Performance 340 total timing

Engine, Trans & Driveline

  1. Moparfeind

    Moparfeind FBBO Gold Member FBBO Gold Member

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    Hey so I have reset my timing to give me better idle but it may have to much advance all in. I was wondering how I could limit my total mechanical timing? All in at 40 degree's seems a bit high especially for Arizona, high compression, iron heads. Larger springs such that I don't get to 40?

    Details:
    • 1973 340 with stock iron heads, auto
    • (unknown cam but very aggressive)
    • Unknown compression >10:1
    • New ignition system > MSD billet dizzy with an 6AL box coil
    • Initial timing 20 degree's (idles much better here than at 15 degrees)
    • All in by 2800 or so at 40 degree's (sounds fine with no load)
    • Pump gas 93 max
     
  2. PurpleBeeper

    PurpleBeeper FBBO Gold Member FBBO Gold Member

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    Yes, you can limit the total mechanical advance pretty easily. Some distributors even have adjustment screws inside that allow you to block the slots to a varying degree (basically, limit how far the mechanical advance arms can swing out completely). If you don't have those screws, they sell some nifty little limiter plates you can put inside the distributor to do the same thing. The plates are marked & have different length "limiting slots" to pick from. I think for a good total advance, you'd want about 36 degrees total & no more than 38 I'd say. So..... (36 degrees) - (degrees initial advance) = (total advance slot to pick with the plate)…...or trial & error if you have the adjustment screws.
     
  3. Moparfeind

    Moparfeind FBBO Gold Member FBBO Gold Member

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    Thanks PB easy enough! I will check out the MSD manual to see what I need! 36-20=16 degrees limit.
     
  4. Moparfeind

    Moparfeind FBBO Gold Member FBBO Gold Member

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    So I found that MSD has an "advance Stop Bushings" kit. They are calling out "Crankshaft Degree's" and have values of #'s 18, 19, 21, 23, 25 and 28. I presume these values are for the amount of mechanical advance. Meaning if I were to choose the #18 and if I set my initial to 20 degrees I would have 20+18 = 38 total degrees. If this is true why don't they make smaller increments like 12, 14, and 16? The 16 is what I need if I wanted to keep my 20 inital where its at.

    Am I looking at this correctly?
     
  5. cryplydog

    cryplydog FBBO Gold Member FBBO Gold Member

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    FBO website has custom bushings.
     
  6. Bill Monk

    Bill Monk FBBO Gold Member FBBO Gold Member

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    • Thanks! Thanks! x 1
    • dvw

      dvw Well-Known Member

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      35 is plenty. Funny story. My son had a 340 Duster years ago. His 1st trip to the track, 35 degrees total. It runs 13.15. I back it up with a 13.16 but think I hear slight spark knock (10.5-1). Pull the timing to 33, 12.88. Pull it to 31, 12.68
      Doug
       
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