Hy Bob1200, your vacuum source(in your racing system) seems to be the exhaust , so the air separated from the oil gets ejected via exhaust manifold, but it never goes into the combustion chambers,does not go into the intake manifold, just pulled out and away. That system seems excelent. Keeps the oily stuff in the tank, and rids the engine of the bad air, without re-burning unproductive air in the cylinders.

Race cars use crankcase ventilation systems pumbed to a speration tank that seperates oil from crankcase fumes then pumbed to a air injection check valve at the exhaust collector which then creates a vacuum in the crankcase.
The result is better ring sealing and more HP not much but every improvment counts.
systems only works above 4000 rpm.

Hy guys. No quarrel here I just expose my ideas, my style is direct, do not take me wrong. These concepts I took from books, and from viewing racing cars. I read a book by Des Hammil, how to rebuilt and blueprint a 4 cyl engine(probably not exact words, I have the book at home, as well as other Des Hammil books), and also How to built a OHC nissan engine for performance(again, I have the names in my mind, probably not exact,but I have tha book at home.) In those books , they talk about the PCV system and how it is used in racing, I also read extensively on the pollution systems matter, due to the emmissions tests in Ca, and I wanted... (I am that kind of person, I want to understand how a system works, not just put it together)... to know how it works and why, so I can better understand the system, if you know how it works, you do not need more instructions, you can actually deduce how it should work, as opposed to following a map blindly.There is more to the system I did not mentioned, there is no reason to get too specific and specialized, this was supposed to be a pcv valve solution /explanation topic. Sure there can be more crank ventilation avenues, some add a timming chain cover vent, also a oil pan vent, all of which can be connected together to a single bottle or filter , which ussually is located as high as the valve cover(the highest opening of them all, by openings I refer to the vents) The mission for the ventilation system is that name itself, ventilation, re-burning of hydrocarbon charged and by product air...(the stuff that comes out of the block, supposed to be vented out of the cranckcase/block by this system)...is not a mission of the ventilation system, that is a anti-pollution device/idea added to the cranckcase ventilation, to treat the by product charged contaminated with hydrocarbon air that comes out of the block. The PCV valve helps in this area, re-burning of this air, but is not integral part of the ventilation system. You can not do away with ventilation, if you cover all the exits(valve cover and block vent in normal vehicles, oil pan, timming chain vents in racing cars)...the by product air will still come out, imposible to stop, through gaskets, oil cap, oil dipstick, and any available posible avenue of escape. I am not advocating for that, but for an efficient vent system, you do not need the PCV valve system. Your engine does not need to re-burn any of those gases/air coming out of the engine. It is good for the enviroment, yes, but it is not a necesity for the performance of the vehicle at all.The downside of using the PCV system is that you are sending bad air into a area that needs good air, and taking the place in the combustion chambers of clean air that could be there with a better amount of benefit to the ignition event in the engine, as opposed to this charged bad air. I can understand some people might think that I have to be wrong because they assume that something that came with the car is material and necesary for performance, but some things are just added on stuff needed for pollution control, like catalic converters, which are not needed for performance either.(The EGR system is another example, not needed, no efficient exhaust system needs the EGR valve and re-routing of exhaust gases back into the intake manifold) If anybody wants to keep this PCV valve, its oK, I am not advocating anybody to throw it away, just understand the concept and then decide for yourselves. I would recommend to those a little bit reluctant to rid their cars of the PCV valve, to at least, replace it(it's cheap) and also replace it's hose which can and probably is all clogged after years of use. What I would recommend strongly is to disconnect the valve cover to carburetor hose, that one is a no way jose! install a breather filter in it's place, avoid messing up your carburetor.
I can , and will , bring in quotes from my books. (I remember one by memory, page 100 in Des Hammil's book, "how to blueprint and build a 4 cyl engine for performance".)
Jaime.
Have a nice days, brother Datsun fans!

I've seen quite a few race cars or drag race cars with open headers use those crankcase evacuation deals.
They use a one-way valve plumbed into the collector and a tube goes to the valve cover. The flow of exaust gas thru the collector draws air out of the crankcase.

So I guess that this "Road Draft Tube" basically works on the "Venturi" principle, with the air flowing past the end, causing a vaccuum that sucks the fumes out of the crank case.

Chris

Jamie,
I second that statement, I teach this stuff every day. More to the point, I have delt with emission controlls for over 30 years.
honestly, it sounds to me as though somewhere you have gotten some information that is incorrect.
as an aside, before there was a pcv system, engines had what was called a road draft tube. basicly this was a tube about an inch in diameter that hung off the side of the engine, ending at about the bottom of the oil pan. oil caps were vented to allow fresh air in and the crankcase gasses vented out the end ot the tube, it took them a while to figure out that all that oil all over the bottom of one's car came from that road draft tube.

Jaime, you should read an auto mechanics book to get the real scoop on PCV system. Yes, you don't need it, your engine will run OK without it -- but that doesn't mean it is evil. And although it was originally designed for emissions control, it does have some benefits other than emissions.

Hy bro. The PVC or positive cranckcase ventilation is designed to ventilate the engine, that I agree. It does not go in one direction only, that is not right. When driving at slow speeds, engine idle, it goes the path we all know, new air(not new, bad air from the block into the PVC valve)...or contaminated air from block into intake system via hose through PCV valve, and into the engine via air cleaner assembly through hose into valve cover. At high RPM, fast speeds, full throatle, the PCV valve and intake manifold can not absorb the amount of gases that the engine is producing, so the air demands of the engine, demand to excrete this bad air out of the block that normally goes out throgh the block opening into hose and pcv valve into intake will now exit the engine the other way, through the valve cover INTO the CARBURETOR, sending bad air, with low amounts of OXIGEN, full of burnt hydrocarbons into your intake and combustion chambers, not very good nor healthy for your engine, which needs oxigen, not burnt hydrocarbons. At high speeds the block goes into a release mode, needs to get rid off lots of hot burnt gases/ heavy air.By having both exits (block to breather against block to PCV valve, and, valve cover to breather against valve cover to carburetor)... connected to breathers, you asure fresh air into the engine when the block sucks in air(lower speeds, iddle,block takes in air and also releases air), instead of burnt hydrocarbons, and no burnt hydrocarbons into intake system through the carburetor hook up to valve cover. The reason to route this bad air into the carburetor is to burn and re burn these gases before they go into the atmosphere. Since very few of us in the world are looking to make our Datsuns perform well, we are not making any major pollution problems to this world,Very small minority) for that reason,(to see a polluter in progress) drive behind a diesel vehicle and see what pollution is all about. The engine only needs to release all this by product of engine work(gases) out of the block at high speeds, and will take some fresh air at slower speeds, that is what the breathers do, you do not need a PCV system, only a ventilation system for the block, which the breathers do,the intake and burn of this gases is an extra thing not needed for best performance and lasting of your nice expensive carburator. Without the PCV valve, your performance should get better because you do not have gases burnt with no oxigen content invading the space that clean air mixture should be taking inside your intake and combustion chambers.Nor you would have oily gases with no oxigen mixing with gasoline/petrol in your carburetor as a consecuence of this valve cover hose releasing this bad burnt hydrocarbon air into your carburator, space fresh cool air could be using. Imagine a cold air box designed for your car, you want colder air to reach your carburation for proper performance and excelent mixture in the carburetor, then, why would you sabotage all that excelent work(cold air box, ram air) with some hot burnt hydrocarbon saturated low in oxigen air also oily and messy, into the mix?
Think about it, you do not need that bad air,and it will not pollute nothing.The PCV valve is a re burning device (re burning of bad air) , not a necesity, I would say a luxury not needed.

Jaime._____________________________

Well I left mine on despite the odd noise it makes when the engine is not running smoothly - as posted earlier.

I think it is far more elegant to just push the crank fumes back into the motor as intended.

PCV=Positive Crancase Ventalation, the reason it's there is to allow the crankcase to breathe.
think of it this way: for every bit of air that moves through the intake and exhaust manifolds, an EQUEAL amount moves through the crankcase. some of this being blow by past the piston rings.
the pcv system is there to allow fresh air to vent those gasses out of the crankcase, and the pcv valve is there to ensure that the air for venting moves in 1 direction only. the pcv valve is also designed so that if there is a backfire, that the flame will not burn back into the crankcase and cause it to blow up(yes it has happened) there is no bennifit or performance gain from disconecting or modifying the pcv system. there is a slight fuel milage advantage to having one that works because it will take unburned gas and feed it back through the engine. as far as getting oil through the hose into the intake, there is a screen baffle inside the engine crankcase to help prevent this, if one has an excessive amount of oil passing through, then the rings are worn and should be replaced.