read here in a prior post on the subject to use a breather on one side and a pcv on the other side. Good luck. Quote Link to comment Share on other sites More sharing options...
jt1 Posted March 1, 2005 Share Posted March 1, 2005 originally posted by heavy ZI've read here in a prior post on the subject to use a breather on one side and a pcv on the other side. Yep. Breather one side, PCV the other side, baffle under the PCV is a good idea too. Only a full race engine doesn't need a PCV. John Quote Link to comment Share on other sites More sharing options...
Guest tony78_280z Posted March 1, 2005 Share Posted March 1, 2005 I few more questions while we are on the subject. What about those motor pics I've seen in which both sides were plumbed into the intake (I assume both PCV)? Or those where neither were (I assume both were breathers)? Or those airbreathers with plumbing (I asume a PCV with a built in filter/breather)? Hmmmmm? Quote Link to comment Share on other sites More sharing options...
COZY Z COLE Posted March 1, 2005 Share Posted March 1, 2005 Both are breathers on mine. It's been known to emit a whiff of smoke, mostly moisture, after a good spanking run from my cowl induction opening. People either think my engine is on fire or wonder what the Hell is under that hood. LARRY Quote Link to comment Share on other sites More sharing options...
awd92gsx Posted March 1, 2005 Share Posted March 1, 2005 Tony, It could be that they are pulling air through the actual air filter, rather than just a breather. There's also a way to set it up so that you run a NCV type system instead of a PCV system...that might be why they are running 2 tubes to it, also. Quote Link to comment Share on other sites More sharing options...
Mike kZ Posted March 1, 2005 Share Posted March 1, 2005 I've read here in a prior post on the subject to use a breather on one side and a pcv on the other side. Good luck. That's what I have...no problems! Quote Link to comment Share on other sites More sharing options...
Psykovertible Posted March 7, 2005 Share Posted March 7, 2005 i am going to use the vacupan from milodon race products. probably overkill but some things i just take do simply cause dad says i should http://www.milodon.net/new%20images/85700%20.GIF u put two things in the collector or in pipes like a smog pump inlet would be found. those create vaccuum in the crank case that works off of the exhaust gasses passing over them and sucks a vaccum through the breathers in each valve cover. Quote Link to comment Share on other sites More sharing options...
Guest tony78_280z Posted March 7, 2005 Share Posted March 7, 2005 u put two things in the collector or in pipes like a smog pump inlet would be found. those create vaccuum in the crank case that works off of the exhaust gasses passing over them and sucks a vaccum through the breathers in each valve cover.To what purpose? Is this better or just different than other setups? Give us more info, MAN!! Quote Link to comment Share on other sites More sharing options...
Psykovertible Posted March 7, 2005 Share Posted March 7, 2005 as an uneducated guess i would say that it is mostly just different. however, with a big cam that does not build much vaccum......... the exhaust could run the crankcase pressure while the limited vaccum provided bya cam witha small lobe seperation anlge would better run the brake booster. i dont know if my theory is flawed but it seems reasonable that there is only so much vaccum to go around so the less operating on it the better shouldnt be an issue for me casue im gonna order a cam that is about 500 lift with a 112 LSA and a 240-250 duration. should be more than enough vaccum. Quote Link to comment Share on other sites More sharing options...
mtcookson Posted March 7, 2005 Share Posted March 7, 2005 the best thing to do with the pcv systems is to get an external vacuum pump to pump out the gasses and such, especially when boosted. most people see actual hp gains when putting a vacuum on the pcv stuff. i know on race cars they'll actually get put an actual vacuum in there (as in, an actual vacuum pressure) which is supposed to help seal the rings better and get out the gases much faster. (the gases tend to be quite corosive and are usually what cause quick oil deterioration so the more you can get out the better) Quote Link to comment Share on other sites More sharing options...
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