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Thread: F134 Crankcase Breathing?

  1. #1

    F134 Crankcase Breathing?

    Hey guys, Ill take any opinions or suggestions here. So getting to final rebuild stages on this F134, 54 Wagon and trying to decide on PCV/Ventilation setup. Here is what I have planned and tell me if it should be enough.
    Note: I wont be driving in any real dusty conditions

    1. Removing the down draft tube and close that hole off on the lower exhaust valve cover.
    2. My intake valve cover already has the vent tube with PCV running to intake at carb, will leave that. Someone may have updated the cover over the years?
    3. Oil dipstick has the small vent tube and have I a small K&N filter there for ventilation
    4. I dont have the oil bath parts, so plan on installing the K&N filter alternative at the horn on the carb

    My only concern was since the design of this engine with the exhaust valves lower in the engine, would there be an issue not having a vent at that specific location?

  2. #2
    Super Moderator bmorgil's Avatar
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    The setup is the same regardless of where the valves are. The pressure in the crankcase is leakage from the rings mostly. Anything that gets past the valve guides will also add pressure to the crankcase. The PCV system is a controlled small vacuum leak, with a one way valve (the PCV). Flow is from fresh air to the vacuum source. You need to draw clean air from the air filter, or through a separate filter into the crankcase. Your K&N at the dipstick will do fine. Most of the time you simply pick up the air from the main air filter. The small vacuum leak causes a slightly leaner condition under less than full load. The carb should be adjusted slightly richer in the idle and the intermediate circuits, if it was originally from a non PCV system. Under heavy load there is no vacuum and consequently, the full load jetting wont be affected. With those things in place, and the road tube plugged, the PCV hooked to vacuum under the carb will function as designed. When the rings are real bad, a road tube is the only thing that keeps pressure out of the crankcase.

    I use the PCV often on street driven high performance vehicles. The constant pull of fresh clean air into the crankcase, helps to keep the oil clean and free of carbon. Some racing engines run a few variations of crankcase vacuuming to actually pull vacuum in the crankcase. There is a benefit to ring seal especially at high RPM, when you achieve some vacuum in the crankcase.
    Last edited by bmorgil; 06-16-2024 at 07:36 AM.

  3. #3
    Thanks for that breakdown and explanation! Sounds like my plan should be okay? To be clear, I will have K&N filters at carb and oil dipstick vent tube as I have seen others with. I had to plug that oil dipstick tube off or put a filter since no oil bath system currently. I have seen those run the pcv from the exhaust valve location, so was just wondering if okay to just close that one off now since I have one from the intake port at carb running to intake valve cover.
    Sounds like one ventilation system is enough?

  4. #4
    Super Moderator bmorgil's Avatar
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    Yes one is enough. The vent at the dipstick is the original crankcase intake air location. A hose ran from there to the air cleaner.

  5. #5
    So would I benefit any by routing the dipstick hose to the air cleaner? It would take some modifications for sure.

  6. #6
    Super Moderator gmwillys's Avatar
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    Not really. Long story short, our 2A doesn't have the cross over air tube for the air cleaner because the head studs are too short to mount the cross over tube. The dip stick breather nipple is capped off with a rubber cap. As long as your PCV is in good shape, the breather works just fine. With the dip stick out there is very little to no pressure noticed at the dip stick. The only time I might have an issue is if there is a massive amount of blow by, but in the Heeps former life, it had a hole burnt through a piston, and it consumed a whole lot of oil, and the blow by was immense. It had the cap on the dipstick then too. The PCV was clogged up then, but still ran alright considering.

  7. #7
    Super Moderator bmorgil's Avatar
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    Routing the intake air for the PCV to the air cleaner closes up the system so to speak. On high performance and "off-road" stuff, a separate setup like the one you have is more common. You must make sure you eliminate positive crankcase pressure in any engine with pistons as much as possible. Positive crankcase pressure gives the rings a tough time sealing. The closed PCV system made sure that even when the rings and valve guides were shot, all that blow by stayed in the engine and was consumed in combustion... somewhat. The PCV was the very earliest of "Pollution Control Devices".

  8. #8
    Thanks! So more things to think about here. sounds like your saying it would be better to route from the dipstick to the air cleaner or close it off completely? I could mod the air cleaner to accept a hose from there but would take some work for sure.

  9. #9
    Super Moderator bmorgil's Avatar
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    No do not close it off completely, you need clean intake air. The setup you have is fine. It is used in off road vehicles all the time. I have a few motors set up that way. Your small dipstick filter will clean the intake air to the crankcase as the PCV draws it through.

  10. #10
    I see, so let me ask this, would it make a better system overall if I routed dipstick hose to air cleaner? I can do it if needed and thanks for your help on this!

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