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Open or Closed Breathers?

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Old Sep 2, 2011 | 01:26 PM
  #21  
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Originally Posted by tekvette
Thank you. The line comes off the driver valve cover, loops around the back of the motor to the T fitting u see in front of pass side hood latch. Then the pass side valve cover loops under the pass fender to the T as well and then to the breather.
The solenoid thing with the guage is the Deadhead regulator for the carb.
got it. thanks. and that flip valve on the bottom of the breather is for draining? with all the shiny black in the photo it was hard to see exactly the circuit, that looks great. bob
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Old Sep 2, 2011 | 09:28 PM
  #22  
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yes thats the drain. thx again Bob.
The fittings on the valve covers btw are push in -12 fittings. If anyone is interested I can post a link of where I found them. With the correct grommet, it's a real tight seal.
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Old Sep 3, 2011 | 11:36 AM
  #23  
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I'm looking at this setup and the biggest problem I see is your only venting excess crankcase pressure. I see no way that your able to evacuate, or "flush" the harmful crankcase combustion by-products out.

You need a cross flow through the crankcase with filtered fresh air entering one bank, traveling through the entire crankcase, and pulling or flushing the harmful compounds out the oppisite side. This is generally done with the intake manifold vacuum on a street build, or either header collector evac systems on open header track cars....or the best solution is a belt driven vacuum pump pulling from one bank with a vacuum releif valve on the opposite side (you dont want to pull over 14-15 " vac or you start to pull off the wrist pins and crank journals).

Understand, this is one of the most misunderstood systems on any engine....stock to full out race.

Here is some related reading:

Understanding PCV Systems


To understand why we need a proper PCV system one must understand what takes place in the crankcase during the average day of driving. First off, all internal combustion engines have a certain amount of "blow-by" or leakage past the piston rings into the crankcase. This consists of several compounds such as unburnt fuel and a small amount of the combustion gasses that result from the explosion of the air/fuel mixture. The combustion gasses contain several nasty things including sulfuric acid, carbon particles, and other caustic compounds that will contaminate the oil over time. In the crankcase there is also a certain amount of water, or moisture from condensation. Even if never run, an engine will accumulate moisture from the heat of the day to the coolness of the evening depending on how humid the climate is where the motor lives. Every time the motor gets run up to operating temperature these compounds are "gassed off" and with the OEM system it all gets "flushed" or pulled into the intake manifold where it is mixed with the intake air charge and burned in the combustion process and further in the catalytic converter before it is exhausted into the air as mostly just water vapor at that time. Now of course, a small amount keeps leaking past the rings into the crankcase and completes the cycle all over again, but without a proper vacuum pulled ventilation system....these nasty compounds will break down the oil and reduce its protection properties and the corrosive aspects start to rust internal parts resulting in reduced engine life.
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In the "old days" of our grandfathers, the engineers that designed engines new the importance of evacuating these nasty compounds and the design was extremely simple. First was nothing more than plain breathers to allow excess crankcase pressure to be released or vented. But the damage from not "flushing" all the gasses out resulted in very short engine life (of course the oils of that day were nothing like the protection today's synthetics provide) so the next change added a vent tube, or evacuation tube that ran from the top of the crankcase to low on the car where the air streaming past would create a suction, or vacuum that would pull the vapors out and vent them directly into the air with a breather (barely filtered with a wire mesh type media that was oiled to catch dust & dirt) allowing the "fresh" makeup air in to complete the flushing process. Now this resulted in greatly increased engine life, but as the motors got worn oil would start to drip out the tube and drip onto the roadways, then the rain would wash it into the ditches, where it would enter the ground water (you know the rest of the EPA story) and the gasses just vented to the air.
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As the EPA and the powers that be mandated stricter emission laws the system was refined more and more ultimately evolving into what we have today. A completely sealed system that uses the vacuum provided by the intake manifold to draw these vapors out, and the filtered fresh makeup air is drawn from the main air intake system and filtered by the main air filter. This results in very clean emissions, but the unintended issues are the detonation or "knock" that occurs when oil is introduced into the combustion chamber that the knock sensors pick up (before we*can hear it)*and pull timing to protect the engine from damage, and thus reduced power. Another result is the carbon buildup on the valves & piston tops (any techs reading this can surely verify the amount) also resulting in decreased performance and less power made.
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The purpose of a proper oil separating catch can is to route these gasses through a baffle system that provides the most contact possible with the outer surface resulting in the oil being trapped and removed from the other gasses that do continue on through the intake and are burnt and consumed. It does NOTHING else in ANY way to the engine oil itself....it can't.
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Deleting your PCV system:

While this will insure NO oil the the intake tract via the PCV, it will greatly shorten the life of your engine if street driven. The worst example I have seen is to cap off all the fittings and run an open hose from each valve cover to near the ground. One would think “they are both releasing pressure, so what can it hurt”. The answer is plenty. Lets take the basic principle of the Venturi effect. Whip a piece of hose around in a circle so that air rushes past the end. This will result in suction from the end of the hose near the center of the radius. Now with a car traveling down the road at speed, both hose will have air traveling past the ends and one ultimately will have more air rushing past thus creating more suction, and the other will them become a vacuum tube sucking up dust, dirt, water, sand, etc. directly into the engine from the side with the least suction. Depending on the amount of dust & dirt on the roads you travel (just look under your hood to see all the sand & dust that accumulates on the engine exterior). So it may take years to destroy your engine this way, or it may take no time at all. To see this if you have been misguided into doing this just remove each valve cover, and looking up into the baffle in each you will see the accumulated dirt built up as it comes in contact with the oil.

Now, addressing the "Home Depot" oil separator, it will and does catch a small amount of the oil but the majority still gets past into the intake (we used these and then the other cans that popped up on the market through the years before designing the ultimate final product that is offered today) and the reasons are simple:
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It is plastic and transfers heat very inefficiently so very little condensing takes place.
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The size. Anything less than 1 qt capacity and there is not enough surface area to be as functional, and the volume needs to be enough to allow the flow to slow enough for the oil to drop out of suspension.
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And the lack of an effective baffle system allow oil to be pulled directly through.
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As for having steel wool or another type of filter media inside, this will work well at first to trap oil....but as soon as it gets saturated droplets are pulled off and into the intake.
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Why don't the auto manufacturers incorporate something similar? Cost and the added maintenance was deemed something that would NOT be accepted by the general market. (even though it is as simple as draining the can at each oil change).
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Bottom line is this: The OEM system does a great job of meeting emission standards and removing the harmful contaminants, but the unintended consequences are the oil that is drawn into the intake charge. For an engine to produce the maximum amount of energy per explosion (of the A/F in the combustion chamber) you want air & fuel only....any amount of oil in this mix will hamper the explosion resulting in less energy released, detonation, and carbon buildup. Trapping and removing this oil before it gets into the combustion chamber is the ONLY solution to maintaining the maximum efficiency and prevent excess carbon buildup.
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Old Sep 4, 2011 | 09:47 AM
  #24  
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Ahhhhhhh that is good reading, thank you for posting.
So, I know I do not want to introduce oil back into the intake because this motor will see a fair amount of track time and I want a clean combustion mix.
So let me ask, what if I simply ran an additional line from that catch can breather to a passenger side header primary? That would create a fair amount of vacuum during part throttle driving I think.
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Old Sep 4, 2011 | 11:19 AM
  #25  
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Originally Posted by 7T1vette
If you are racing the car, the engine is producing a LOT more engine fumes internally than it would do as a street engine. The PCV valve you are using (if 'stock' for your engine) is likely not large enough to handle the excess, nor is the feeder hose or nipple on the carb base. If you don't use the power brake vacuum connection at the rear of the carb base, you might want to try running a larger PVC hose to that fitting and see if it helps. Also install a PVC valve that is made for the largest displacement engine you can find (6-7 liter displacement); it might have enough capacity for your needs.
there is a cheap effective solution, use the check valve for a power brake booster. it handled my L-88 very nicely years ago.
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Old Sep 4, 2011 | 01:25 PM
  #26  
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Originally Posted by tekvette
Ahhhhhhh that is good reading, thank you for posting.
So, I know I do not want to introduce oil back into the intake because this motor will see a fair amount of track time and I want a clean combustion mix.
So let me ask, what if I simply ran an additional line from that catch can breather to a passenger side header primary? That would create a fair amount of vacuum during part throttle driving I think.
As long as you have no mufflers on at all (any muffler will cause a reversion pulse that will keep blowing the header evac flow valves) that would be a great addition.



Originally Posted by 7t9l82
there is a cheap effective solution, use the check valve for a power brake booster. it handled my L-88 very nicely years ago.
Yes, that is an effective checkvalve to use but you still need to have a constant suction/pull to keep evacuating the harmfull compounds completely from the crankcase. You want a good cross sectional flushing flow through the entire crankcase.

The best solution on a race application is a belt driven vacuum pump pulling from one valve cover and a vac relief valve in the opposite one.

The vac pump then dumps into a breathered 1 qt or larger liqyid/fluid catchcan that you empty after every run/session. You will see a ton of water pulled as well as the rest of the harmful combustion byproducts.
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