barrel valve leakdown

Discussion in 'PSI Superchargers Tech Questions' started by Andy Bowman Jr., Oct 21, 2006.

  1. Andy Bowman Jr.

    Andy Bowman Jr. New Member

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    Hi guys thanks for the GREAT site it really helps.I am VERY new to blown alcohol and need some help.I run a SBC and from everything I have read here my barrel valve is to rich (merky oil,breaking up,fuel in puke tank).I have checked everything else and in the process of checking barrel valve.I am using snap-on duel guage leakdown tester,have done everthing according to enderle instructions guage reads 48%(should be 65% been told)when adjust hex rod to lean as instructed (clockwise) it lowers %.am I reading guage backwards ,I believe this guage reads actual % leaking.Any help would be great. thanks
     
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  2. Mike Canter

    Mike Canter Top Dragster
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    Lets hope I remember this correctly. You want it to read the percent down from being wide open. If it is a leakdown tester and you are putting in 100 psi on the left gauge then 0% would be nothing going through so in fact 85 on a leakdown gauge is 85% leakdown.

    You have to block off the idle return line and you need to take off the fuel outlet hose to read correctly.

    The first thing you want to check is the V groove on the barrel in the barrel valve is positioned at the inlet side or is it on the outlet side of the valve. You can actually look into the inlet with a flashlight and see it. It needs to be on the outlet side. If you have the leakdown tester hooked up and you slowly open the throttle then the leakdown should go up to 100% at WOT. If it goes down whe you first open the throttle then it is in backwards.

    Yes I would say that 48% is a little rich. We run our motor at 83%. At lot depends on the idle return poppet setting. You need to check that with the leakdown tester also and see if that is where you think it should be. We run ours at 9 lbs.
     
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  3. OzAlky

    OzAlky Member

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    What type of blower are you using ?
    With a late model PSI, you would be in the 65% range.
    If you are too rich at idle by a lot, the engine will generally start to hunt... i.e. revs will go up and down.
    You will have fuel in the oil, etc if the main is way rich too. It may not be the barrel valve.

    You might want to check the calibration on your leak down tester - not sure, but I think they should read 100% through an 85 jet ? Can anyone confirm that ?

    Hope that helps.
     
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  4. Andy Bowman Jr.

    Andy Bowman Jr. New Member

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    It is a roots 871.The engine is loping.The fuel sytem was originally set up by reichert,but I have killed the overdrive to save parts and just have fun.Due to shrinking budget i'm trying to figue this out myself.It probably is a few things but i'm trying to elliminate one at a time.Thank you guys for replying this site and your help is great.
     
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  5. OzAlky

    OzAlky Member

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    Aussie to American translation... hunting = loping :)

    Sounds like it's rich - BUT ... it might lope anyway if you don't have much weight on the back of the crank i.e. if you're running a converter.
    If you lean it until the idle becomes fairly steady, you'll be close. If the idle starts going higher, and the engine starts to smooth out -you're too lean. (sorry, that might be confusing. It needs to still have that chunky, deep idle without loping).
    After that, you will adjust the b/v to maintain the engine temp you need at the start line - get a CHT gauge if you haven't got one.
    You'll quickly learn what leak down you need for the engine to be at the right temp to leave best.
    When the air is bad, you might need to take a couple of % leak out, and vice versa when it's good.
    Good Luck with it.
     
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    Last edited: Oct 22, 2006
  6. Matt

    Matt Member

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    The easy way to get started is make sure the small slot cut into the spline of the spool is at the top basically straight up this will give you around 75% leak adjust the butterflies 6 to 8 thou and start motor, with an auto you want the motor to run smooth at 1800 rpm in 1st gear with the brake holding the rear tyres from moving. if you are using the alcohol barrel valve make sure it doesn't have a 32 stamped into the splined end of the spool this is for injected only. If the motor is lopey open the butterfly gap 1thou at a time make sure to wind the scroll back so that the slot is straight up again. With what you are doing 75% should be fine, it is hard to know because timing, comp, overdrive, fuel pump and tune up all play a part in the overall running of the motor.
    good luck.
     
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  7. OUTLAW

    OUTLAW New Member

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    I went through the EXACT same thing with my hemi just a few weeks ago! I borrowed a Mac dual gauge leakdown tester, set the barrel valve at 90% on the second gauge (100 on 1st) The motor would not run when I took the bottle away. Finally figured out that the 2nd gauge actually needed to be at 10! BIG DIFFERENCE! This was actually 90% leakage. This time it was obviously VERY rich, moved the second gauge to 15 (85%) and all is well. Should still be fat but I can tweak it. If you get the second gauge above 30 you'll notice the motor heats up really quick at idle. Also, once you get the leakage set verify that the arm on the hat and the arm on the barrel valve are at the same angle so they will open at the same rate.
     
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