[KD5ITM]

That's funny, the crankcase breather hoes on my Olds 350 goes right up to the air cleaner

[Guaire]

That's funny, the crankcase breather hoes on my Olds 350 goes right up to the air cleaner

  So did the old hose on my GT. We know better.

[ace.cafe]

There is engine vacuum in the air filter housing. Air is pulled out of the crankcase by that engine vacuum, via that PCV hose. The PCV valve in the hose closes if there is any condition that could permit air to go back down that hose into the crankcase.

PCV means Positive Crankcase Ventilation. This means it vents out.

I realize that misconceptions abound about this subject, but I  assure you that I have researched it very thoroughly in scholarly texts and in real world testing. If anyone doubts, truth is clearly found out by doing your own research. I am 100% certain that your independent  research will concur with my statements.

[KD5ITM]

How much crankcase pressure does the 535 build up?

[ace.cafe]

How much crankcase pressure does the 535 build up?

535cc volume change with every stroke.
ThiS is not the only issue however. There is something called pumping losses which occur as the engine tries to pump 535cc of air in and out of that little 10mm hole 1000-5500 times per minute. This is extra work as it acts as an air compressor which uses up horsepower that could have been used to drive the wheel.

If you think it's negligible,  have a look at the vacuum pumps that are standard equipment on virtually every drag race car on the planet. If they are concerned enough about crankcase evacuation on a 1400hp Super Stock car that they install vacuum pumps to reduce crankcase pressure and pumping loss, maybe we might want to think about it on our 20hp RE. We can't afford to lose much, because we don't have much.

[Bilgemaster]

Who has installed a PCV valve on the crankcase where the crankcase breather hose goes into the air box? A long time ago somebody to talk about that on here but I can't find the post. What's the exact purpose of doing that? Is it just to keep oil fumes from getting into the air box causing a slight oily residue on the air filter?

I recently had pretty much the same common breather issues on my old 2005 iron barrel, only a bit more dire (i.e., occasional near-total oil loss). It and the easy fix for "The Heavy Breather Sploodges" are described in this thread, with links to all the necessaries that quickly sorted it out well enough for the leisurely likes of me, along with info on "Ace.Cafe's" far more performance-friendly but difficult mods if you're wanting to wrangle every last pony out of that engine.

[ace.cafe]

The airbox has a vacuum present during running, which draws air from the crankcase most of the time. The PCV prevents air from going back into the crankcase if the vacuum condition isn't present.

The problem with that is that oil has no octane component, and can cause detonation when it is in the combustion chamber.  And oil could be burped into the airbox under certain circumstances,  and oil-soak the filter. So my preference is to avoid venting to the airbox for those reasons.

[Bilgemaster]

The airbox has a vacuum present during running, which draws air from the crankcase most of the time. The PCV prevents air from going back into the crankcase if the vacuum condition isn't present.

The problem with that is that oil has no octane component, and can cause detonation when it is in the combustion chamber.  And oil could be burped into the airbox under certain circumstances,  and oil-soak the filter. So my preference is to avoid venting to the airbox for those reasons.

Not to threadjack here, but I cannot help wondering if that airbox inlet hose for the breather catchcan gizmo, once disconnected and plugged as it is with mine, might not be used as a water injection inlet of some sort. For those unfamiliar with water injection, a fine mist of water is introduced into the fuel-air mixture, which, if done right, increases the octane and power a bit, also cools down the engine, and as a side benefit leaves your combustion chamber squeaky clean. Google is your friend for further details. Suffice it to say that water injection is why your engine will often just seem to run sweeter on a lightly misty morning.

[ace.cafe]

Not to threadjack here, but I cannot help wondering if that airbox inlet hose for the breather catchcan gizmo, once disconnected and plugged as it is with mine, might not be used as a water injection inlet of some sort. For those unfamiliar with water injection, a fine mist of water is introduced into the fuel-air mixture, which, if done right, increases the octane and power a bit, also cools down the engine, and as a side benefit leaves your combustion chamber squeaky clean. Google is your friend for further details. Suffice it to say that water injection is why your engine will often just seem to run sweeter on a lightly misty morning.

The airbox is not a good location for that, but the water injection on the throttle body could work. Probably the best way to do it is set it up like a carburetor  jet with an outboard float levelocity for the water supply.