Msd 8973 ?

Discussion in 'PSI Superchargers Tech Questions' started by pe826, May 21, 2009.

  1. pe826

    pe826 New Member

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    I have a question about the maximum amout of retard that I can run using the 8973 with the Pro Mag 12lt (small 3 3/4 cap). I spoke with MSD and they told me I could safely pull 26deg with the small cap with out crossfire. I wanted to run this by you guys before I ran this set up. I plan on pullin a max of 10-12deg for about 2.5-3 seconds from a 36deg base. This is on a blown alcohol dragboat (jet drive) that needs help leaving the line. Motor is a 540ci, Rfd heads, 11-1 comp., 20ish psi. Any help you guys could provide would be appreciated.

    Thanks
    Jason
     
    #1
    pe826, May 21, 2009
  2. Mike Canter

    Mike Canter Top Dragster
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    This is the way I look at it. Each of the posts on the cap are spaced 45* apart so if you half that you have 22.5* at the mag which is double on the crankshaft. This is the halfway point in the cap. So given the best of conditions you have max of 45* timing change on the crank but there is no way that will happen. If a plug is a little fouled or a sparkplug wire a little high in resistance or a cylinder is a little of on AFR then the spark is going to take the easiest path which maybe to the other post on the cap. So your 12* at the crank is pretty small because it is only 6 degrees at the cap. You need to make sure you are using the wide tip rotor. MSD recommended 26* is only 13* at the cap. I think you are safe.
     
    #2
    Mike Canter, May 21, 2009
  3. pe826

    pe826 New Member

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    Thanks Mike, I hope to try it out soon.
     
    #3
    pe826, May 21, 2009

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