SBC timing
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Thread: SBC timing

  1. #1
    Burn out champ 2010 Dusty's Avatar
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    SBC timing

    355ci SBC with rumpy cam of some sort and roller rockers (standard ratio).

    I timed it up the old school way...close enough to run and then moved the dizzy about for fastest idle.

    I then put the timing light on it aiming for 8* BTDC at idle and around 34* at 3000 rpm but it was nowhere near my first setting.

    Setting to the timing light needs the idle stop screw moving in a fairish way to get the idle up to speed.

    Which is the best way to set the timing?...and don't say rolling road.

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    Official RnS Addict Zody's Avatar
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    Re: SBC timing

    Quote Originally Posted by Dusty View Post
    355ci SBC with rumpy cam of some sort and roller rockers (standard ratio).

    I timed it up the old school way...close enough to run and then moved the dizzy about for fastest idle.

    I then put the timing light on it aiming for 8* BTDC at idle and around 34* at 3000 rpm but it was nowhere near my first setting.

    Setting to the timing light needs the idle stop screw moving in a fairish way to get the idle up to speed.

    Which is the best way to set the timing?...and don't say rolling road.
    With a rumpy cam 8* deg sounds abit low ? my old 355ci ran lovely at 13* deg fitted with a edelbrock RPM cam..
    The car is open, the keys are under the dog !

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    Re: SBC timing

    depending on cam specs,, you will probably need a lot more initial advance ,, i run a large ish roller and my initial is 18 degree.. i would advise you to try to advance the idle timing a few degrees.. total timing of 36-38 degrees is good

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    Burn out champ 2010 Dusty's Avatar
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    Re: SBC timing

    Thanks chaps...I'll have a look at it in the morning.

    A mate told me to use a separate battery to power the light as it can pick up random signals from the car electrics....I do this as I have a spare battery but is this a myth?

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    I'm Not Jed Clampett stueeee's Avatar
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    Re: SBC timing

    Quote Originally Posted by Dusty View Post
    A mate told me to use a separate battery to power the light as it can pick up random signals from the car electrics....I do this as I have a spare battery but is this a myth?
    A myth IMO. your 12V battery should suppres any electrical noise as in electrronic terms the battery acts as a giant smoothing capacitor wired across the low voltage connection for your timing light. You do need to be carefull of noise with the plug lead inductive pickup on the timing light though; make sure it isn't close to any other lead other than the one you're hooked up to.

    Re. earlier posts on what to time to, I just time my modded SBC for 36°/38° with the centrifugal advance all in at 3000+ revs and let the tickover advance setting look after itself.


    Last edited by stueeee; 26-04-2010 at 10:51. Reason: jumbled words!
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    Official RnS Addict WB54's Avatar
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    Re: SBC timing

    You've lost engine vac at idle from the lumpy cams duration /overlap.

    Bump your initial timing or recurve the dizzy to match the cam and drill a 0.8mm hole in each primary throttle blade. Keep going up in 0.2mm increments till you get it idling at 800rpm, then bring it up to 1000rpm with mixture screws, will idle perfectly.

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    Re: SBC timing

    if you have an msd ignition system, dont use a dial back light to set timing, use a regular nonadjustable light

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