Poor Fuel/Air Distribution At Idle

Discussion in 'Manton Push Rods Top Alcohol Tech Questions' started by BEDNAR1320, Jan 24, 2017.

  1. BEDNAR1320

    BEDNAR1320 Member

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    On my 540 12° BBC with a HH 14-71 I'm having trouble with keeping # 1 and 2 from going very fat at idle especially #2. If I lean the BV enough to keep #2 lit at idle number 7 and 8 are right at or a little over 1000° at idle.

    I've checked to make sure the ports aren't adding fuel at idle. I've also tried going with smaller nozzles in the front of the blower, that didn't make any difference, the blower screws everything to the front anyways, but thought I'd try.

    Going down track the EGT's are within 100° front to back and the plugs look happy.

    The blower is not setback, but it does have the rotors setback in the case. The front edge of the pie shaped discharge opening is even with the center of cylinder #2 intake port.

    I can live with this, but my concern is the high EGT's in the rear cylinders at idle, as soon as the throttle goes wide open the EGT's start to even out and get within 100° of each other pretty quickly. I wouldn't think it's going to hurt anything, but interested in opinions.

    Thanks in advance.
     
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  2. Mike Canter

    Mike Canter Top Dragster

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    About the easiest way to fix that is to add a second nozzle to each of the front cylinders getting fuel from the hat distribution block and use a very small port jet and subtract that area from the size of the regular port nozzles jets. Used to be real common to do that.
     
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  3. TADHemiracer

    TADHemiracer Member

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    I guess I missed something but it seems to me that if the front cylinders are drowning at idle already that simply adding a second nozzle to those cylinders would make the problem worse. Shouldn't the second nozzle be in the BACK two cylinders to help the lean condition? OR how about not even give a rats patootie about the idle temps. Who launches at idles anyways?
     
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  4. Mike Canter

    Mike Canter Top Dragster

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    Sorry, yes switch the two extra nozzles to the back cylinders
     
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  5. BEDNAR1320

    BEDNAR1320 Member

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    Interesting. I did reduce the hat nozzle average and move that fuel to the ports in an attempt to help-it didn't.

    I might try that Mike. That would allow me to lean the BV a little more to clean up the front cylinders some more at idle. Thanks!
     
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  6. Bjs344

    Bjs344 Member

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    I have often idled at well over 800 on a couple cylinders. If it idles long enough, these will hit low 900s. I was Tuliping stainless exhaust valves a lot but it was rarely the ones that idled hot. Point being, I'm skeptical that there are any ill effects of a couple cylinders idling hot as long as you're not actually overheating the motor. I will say, I can't stand to see 1000 at idle and so have turned the barrel valve a couple times when this happened.

    What is your area split top to bottom (actual area not corrected for boost)?
     
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  7. BEDNAR1320

    BEDNAR1320 Member

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    52% hat 48% ports. I have Ti valves so it should be OK.
     
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