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is the oil filler / breather 289 full flow in the center better than being on the valve covers?

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  • #31
    Originally posted by bensherb View Post

    Mike, the non"R" engines don't have that vent stack from the oil pan. With that stack going into the intake air path you have a positive flow vent system, and the breather caps shouldn't have any back flow. The standard engines do not have a positive flow system. At low RPM you are correct, the breather caps let air into the crankcase to replace air removed by the PCV. At high RPM and low vacuum there is more pressure being developed in the crankcase and no vacuum to evacuate it via the PCV, some of that pressure will be vented through the breather caps.
    As for your smoker, if you pulled that much oil into the intake you'd have problems with it running, so another crankcase evacuation system could be used. A scavange system, which is totally different than these and dumps into the exhaust to be burnt there on its way out. But the EPA might get miffed.
    I recall the scavange system you describe in the 1070s-80s. Those cars actually had a belt driven, "air pump" to scavenge the vapors and pipe them to the exhaust, as you describe. If the pump ever froze (fairly common) nothing would change if you simply removed the belt. At least that was common practice back in the day. I bought new AMC Concords in 1978 and 1982, and they both came with scavenge pumps.

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    • #32
      There are a variety of crankcase ventilation systems, with the draft tube system vapor pressure is created by blow-by and this can vary greatly from engine to engine. At very low speeds the draft tube may be ineffective and consequently the developed vapors will take the path of lesser resistance and migrate up through the filler cap. At higher speeds where the draft tube is most effective may scavenge greater velocity than that is produced by the engines blow-by and the filler cap will replace the require air. The filler caps work in both directions. It would not be desirable to operate an engine with a vacuum created in the crankcase.
      A PCV system could not operate effectively if the system is "sealed" if a PCV system becomes overwhelmed with crankcase vapor there needs to be means to evacuate the excess vapor. On some designs there may be breather caps with limited flow ie the two small holes in the cap or a solid cap that redirects excess vapor via a rubber hose back up through the air filter housing and back into the engine. This component would only be activated where the vapor is in excess of that what the PCV valve can accommodate. This would not be operating all of the time. Today in modern engines no vapor is allowed to vent to atmosphere and the excess vapor created where the PCV valve is overwhelmed is directed in to a charcoal cannister and then is purged at regular intervals directing the vapor back into the engine. On some modern motorcycle engines there is no "breather" type inlet, the vapor pressure is only created by blow-by and is directed into an oil, water and vapor separator, where as the oil and water are separated from the vapor and the vapor is redirected back through engine and the unwanted water and oil is collected in a tube and controlled drained at regular intervals, nothing goes to atmosphere. With the technology of the day there was no issue with venting unwanted vapors to atmosphere. Even with the early PCV systems some vapor could still vent to atmosphere this was inherent in the design. Some early designs redirected the vapor directly into the exhaust manifold however this method was short lived, and soon after the cannister system was introduced that controlled all vapor from being directed to atmosphere.
      With Air Care and other smog control inspections systems cars of the day were not required to up grade as the regulations are not retroactive. The tests were to attain the best possible values as there were no standards for older vehicles. The engine had to be in the best condition attainable.
      The Air Care standards here in BC were taken from the California standards, they have since been discontinued. The PCV system was designed out of necessity, millions of cars operated with a draft tube for nearly 60 years with no engine operating issues. There was a military tank that had five Dodge flat head engines for power all equipped with draft tubes. The engine compartment was regularly contaminated with oil vapor as there was no practical way to evacuate the unwanted vapor. The engineers designed a system to redirect the unwanted vapor into the air filter housing and this temporarily solved the problem, however the air filters became prematurely contaminated. A modified design redirected the unwanted vapor into the base of the carburetor and again this was short lived as there was a vacuum created in the crankcase and if in the event of a backfire a catastrophic explosion would occur dislodging the breather caps and dip sticks. A redesign was introduced and a check ball was installed in the line to prevent the migration of explosive vapors reentering the crankcase. This design became to be known as the PCV system. This system has been tweaked over the years but basically is the same as the original design which was developed out of necessity only. If you had an early Ford, Dodge or Chev and you intended to sell it and the vent tube was exhausting visible vapor it was customary to redirect the vent tube via a rubber hose in to the air cleaner and this would solve the problem of the smoking engine, what a bargain.

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      • #33
        Great dissertation I THINK (don't know)!
        With only Two Paragraphs and no sentence breaks, no line breaks, pretty much unreadable.
        StudeRich
        Second Generation Stude Driver,
        Proud '54 Starliner Owner

        Comment


        • #34
          Originally posted by altair View Post
          There are a variety of crankcase ventilation systems, with the draft tube system vapor pressure is created by blow-by and this can vary greatly from engine to engine.

          At very low speeds the draft tube may be ineffective and consequently the developed vapors will take the path of lesser resistance and migrate up through the filler cap. At higher speeds where the draft tube is most effective may scavenge greater velocity than that is produced by the engines blow-by and the filler cap will replace the require air.


          The filler caps work in both directions. It would not be desirable to operate an engine with a vacuum created in the crankcase.
          A PCV system could not operate effectively if the system is "sealed" if a PCV system becomes overwhelmed with crankcase vapor there needs to be means to evacuate the excess vapor.


          On some designs there may be breather caps with limited flow ie the two small holes in the cap or a solid cap that redirects excess vapor via a rubber hose back up through the air filter housing and back into the engine. This component would only be activated where the vapor is in excess of that what the PCV valve can accommodate.


          This would not be operating all of the time. Today in modern engines no vapor is allowed to vent to atmosphere and the excess vapor created where the PCV valve is overwhelmed is directed in to a charcoal cannister and then is purged at regular intervals directing the vapor back into the engine.



          On some modern motorcycle engines there is no "breather" type inlet, the vapor pressure is only created by blow-by and is directed into an oil, water and vapor separator, where as the oil and water are separated from the vapor and the vapor is redirected back through engine and the unwanted water and oil is collected in a tube and controlled drained at regular intervals, nothing goes to atmosphere.


          With the technology of the day there was no issue with venting unwanted vapors to atmosphere. Even with the early PCV systems some vapor could still vent to atmosphere this was inherent in the design. Some early designs redirected the vapor directly into the exhaust manifold however this method was short lived, and soon after the cannister system was introduced that controlled all vapor from being directed to atmosphere.


          With Air Care and other smog control inspections systems cars of the day were not required to up grade as the regulations are not retroactive. The tests were to attain the best possible values as there were no standards for older vehicles. The engine had to be in the best condition attainable.


          The Air Care standards here in BC were taken from the California standards, they have since been discontinued. The PCV system was designed out of necessity, millions of cars operated with a draft tube for nearly 60 years with no engine operating issues. There was a military tank that had five Dodge flat head engines for power all equipped with draft tubes.


          The engine compartment was regularly contaminated with oil vapor as there was no practical way to evacuate the unwanted vapor. The engineers designed a system to redirect the unwanted vapor into the air filter housing and this temporarily solved the problem, however the air filters became prematurely contaminated.

          A modified design redirected the unwanted vapor into the base of the carburetor and again this was short lived as there was a vacuum created in the crankcase and if in the event of a backfire a catastrophic explosion would occur dislodging the breather caps and dip sticks.

          A redesign was introduced and a check ball was installed in the line to prevent the migration of explosive vapors reentering the crankcase. This design became to be known as the PCV system. This system has been tweaked over the years but basically is the same as the original design which was developed out of necessity only.

          If you had an early Ford, Dodge or Chev and you intended to sell it and the vent tube was exhausting visible vapor it was customary to redirect the vent tube via a rubber hose in to the air cleaner and this would solve the problem of the smoking engine, what a bargain.
          how's that

          Comment


          • #35
            I will try to simplify this and make it less wordy. Every engine creates some crankcase pressure
            created by blow-by. There are two basic methods of controlling said vapors. Draft tubes were
            designed to exhaust the unwanted vapors and because of certain conditions where the draft tubes
            were undesirable, the vapors were re-directed back through the carburetor intake.

            This new design became known as a Positive Crankcase Ventilation System. Either of the systems performed the same function-----to remove and or control the unwanted vapors.

            With the draft tube system at higher speeds the tube may extract more vapor than is created in the crankcase and to avoid a vacuum condition air is let in via the filler cap "breather".

            At the other end of the function, at lower speeds the vapors will vent back up through the filler cap.
            With an early PCV system the function identical, in lieu of the vapors being vented to atmosphere they are re-directed back in to the combustion chamber.

            With a less than perfect engine if the vapors created are greater than the PCV system can accommodate ie. at lower speeds, the excess vapor will migrate back up the filler tube and at the high speed end the vapor removal system (PCV) system may remove greater than is produced and therefore the filler cap "breather" will let in the require air to avoid a vacuum condition.

            Both system work exactly the same and remove unwanted crankcase vapors. Some systems are configured differently however the function is the same there is no great mystery.

            Crankcase vapor removal systems using the PCV system must all be compatible relative to the type of carburetor used with the object to avoid creating a vacuum. There is considerable more design with a PCV system than with a draft tube.

            Where it isn't in contravention with the law I remain a proponent of the draft tube, I am opposed to re-directing contaminated vapor back into the engine. All of the components of both systems require regular maintenance to function as designed.

            Neglect can be very costly and prematurely destroy an engine --- voice of experience.

            I am not opposed to a mature discussion on the subject and the reason for the comprehensive report on the subject is because there is considerable misunderstanding of the issues. This subject resurfaces from time to time and the same issues continue to be re-discussed without resolution.

            I would gladly discuss any of the issues that you may have, but to simply just criticize the report offers no resolution.

            Before the Air Care was discontinued in this area there were tune up shops nearly every square block living of the avails of the failed Air Care vehicles and usually because of one or two parts per million of exhaust gases. The government set a maximum that the shop could charge $300 and every job was $300 regardless of the fault.

            If any modifications were done to the vehicle the cost was doubled to $600. With out a passed certificate you could not drive the car and in many cases it had to be scrapped.

            My point to all this is do the required maintenance and avoid the consequences.


            Comment


            • #36
              Originally posted by JoeHall View Post

              I recall the scavange system you describe in the 1070s-80s. Those cars actually had a belt driven, "air pump" to scavenge the vapors and pipe them to the exhaust, as you describe. If the pump ever froze (fairly common) nothing would change if you simply removed the belt. At least that was common practice back in the day. I bought new AMC Concords in 1978 and 1982, and they both came with scavenge pumps.
              Just like my Mercury GM 1987.

              Comment

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