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

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.

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!

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 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.