Port Check?

Discussion in 'Manton Push Rods Top Alcohol Tech Questions' started by BEDNAR1320, Sep 4, 2017.

  1. BEDNAR1320

    BEDNAR1320 Member

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    I was checking my port check setting and noticed that it will leak very slight, starting about 5# before it actually cracks/opens. This is an adjustable check with the threaded adjuster inside, not the shim type. I took it apart to make sure the poppet and seat looked OK and don't see an issue. Any ideas? Should I replace it with the shim type? I have a shim type at the idle check and it doesn't do that, just opens cleanly without leakage before it opens.
     
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  2. Mike Canter

    Mike Canter Top Dragster

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    I would replace it with a shim type. If yours leaks you could run rich at idle. The normal is 20 lbs or look at your fuel pressure at idle and make sure it is above that.
     
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  3. Will Hanna

    Will Hanna We put the 'inside' in Top Alcohol
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    I have done several customers with roots fuel systems from Randy Anderson with port checks set to 8 lbs (8 intake nozzles). It could very well be the spring has went a little weak. I agree 5 is low but I wouldn't just bump it to 20 lbs unless you had documentation it was originally set up that way.

    Also unless you are measuring fuel pressure behind the barrel valve, pressure at the pump at idle will be different than what the port check see's.
     
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  4. Mike Canter

    Mike Canter Top Dragster

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    All you care about is not having it open at idle so 20 lbs works just fine. As soon as the motor rpm comes up at launch it is going to immediately go above 20 lbs and open the poppet.
     
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  5. Bob Alberty Jr.

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    Hey Brian,
    I run a pump, and nozzle pressure transducer on my deal. Will is correct that their is a pressure difference. My laptop isn't in front of me, so memory says my number was 24lbs at the check.
    Being a trans brake, 2 step deal, put it on the chip, download the data and where yo go from there is up to you. Mine makes 24lbs at the check, so thats where the check is set. Then we control average egt during the 2 step dwell with the converter helper. She's crisp and clean at the release. This is with a 15.6 pump, your results may vary. :)
     
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  6. Will Hanna

    Will Hanna We put the 'inside' in Top Alcohol
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    All I'm saying is if you start from scratch with 20, have everything around it, whatever, that's your tune up. I just don't like the idea of jumping from 5-8 to 20. I have a 481x deal with a roots I am tuning and I have to keep the port check pretty low to keep the rear cylinders cool.

    Obviously a 20 lb check will flow less than a 5-8 lb check.

    There are many different theories and set ups to a fuel system. I just caution anyone from making that big of a jump. It may be fine to make that jump. Then again, like my 481x car, it may have hot cylinders in the back that depend on that low check to keep the egt's down at idle. If the nozzling is based on the egt being 'x' at idle, if you raise that a couple hundred degrees, could be trouble down track.
     
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  7. Mike Canter

    Mike Canter Top Dragster

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    Will, if you read the original post he never said what it was meant to be set at. He said it started to leak at 5 lbs. surely if it was set at 5 lbs it would be open at idle and the motor would be real rich
     
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    Last edited: Sep 6, 2017
  8. max

    max New Member

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    Take a line off, drop it in a clear bottle and stage test.
     
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  9. BEDNAR1320

    BEDNAR1320 Member

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    Sorry guys, been offline for a few days.

    To clarify, the check was set at 26#, but would start leaking slightly at 20-21#

    I have just changed to a shim style and it cracks open cleanly without leaking first.
     
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