Tuning Help

Discussion in 'PSI Superchargers Tech Questions' started by Milanmetal, Nov 9, 2015.

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  1. Milanmetal

    Milanmetal Member

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    first let me start off by saying this is my first blown alky motor so please bear with me.

    My engine starts and idles great until the engine starts to warm up. So it will set there and run perfect for 5min plus with no problem what so ever. After these few minutes are up the idle wants to start cracking and you can hear something has changed. I thought it was starting to lean out so I opened my turn buckle....no change. So went the other way and leaned it out...no change.

    Right now I am .007 on my butterflies and somewhere around 70-75% on my leak down. I am not sure where to go from here so ANY help or ideas would be greatly appreciated!

    The engines specs:

    557 ford
    14-71 HH Littlefield (1:1 - roughly 10lbs of boost)
    Buzzard catcher
    110 pump
    BT heads
    11:1 CR
    .620ish flat tapped cam

    This is a monster truck application.
     
    #1
    Milanmetal, Nov 9, 2015
  2. kosky racing

    kosky racing Comp Eliminator

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    Put some preasure on the idle check
     
    #2
    kosky racing, Nov 10, 2015
  3. wld4x4

    wld4x4 Member

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    How big is the vent on your fuel tank? Might be trying to suck the tank in. Try it with the cap off!
     
    #3
    wld4x4, Nov 10, 2015
  4. Milanmetal

    Milanmetal Member

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    I have a #8 vent and rollover vent.
     
    #4
    Milanmetal, Nov 10, 2015
  5. youngtuner

    youngtuner Member

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    Get a chance give me a call
    see if i can help 978.423.5881
    Never satisfied Blown satisfaction tuner
     
    #5
    youngtuner, Nov 10, 2015
  6. Milanmetal

    Milanmetal Member

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    Thanks!

    I will shoot you a call tomorrow.
     
    #6
    Milanmetal, Nov 10, 2015
  7. BEDNAR1320

    BEDNAR1320 Member

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    X2, you need to check the pressure the idle check opens at. I have mine at 30#
     
    #7
    BEDNAR1320, Nov 10, 2015
  8. Mike Canter

    Mike Canter Top Dragster
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    i think an idle check poppet for a Roots blower car needs to be at 10 lbs with a .010-.012 air gap on the blades and a leakdown of 82-84% with the idle return blocked off and the out line of the BV disconnected. The setting of the idle return poppet pressure and the leakdown percent go together. The higher the poppet setting the lower the percentage leakdown. You can make any setting work but the normal setting is 10 lbs it has to be within the range of your idle fuel pressure. After you have it all set then with your hand snap the throttle off of idle and if it hesitates then adjust the rod for more fuel if it blubbery then lean it out. You want a nice crisp off idle response. Once you get that the check your leakdown percent and record it so you can always return to that point. Just as a note, I seriously doubt that most people have 30 lbs of fuel pressure at idle so in that case all the fuel is going to go into the motor at idle and nothing returned. This would make the idle super rich. You could just cap off the return.
     
    #8
    Mike Canter, Nov 10, 2015
    moparbob498 likes this.
  9. BEDNAR1320

    BEDNAR1320 Member

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    Interesting Mike, with this new fuel system first time out, the idle check was at 2# and I had a serious bog (a 500 rpm dip for .75 sec.) just after converter flash. Yet the idle and response was good. To cure to bog, I set the idle check to 30# (only other spring I had) and turned the rod to get the same idle speed and response as it was with the check at 2#. The throttle response is good and the bog was gone. IIRC the leak with the 2# check was 80% with the check it's at 50%. I have right at 30# FP at idle. 135 pill. EGT's and plugs look very close. Four blade hat at .008, aerated hat nozzles. 1600 idle RPM in gear, no surging at all.

    All that being said I only have a 9.2gpm pump, but I only run 16# boost.

    Maybe I'll bring the check back to 10-20# range and set the leak to 70-75%

    This is a HH14-71 on a 565 BBC
     
    #9
    BEDNAR1320, Nov 10, 2015
  10. Bob69

    Bob69 Member

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    Make sure your barrel valve spool isn't rotated to far and fuel is going thru on the backside of the spool.
    Disconnect BV in and out hoses.
    Hold a small flashlight from the rear of the BV and look thru from the front.
    You should only see light coming thru the "V".
    Have fun.
    p
     
    #10
    Bob69, Nov 10, 2015
  11. Milanmetal

    Milanmetal Member

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    When I am setting my leak down % I have been blocking both returns and leaving my hat and port lines open. Is this the correct way? I have a K valve if that matters.

    When I put my butterflies at .010 it seems to idle too fast. I will try it again tomorrow and see how it all goes.
     
    #11
    Milanmetal, Nov 10, 2015
  12. Mike Canter

    Mike Canter Top Dragster
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    That is the way I do a leakdown.
     
    #12
    Mike Canter, Nov 11, 2015
  13. Will Hanna

    Will Hanna We put the 'inside' in Top Alcohol
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    First thought is make sure the venting of the tank isn't doing something stupid after the fuel level goes down to the 5 minute mark. Overly rich would be a problem right away; it should burn the fuel easier as it gets heat. Too lean should have shown response to richening the bv. I'm assuming it doesn't get better if you clear the motor out. I don't know what kind of ignition you have, but maybe something is getting hot? The blower is not getting overly hot is it?

    Again first guess is something with the fuel tank vent and fuel level. Make sure you have a reinforced line to the inlet of the pump and it's not trying to suck the inlet line shut.
     
    #13
    Will Hanna, Nov 11, 2015
  14. Dave Koehler

    Dave Koehler Member

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    Milan Metal.
    Idles too fast. What is too fast?
     
    #14
    Dave Koehler, Nov 11, 2015
  15. Milanmetal

    Milanmetal Member

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    Thanks for the replies guys!

    Today I put the butterflies at .010 and my leak down around 83 which did help a little. I think my throttle was holding them open a bit the last time I did put them there. I am idling about 15-1600 rpm which I believe is fine.

    I think Will is correct and I am WAY rich. 6 of the 8 plugs look like total garbage. I changed them and went up to a 140 main to see what that will do. I ran it for a bit today and I am hoping to check the plugs again tomorrow .
     
    #15
    Milanmetal, Nov 11, 2015
  16. Mike Canter

    Mike Canter Top Dragster
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    your main jet does not control your idle mixture.
     
    #16
    Mike Canter, Nov 12, 2015
  17. Will Hanna

    Will Hanna We put the 'inside' in Top Alcohol
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    A few observations-

    If you are dead rich, there usually is no doubt. It would be huffing fuel out of the pipes at idle, sound like crap as soon as you fired it up. What I meant was that if you were dead rich, if it ran for 5 minutes it should idle cleaner with some heat instead of starting to have problems. If it was loading up from idling rich too long I would suspect you would see the problem well before the 5 minute mark.

    As Mike said, main jet adjustment will have little to do with your idle. You adjust idle with bv and idle check adjustment.

    Hard to tell much from plugs at idle. Unless you are running a ton of prelube, plugs should look new after just idling.

    What kind of head temp or water temp are you seeing after 5 minutes of idling?
     
    #17
    Will Hanna, Nov 12, 2015
  18. Milanmetal

    Milanmetal Member

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    It must be in this idle check adjustment. I have tried everything else except that. I will call Good Vibes tomorrow and get a few springs. Which ones do you guys recommend?
     
    #18
    Milanmetal, Nov 12, 2015
  19. TADHemiracer

    TADHemiracer Member

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    10 pounds
     
    #19
    TADHemiracer, Nov 13, 2015
  20. Dave Koehler

    Dave Koehler Member

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    A couple of things
    1: Your idle is too low. You are not "up on the pump".
    2: There is no load at idle so it will appear sloppy and the plugs will show no heat..
    3: IF it takes more than a flat to change the idle characteristics you do not have enough idle check valve spring pressure. Increase spring pressure. Conversely this can be too touchy for some, then reduce pressure.
    Ok, that was 3.
     
    #20
    Dave Koehler, Nov 13, 2015
    moparbob498 likes this.
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