Please help need advice!!!

Discussion in 'General Questions' started by Andres, Oct 2, 2016.

  1. Andres

    Andres New Member

    So I am very concerned about port matching the GT80 cylinder with my stock crank transfer ports.My concern is I am running stock cdi and a 6cc high compression head.Do you think it will start if it does will it run without a problem.Do you recomend I upgrade to this cdi below??? gt80-engine-only-720_78b64022-7b2a-41a8-a526-2480dc58d5a8_large.jpg 4138_large_e9bb40f2-b3cb-41a5-a26c-94810ed46f94_large.jpg
     

  2. crassius

    crassius Well-Known Member

    it is stroke and rod length that will need to be matched - ignition timing won't change
     
  3. jaguar

    jaguar Well-Known Member

    any good engine builder will tell you that when you increase the compression you need to retard the ignition.
    The Lightning is more retarded than standard but not as much as the Jaguar CDI.
    These engines need a 7.5cc head. Anything less gives too much compression which will cause the cylinder plating to flake off and the bearings to have a short life.
     
    Timbone likes this.
  4. Andres

    Andres New Member

    W
    Were can I by a jaguar cdi and a 7.5cc head
     
  5. jaguar

    jaguar Well-Known Member

    Click on my signature link to go to my site and go to the CDI page.
    I don't think anyone makes a 7.5cc head which is one reason I stay mad at all of the parts suppliers.
    If anyone knows of one then please inform us.
    If there is none then you can sandpaper down the stock head about .8mm or buy a 7cc head and dremel out more space in the combustion bowl. Either way you'll need a pressure gauge to make sure you don't exceed 130psi.
     
  6. Andres

    Andres New Member

    Thanks
     
  7. gary55

    gary55 Active Member

    These heads do not increase compression unless replacing a stock straight plug head. Left to right stock straight plug head = 10.1cc, stock slant plug head = 6cc, pancake performance head = 7.9cc, rounded fin performance head = 8cc, flat fin performance head = 8cc. The head on the far right is the head sent with the GT 80 engines. I am not real smart on the various performance gains achieved through the differing chamber designs. I can tell you that the gains are not due to increased compression. The slant plug head has the highest compression of all the heads below.
    [​IMG]
     
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