Crankcase oil catch can: fact or fiction?

I have some experience with the engineering behind crankcase ventilation, but it was with Diesel engines, so...

1). Cars do not have catch cans because of the maintenance required. You gave to empty them out periodically.  Also, the amount of oil consumed is minuscule for daily driven cars. Race cars at full throttle and cars with worn out rings may produce more oil, so a catch can MAY be useful. However, I suspect that in most cases you will never notice a difference. The supposed advantages include less oil deposits in the intake and valves and combustion chamber, less oil consumption (if you dump the catch can back into the crankcase), and longer catalytic converter life.  It takes thousands of miles to make a difference, so I'm not sure they are actually worth it.

2). Route it into the intake. There are two reasons OEMs do this. The first is for emissions so that the blow-by gases do not escape. A second reason is that it regulates crankcase pressure. The piston rings require a certain pressure differential to work properly. If the crankcase is over pressurized, oil consumption will increase, kinda defeating the purpose.  Do not vent to the exhaust. That will definitely cause over pressurization, unless you properly design for a Venturi effect. Routing to the intake is fine, the amount of blow-by is small compared to the air normally going into the engine.

The Civics of that vintage don't have a straight vent to the air cleaner.  That bulge on the air cleaner is meant to separate oil from the blow by gases.  Check that all the gaskets in there are intact and the separation chambers are clean - that might stop some of the oil consumption.

Yea, stock air cleaners have the little catch thing that includes a vacuum line from the manifold itself to provide negative pressure all the time.   Keep meaning to see if I can rig up something similar.  We haven't had any specific crankcase pressure issues like weeping main seals.

Nice advice, richv70 (and others)...thanks....I am off to Lowes for all the car parts I need for the installation....

Just a FYI, a mason jar is a really bad idea. It could do is job well but it's glass. Consider it breaking when say someone else's hooptie crashes into yours and dumpins 10oz of oil on your hot exhaust. Bad bad news. Glass has no place holding flammable liquids in a race car (fuel filters, oil catch, etc.) Imho.

This is what we use, though admittedly it is a bit oversized. The 16oz size didn't look big enough.

http://www.rei.com/product/852355/rei-n … e-32-fl-oz

We use an aluminum water bottle.... which is handy because you can mount it in this for easy empty/service: