Lots of blowby

Discussion in 'Stage II Tech' started by Alky V6, Jun 1, 2010.

  1. Alky V6

    Alky V6 Let's go racing, boyz!

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    An interesting occurrence over the weekend at the track. Oil started collecting on top of the timing cover. Normal running in the pits, no obvious oil leak.
    The oil only appears after a hard run. It started appearing with the latest increase in boost level.
    It seems to be trailing from the front end seal of the lifter valley cover.
    After some thinking, I figured out that crankcase pressure is building enough to push up on the valley plate and affect the end seal.
    Next PMing of the engine, I'll be increasing the thickness of the valley cover plate and looking into using a different model of rings.

    Those that are building their own intake, pay attention to that possibility.
     
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  2. BlownV6

    BlownV6 Well-Known Member

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    Couple questions!! Do you use a vacuum pump , a dry sump pump , and do you monitor crankcase vacuum?? Any pics of your lifter valley area?? Mike:cool:
     
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  3. Alky V6

    Alky V6 Let's go racing, boyz!

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    I run the std. 4 vane vacuum pump and a three stage drysump pump. There is one typical size breather on each rocker cover feeding into one separation tank. Might need more breathing capacity.
    It's a TA block. It has the opening that it comes with at the front of the lifter valley and a drysump pickup at the rear of the valley. The 4 oil drain backs at each corner of the heads and the pushrod holes. No other drain back holes are drilled in the lifter valley.
    I am not monitoring crankcase vacuum/pressure. I know it's a lot of pressure. It was enough pressure to blow the rear cam plug out on a 1/4 mile pass. I only had one open breather back then.
     
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  4. BlownV6

    BlownV6 Well-Known Member

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    Ok here is what I have found to be the problem in most all cases. You make more boost or get less ring seal and more blow-by is bound to happen. You have a very limited amount of area (drain back holes) for oil to get back to the pan. These are the same holes that the blow by has to use to get to your vacuum pump and and breathers. At some point there may be a short term balance that you can live with as far as how much oil can be trapped in the lifter valley during a pass. Additional oil or additional blow by will affect this ballance and can become a problem even though your only talking about a few seconds. If enough oil gets trapped in the lifter valley then it fills up and becomes a clog in the path of the blowby to reach its exit point. When this happens the crankcase pressure and the oil pressure combine forces in the lifter valley and start some serious pushing forces. Most likely your problem is in the fact that you dont have enough area for the oil to drain back and the crankcase pressure to get out!! Let your little mind churn!! Wont take you long to see what Im talking about!! Mike:cool:
     
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  5. gnxtc2

    gnxtc2 Well-Known Member Staff Member

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    Are you using breathers and a vacuum pump?????

    You must log crankcase vacuum/pressure to find your problem. You could also be un-seating the rings with too much vacuum. And could be starving your pins with oil also.

    I also use a Peterson One-Way valve in case the crankcase get pressurized. http://www.petersonfluidsys.com/engine_breath.html (second one down)

    Billy T.
    gnxtc2@aol.com
     
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  6. Otto J

    Otto J Active Member

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    or you could quite possibly have hurt the motor
     
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  7. Alky V6

    Alky V6 Let's go racing, boyz!

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    I understand.
     
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  8. Alky V6

    Alky V6 Let's go racing, boyz!

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    I use the vacuum pump for crankcase air circulation only. I have always used an open breather (now breathers) to prevent building a vacuum, and allow fresh air to circulate through the engine. Burning methanol fuel, the oil lasts much, much longer with fresh air circulation.
     
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  9. Alky V6

    Alky V6 Let's go racing, boyz!

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    Since the last PMing of this engine in early 2008, I've had a problem with crankcase pressurization. Leakdown tests were good. Plugs clean. Not sure what it could be. I'm leaning towards a problem with the rings under dynamic pressure.
     
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  10. Otto J

    Otto J Active Member

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    total seal rings?
     
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  11. Alky V6

    Alky V6 Let's go racing, boyz!

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    Yep.
     
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  12. Alky V6

    Alky V6 Let's go racing, boyz!

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    Time to build DRW Custom Valve Covers with the killer breather setup! Maybe two piece units.
     
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  13. BlownV6

    BlownV6 Well-Known Member

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    Yep!! You might as well try that!! Im sure that will fix the oil drain back problem:rolleyes: Mike:cool:
     
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  14. turbobitt

    turbobitt Well-Known Member

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    Just a suggestion, since you like to be different, you can build a more efficient breather system like I've seen on some HDD diesiels that work very well. This is how they do it.
    1 - Mount the breather somewhere in the timing cover area.
    2 - Cap the valve covers completly, allowing the whatever pressure to equalize between the level of the breather and the upper end of the engine. This will maximize oil drainback. The lower the breather, the beter.

    I actually seen a HDD diesel engine pump its entire oil pan contents into the valve train area while performing a dyno test with a plexyglass valve cover vented to the atmosphere. The pressure was allowed to take the path of the normal oil drainback. This normally would not occure since the factory VC was not vented and would not allow pressure to vent in this way.

    Allan G.
     
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  15. Alky V6

    Alky V6 Let's go racing, boyz!

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    An absolutely excellent idea. I had toyed with the idea of something on the timing cover. You're description definitely reinforces that idea. Although, with methanol fuel and the amount of water vapor that the blowby contains, I may need to run some manner of breather at the valve covers to keep moisture from collecting. Maybe.

    Or,... just leave the valve covers and breathers as they are and just add a huge breather to the timing cover. I'll at least, add another breather tank to the valve covers. Right now I have both valve cover hoses leading to one separation tank.
     
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  16. BlownV6

    BlownV6 Well-Known Member

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    I agree with this thought process , but to take it a step further , In my opinion the perfect place to place the vacuum pump hose is actually in the oil pan. After all were trying to relieve crankcase pressure and promote oil drain back at the same time!! Relieving pressure from the valve covers really defeats the purpose. Note that I also vent the valve covers to a tank , but I have one of my drysump scavange points at the bottom rear of the lifter valley. Good info here!! Mike:cool:
     
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  17. Alky V6

    Alky V6 Let's go racing, boyz!

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    I still think that, from the viewpoint of keeping the oil clean on an alcohol engine, the fresh airflow needs to travel from one valve cover, through the lifter valley, to the other valve cover. That is where the water vapor wants to hang out. I think the breather off of the timing cover should only present an escape for excess blowby in the event that the crankcase begins to build appreciable positive pressure. Pulling from a low point would not ventilate the top end very well. The hot water and blowby vapors want to rise to the top of the engine.

    I also have a drysump pickup at the rear of the lifter valley.

    I'm going to look into the enhanced vacuum pump. Obviously, someone felt the need to develop a better vacuum pump for some reason. I sure could use a better one.
     
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  18. BlownV6

    BlownV6 Well-Known Member

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    I also had blowby issues until I vented a #16 line from the top/back of each valve cover to a catch tank. As soon as I put this on my oil comtamination dropped probably 50%. I get about 1 shot of clear liquid out of my tank per run. So thats at least that much that did not get mixed up in the oil. Also note that I have a 500 watt heater in my dry sump tank and a 500 watt stick on heater on my pan(new this year) these help to boil the water/methanol out of the oil. I no longer have the need to change my oil every race , mater of fact I basically dont change it for at least 50 runs and only change it then because I feel I should.
    It would be very intresting to know how much of the methanol/blowby is coming from the rings/cylinders and from leakage around the valves!! In my case at 50+ pounds of boost and no valve seals I can imagine it looks like an injector nozzle at the top of the valve guide. Mike:cool:
     
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  19. Otto J

    Otto J Active Member

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    I was TOLD these were not real good for a high heat app.
    Something about heat getting caught between them causing them
    to actually bend up and or down.
    Using a total seal on the second ring was ok in his opinion.
    Being that your on meth, i am not sure your cylinder temps and
    weather this could be an issue or not
     
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  20. BlownV6

    BlownV6 Well-Known Member

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    I went with Dykes style rings on mine , this was recommended by JE for my application and I have nothing but good things to say about them. Mike:cool:
     
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