Hemi with hot cylinder (maybe shorter rod?)

Discussion in 'PSI Superchargers Tech Questions' started by FLAT737, Aug 20, 2011.

  1. FLAT737

    FLAT737 Member

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    I have one cylinder that the egt is hotter,port nozzle not changing it much,Has anybody put a shorter rod in one hole if so how much shorter?
    Thanks
    Randy
     
    #1
    FLAT737, Aug 20, 2011
  2. hotrod200

    hotrod200 Member

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    Hi Randy
    I don't have much experience at all but would like to put my two cents worth in to see if someone corrects me if i'm wrong. So please take my opinion with a grain of salt and don't try it unless someone with more experience could confirm what im saying. also please guys don't bite my head off if i'm wrong i'm learning.
    But if you can not correct the cyl temp by adding more fuel to cool it. could you open the valve lash to the intake ? that may reduce your cyl pressure easier than a shorter rod.
    If guys run different length rods, are you re balancing the rotating assembly?
    What would a different heat range plug do in this instance? sorry for jumping on your thread Randy.
     
    #2
    hotrod200, Aug 21, 2011
  3. Mike Canter

    Mike Canter Top Dragster
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    You need to ask why changing the port nozzle jet is not cooling down that cylinder. It should. Maybe the inside of the fuel line going to that nozzle is coming apart and has blocked some of the fuel flow or your nozzle is bad. You should swap fuel line and nozzle with another cylinder and see if the problem changes. Do not change plug heat range because that has nothing to do with it
    The other thing is maybe your egt probe for that cylinder is badly positioned in the exhaust or the probe is bad. You should be able to correct it with a jet size change.
     
    #3
    Mike Canter, Aug 21, 2011
  4. FLAT737

    FLAT737 Member

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    Thanks for the input,I will keep going after the nozzle and replace the hose on that cylinder.
    Randy
     
    #4
    FLAT737, Aug 21, 2011
  5. Mike Canter

    Mike Canter Top Dragster
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    Best is to swap it with another cylinder so you can see the problem switches. Let us know what you find out. Lots of people here to help.
     
    #5
    Mike Canter, Aug 21, 2011
  6. jim phillips

    jim phillips ta/fc

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    what mike said
     
    #6
    jim phillips, Aug 21, 2011
  7. bruce mullins

    bruce mullins Top Dragster

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    before you make changes by what a computer shows, read the spark plug. that will tell you the truth. an overly rich cylinder will show hot on an EGT because it is burning the excess fuel in the header tube. Could be you have gone too far the wrong way. compare the spark plug to one in a different cylinder that you are happy with on the egt.
     
    #7
    bruce mullins, Aug 21, 2011
  8. secondwindracing

    secondwindracing top alcohol

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    back when I worked on a fuel car we used to change rod lengths to help get the car down the track but it seemed to never change the egt. Dave
     
    #8
    secondwindracing, Aug 21, 2011
  9. Mike Canter

    Mike Canter Top Dragster
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    Bruce, just for interest and discussion..... I have heard people talking about an over rich cylinder causing an EGT to read high but I have never seen that happen on any motor that I have looked at or worked on. Don't get me wrong here because I am not saying it can't happen it is just I have never seen it happen first hand. How rich would a cylinder have to get to increase the EGT above all the cylinder EGTs during a run? I would have thought that if a cylinder was that rich then the EGT would drop way down and if way too rich would make the cylinder too wet for the plug to fire.
     
    #9
    Mike Canter, Aug 22, 2011
  10. bruce mullins

    bruce mullins Top Dragster

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    that's a little hard to explain without showing a spark plug. . I have had a cylinder show 1300 degrees and think OH SHIT! but look at the plug and hardly showing heat half way around the plug. on the same run some of the other cylinders show 1100 or 1150 and the plugs are showing heat the whole way around the plug.
     
    #10
    bruce mullins, Aug 22, 2011
  11. Kendrick Roberts

    Kendrick Roberts Member

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    Hot EGT/ cold plug

    I have seen the same thing as Bruce has, and I have seen the opposite. A very hot plug with cold EGT on the same motor. After playing with it a little, I decided to believe the plug rather than the EGT. I had assumed that it was a combination compression/timing issue and thought that a different length rod might be a solution, or as hotrod suggested, playing with valve lash to alter cam timing and the resulting dynamic compression. I think that the rich cylinder with high EGT comes from a slow burn or retarded timing on that cylinder, maybe the intake is closing a little later dropping the dynamic compression a little, or one of the other hundred things that make it all work is different. I would like to know that myself.
    Bottom line is (for me) the spark plug has more authority than the EGT.
     
    #11
    Kendrick Roberts, Aug 22, 2011
  12. Mike Canter

    Mike Canter Top Dragster
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    Don't get me wrong...I believe in the plug reading over the EGT probe. I just never have a had a cylinder so rich it has raised the EGT temp and have it cool down when I lean it out.
     
    #12
    Mike Canter, Aug 22, 2011
  13. TADHemiracer

    TADHemiracer Member

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    That would be a new one on me too.
     
    #13
    TADHemiracer, Aug 22, 2011
  14. clarky

    clarky New Member

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    I have had a few engines where i have changed rod length to help even out nozzling, cant help you with the egt, however on a 4.456 bore hemi 10th rod change usually equalled around a 3th nozzle change to bring the egt's/plugs back into line.

    Clarky
     
    #14
    clarky, Aug 23, 2011

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