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Tech Tip cure for pukeing oil onto your header>>>>

Discussion in '1969-1972 K5 Blazer | Truck | Suburban' started by Burt4x4, Sep 1, 2002.

  1. Burt4x4

    Burt4x4 3/4 ton status

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    Driving a 72 K5 accross any desert can be a chalange!
    My old 350 began to puke oil out the pass side right onto the header! Crating a oil cloud accros the hwy. Every 1-1/2hr I had to dump a quart in /forums/images/icons/mad.gif /forums/images/icons/shocked.gif
    So the fix!!!!
    Tori89K5 suggested I add a T to my PCV and put a second one in! So I did! Simply bought a T more hose another PCV & gromet, tossed the stupid breather, and WAAALLLAAAAaaaaaa no more pukeing and now more oil soked K5!!!!!!!!!! /forums/images/icons/grin.gif /forums/images/icons/grin.gif /forums/images/icons/grin.gif
    What a relife!
    Just thought I should share!!!
    Late
     
  2. FRIZZLEFRY

    FRIZZLEFRY 1/2 ton status

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    If we only would have done it a 1000 or so miles sooner /forums/images/icons/grin.gif
     
  3. JIMs70K25

    JIMs70K25 1/2 ton status

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    Was this pukeing because of excessive blow-by? If the engine is pulling air from both valve covers how's air entering the engine? Why wouldn't you just hook one valve cover to the base of the air cleaner and leave the otherside connected to the base of the carb through the PCV valve? Is the pukeing during aceleration only or while cruising?
     
  4. Burt4x4

    Burt4x4 3/4 ton status

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    Possiably?? All I know is adding the second PCV stopped the oil from pissing out of the motor!?
    My air cleaner is an open element so no place for breathers.
    I am talking the wife into a new motor for Xmas (I have to start early) so this workaround is good enough for now. I don't need to find the root cause /forums/images/icons/smile.gif
     
  5. Chris_T

    Chris_T 1/2 ton status

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    Without a breather .. isn't the crank case under constant negative pressure then? Notwithstanding air intake through a potentially air-passable oil cap
     
  6. Sandman

    Sandman 3/4 ton status Author

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    Sounds like he has enough blowbye that its not an issue.
     
  7. Burt4x4

    Burt4x4 3/4 ton status

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    I don't know enough about crank pressure positive or negative???
    So is blowby something that will kill a motor in the long run? What is blowby? Rings?
    I better start working the wife for a new motor!! /forums/images/icons/grin.gif
     
  8. Greg72

    Greg72 "Might As Well..." Staff Member Super Moderator

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    You could always ask Scott to build you a new motor, or rebuild yours...? /forums/images/icons/smile.gif

    As much as I was fed up with my 396 (or whatever it ended up being! /forums/images/icons/tongue.gif ) it was a LOT cheaper to rebuild it with new bearings, seals, gaskets, rings, cam & lifters than buying a NEW crate motor.

    Something else to consider if the WAF (Wife Acceptance Factor) on a brand new engine doesn't work out!!! /forums/images/icons/grin.gif
     
  9. Burt4x4

    Burt4x4 3/4 ton status

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    Hmmmm, good idea! Ya know I have that 350 block too!? Can you say 383....hehehehe
    More $$$ but that is why I work! Right!
    Late
     
  10. Chris_T

    Chris_T 1/2 ton status

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    Yeah .. blowby usually is rings .. forcing combustion gasses past the rings and into the oil/crankcase. I don't know what you get if you have bad valve seals and good rings .. mostly oil sucked past the valves on the intake stroke, but in theory combustion gasses should go past the valve seals too.

    IIRC .. and someone correct me if I'm wrong ... the PCV sucks in air from the crankcase to recycle any unspent gasses by passing them thru the carb and then "re-combusting" them ... this causes negative pressure in the crankcase since you're pulling a vacuum .. to compensate for this you need to replace the air being sucked into the carb from somewhere else and this is done by pulling air thru the breather and into the crankcase.

    If you have a lot of blowby you're throwing oil up into the air and in addition to the PCV you usually foul the valve cover type breathers too .. I know people who run a long hose up to a breather .. anywhere from 4" or more, sometimes with a U or bend to keep the breather filter from fouling as quickly.

    My problem is oil shooting into the PCV, breather and out the oil cap because there are no baffles in my valve covers to keep oil shooting and bouncing off the rocker arms directly onto these parts ... to boot my holes are right over the rocker ams, so there is no room to put a baffle on them, since it often fits between the rocker arms of two adjacent cylinders. I keep meaning to swap my stockers back on, but it isn't a high priority (plus my Blazer sits 1800 miles away right now) .. and besides .. the MT ones look so pretty
     
  11. ZZ4x4

    ZZ4x4 1/2 ton status

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    I had a slightly different take on the PCV vs breather. The PCV hoses from both valve covers connect to the carb and or air cleaner and create a negative pressure (suction) on the crankcase to remove and burn any air/fuel mixture which blew past the piston rings. Because there is not a source of air going into the crankcase, the effect on the carb is like a capped vacuum line which is desirable for proper operation and fuel metering. If there is a source of air into the crankcase (a breather on the other valve cover), the carb essentially has a big leak now through the PCV hose. There really doesn't need to be a draft through the crankcase to remove the gasses. The PCV suction, the pistons going up and down and the blow by from the pistons gives enough molecular motion to be effective. JT
     
  12. wheelin72

    wheelin72 Registered Member

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    How did you mount ur second pcv? Did u just drill a hole and insert a grommet?
    Would this eliminate the need for a baffle?
    I bought summit valve covers with no holes.
    I have the pcv side taken care of but i need to do something for the oil filler side.
     
  13. Burt4x4

    Burt4x4 3/4 ton status

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    That is my same line of thought! Hey it worked thats all I know!

    Wheelin72- My valve covers are Edlelbrock Elite series and they have a hole in each cover with baffels. All I had to do was buy a 3/8 T, more 3/8 line, another PCV valve & gromet. Tossed the breather put the gromet in...well you get the idea! Very easy!
     
  14. ZZ4x4

    ZZ4x4 1/2 ton status

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    Wheelin, Yup like Steve, my covers already had holes for PCVs or breathers on both covers plus baffles. I am not sure you would really need to add a PCV hole to your other cover that has no hole. The oil drain holes in the heads also pass gasses so one pcv may be enough. I'd probably try running with just the one unless you have problems. Of course if you already have holes, you need either a set of PCVs or a set breathers. JT
     
  15. Chris_T

    Chris_T 1/2 ton status

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    True, but there is also a question of 'flow'. Now I know most engines are not air-tight, but you need a source of air flowing 'in' to the crankcase to get a decent flow of air 'out' through the PCV .. otherwise you're just creating a vacuum in the crankcase and you're not sucking in any of the unspent gasses .. they're just building up under vacuum instead of under atmospheric pressure. That's also the reason for the PCV valve .. as engine vacuum drops the little ball falls down so you don't have an open line (well .. not as open, they're not air tight) .. it only sucks gas in when there's sufficient engine vacuum to pull the gas past the check ball. That's when you need some other 'air intake' into the case so that the air can actually flow. If the crankcase has the same amount of negative pressure as the engine is drawing then there will be no net movement of gas .. just diffusion. In theory if the engine had more negative pressure it would pull the air/fuel mix in itself (minus the valve of course). So the breathers are there to allow air 'in' so air can go 'out' and into the carb.

    Of course, most engines that we have probably don't have air-tight oil filler caps, so air can get in, but if it was a completely sealed unit, you'd also be putting negative pressure on all the engine seals, potentially causing a greater chance of pulling water through any seal leaks when the engine got wet.

    Of course an engine with bad blow by will likely never see a negative pressure without the breather, but in a completely sealed crankcase it would be like trying to suck through a straw with your finger plugging the other end .. nothing is going to move no matter how hard you suck.
     
  16. wheelin72

    wheelin72 Registered Member

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    i dont mean to steal your thread burt
    So i would be good with a pcv valve on one side and a oil filler on the other side?
    Would i be alirght without a baffle for a week or so until i can get a baffle made?
     
  17. ZZ4x4

    ZZ4x4 1/2 ton status

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    OK, but the PCV is for emissions, to let the gasses be burned instead of venting to atmosphere. The flow is not important. The diffusion is pretty high. Try putting you hand over the valve cover hole. There is a push pull as pistons cycle.
     
  18. wheelin72

    wheelin72 Registered Member

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    Doesnt the pcv make the engine run better or at least more efficient?
    I dont see how it would rob power.
    Where should the pcv and oil filler be located on the valve cover and on which side of the engine. its a BB chevy
     
  19. Chris_T

    Chris_T 1/2 ton status

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    Fair enough, but I don't agree that there is sufficient diffusion to clear the spent/unspent gasses from the crankcase. If it is a question of power though, why run a PCV at all? Plug the carb and allow the crankcase gases to vent to the atmosphere through some sort of breather valve. I'd have to think I'd fail a visual emissions inspection with two PCV's and no breather just as quick as I'd fail without one. In a worst case scenario, however unlikely, you could end up building up enough unburnt gas in the engine to ignite in the crankcase, no? (If in theory, if not in fact).

    I'd rather not have negative pressure in my crankcase if I could avoid it if I were offroad ... I think I'd even rather be blowing air out then potentially sucking stuff in and I KNOW that my engine isn't buttoned up tight enough that it would hold much of a vacuum anyway .... Hmmmm .... think it would lessen oil leaks? I just may have to try it /forums/images/icons/tongue.gif
     
  20. Steve_Chin

    Steve_Chin 1/2 ton status

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    Another benefit to having a fresh air source for an engine that has a PCV valve hooked up to it is the reduction of varnishing of internal components. Oil drainback out of the heads is usually a little faster with a functioning PCV system (with a fresh air source).

    Also note that at WOT, the PCV functions poorly, which is why the crankcase breather is vented into the air cleaner and the breather tube is usually 5/8" or 3/4".

    Steve, I'd junk your air cleaner can and obtain one that has a bung in the lower pan for the fresh air tube. My hunting buddy just junked his open element air cleaner for a lower can off of an '84 Z/28 305 H.O. (dual-snorkel air cleaner). He's using a lid off of a '70 Suburban that sticks way the heck up over the can, along with a 5" element. It looks funny, but his Blazer picked up a little top end over the old open-element job and it is also quieter.
     

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