Initial Timing Advance Question

Discussion in 'Engine Topic' started by Brads GN, Jul 22, 2012.

  1. Brads GN

    Brads GN Veteran Member

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    Could you guys give me a ballpark figure on what initial advance you guys have used for the Comp Cams Magnum 280H cam...and the RPM you set it at. TIA.
     
  2. Pfrederiksen

    Pfrederiksen Veteran Member

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    I usually shoot for 34-38 deg all in and let the initial fall where it may.
    (probly 18....ish)
    Although your combo will dictate.

    P
     
  3. CorkyE

    CorkyE Veteran Member Lifetime Gold Member

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    That real dependent on your distributor. Most aftermarket units will have something like 22* mechanical so 14 initial will get you to 36 total. If it's a smog era dizzy, that's a different story...
     
  4. Rene Melten

    Rene Melten Veteran Member Lifetime Gold Member

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    I've got mine at 20 btdc, 35 at 3000 rpm. Idles at 750 rpm. My vacuum is just under 10 in hg.
     
  5. REARSPROCKET

    REARSPROCKET Veteran Member

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    Total advance timing number can depend on the head's combustion chamber, older irons like a higher number like 38-40* and newer vortec styled chambers like 32-36*.
     
  6. EricsZ28

    EricsZ28 Veteran Member Lifetime Gold Member

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    As already alluded to, you need to tell us which distributor you have and if you have vacuum advance connected or not. It would also be good to know how much mechanical advance your distributor has. If you don't know, you really should figure this out. All of these factors, as well as your combo, will influence the answer.

    While that is not a huge cam, it is still big enough to respond to vacuum advance at idle (or more initial without vacuum advance - depending on your combo).

    As rearsprocket said, I ran my old Comp 280H at closer to 40° total timing, with 22° mechanical advance, 18° initial, and old iron heads on my lower compression 400 sbc.
     
  7. Brads GN

    Brads GN Veteran Member

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    It's the original factory distributor.
     
  8. EricsZ28

    EricsZ28 Veteran Member Lifetime Gold Member

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    Have you changed the springs in that HEI yet? My '80's HEI didn't fully advance until after 4k RPM's (very lazy). I would suggest getting a spring kit and putting in a light and medium spring. Then, set your total timing to 36 degrees. See how it runs.

    If you are feeling bold, look into limiting the mechanical advance so you can run 18 initial, and 18 mechanical. I bet it would run even better.
     
  9. Hoot

    Hoot Veteran Member

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    my 454 with 292h cam 18initial, 20 mechanical, 15 vacuum. will idle at 600 but I idle it up around 900-1000 so when the electric fans kick on and the alternator kicks in, it will drop to around 700 :)
     
  10. gingerbreadman

    gingerbreadman Veteran Member

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    Not the same cam but somewhat comparable.... 18 initial, 18 mechanical.Idles at 700 no vacuum advance.
     

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