Timing a SBC?
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Thread: Timing a SBC?

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    Compulsive chicken choker English Impala's Avatar
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    Timing a SBC?

    A bit wierd this.... Trying to get the Chevy running properly. Its always been way too rich & very sluggish. If you floor it quickly from standstill it back fires through the carburettor.

    First step was to set the timing properly using a strobe. I painted the grooved timing point on the harmonic balancer white (with a piece of black insulation tape either side of it so it is easily detected), hooked the strobe up to No.1 plug and...... it doesn't pick up the white timing mark! No matter how far I move the distributor its as though the timing mark is in the wrong place.

    Any ideas? This ones got me completely stumped.

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    Dragging not Bragging vince-305's Avatar
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    Had a simular problem Gary and got the boys around to help but for starters id guess you have an aftermaket dress up kit as thses timing tabs seem to be off alot and harmonic balancers have a tendency to spin the outer rim

    Id start by removing no1 pulg and inset a thin screwdriver and rotate engine by hand you will notice the piston pushing the screwdriver up at the tip and when it gets to the top of its travel thatll be top dead center then you can mark the damper or at least check the postion of timing tab and damper then go from there

    (remeber that the piston will rise and drop twice for a full rotation so dont get it 180 out now and the screwdriver if inserted to far can jam the enging so becarful and its a pain as it does slip out so its better with help)

    Good luck
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    Off the Xmas card list kapri's Avatar
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    Oh have I been here with this one Various pulleys with differing timing marks and , I'm told, different positions or keyway depending on what year of Chevy, coupled with eth ability for teh harmonic balancer to shift on the pulley

    Simplest way is as Vince has said back to basics and check that the marks are in the correct place, just cos the pulley came with the engine doesn't mean i'ts the correct one, been there before as well.

    Is it the original dizzy or aftermarket ?

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    I'm a grown up drunk! chevy2's Avatar
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    First off, does the timing light flash? i assume it does,
    some timing lights dont wanna play ball with certain msd units,

    if so you need to determine where the white mark relates to when no1 cylinder is at TDC,
    take out no1 spark plug, manually rotate the engine until the piston reaches the top, check with a screwdriver,
    you should now be able to see the white mark in relation to your timing tab on your timing cover,
    if its nowhere near it may be a truck motor which has the tab in a different position, regular sbc's have the tab a about 2oclock looking from the front,
    truck motors are at 12oclock,
    assuming you've found TDC mark on your damper,
    make sure when timing your motor remove the vacuum advance pipe as this will give a wrong reading,
    depending what light you're using shoot for around 12-14 degrees before TDC at idle and around 34-36 degrees on a stock s/block,
    basically you first need to find where the TDC mark on the damper relates to first.

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    Compulsive chicken choker English Impala's Avatar
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    I suspected the pulley may be in the same "quality" league as all the other engine bits I've bought..... "Bolt on & go"? Never!

    Carb is an aftermarket HEI set up. The problem I have is trying to turn the engine over by had as the compression is very good & access to the pulleys is limited so I'll try removing the plugs to help & find TDC with a screwdriver.

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    Compulsive chicken choker English Impala's Avatar
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    Quote Originally Posted by chevy2 View Post
    First off, does the timing light flash? i assume it does,
    some timing lights dont wanna play ball with certain msd units,
    Yes, it flashes.

    if its nowhere near it may be a truck motor which has the tab in a different position, regular sbc's have the tab a about 2oclock looking from the front,
    truck motors are at 12oclock,
    Good point. The engine is a mid 90's Vortec unit from a truck, that would explain the problem.

    Thanks for the pointers folks, its given me a starting point! The cars been MoT'd for a week now I want to be using the damned thing!

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    I'm a grown up drunk! chevy2's Avatar
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    one other thing, run the motor up, turn the dizzy anti-clockwise, if the idle goes up thats a sign its too retarded,
    a lot of tuning problems are resolved with the correct timing,
    even a well tuned motor will fall flat on its face when you nail it if you pull too much timing out,
    get the timing right first before even thinking of touching the carb.

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    Stroker Kustom Jim's Avatar
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    Is there not that old chestnut re: putting dizzy back in one click out!?

    Taken from classiccarauto.com
    First, this document assumes you have not removed the distributor from the engine. If you have, you will need to bring the engine to TDC or "Top Dead Center" in the firing position for the number one cylinder, then reinstall the distributor so that the striker on the distributor rotor is in the 6:30 position, detailed later in this document. There is a trick to this, but that is another document altogether.


    I'm quite nervous about installing mine

  11. #9
    I'm a grown up drunk! chevy2's Avatar
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    Quote Originally Posted by Kustom Jim View Post
    Is there not that old chestnut re: putting dizzy back in one click out!?

    Taken from classiccarauto.com
    First, this document assumes you have not removed the distributor from the engine. If you have, you will need to bring the engine to TDC or "Top Dead Center" in the firing position for the number one cylinder, then reinstall the distributor so that the striker on the distributor rotor is in the 6:30 position, detailed later in this document. There is a trick to this, but that is another document altogether.


    I'm quite nervous about installing mine
    It doesn't really matter if you install your dizzy 1-2 or 3 splines clock or anti-clockwise,
    what matters is that no 1 lead on the cap wherever you choose to put it relates to where the rotor arm is at TDC and the firing order is correct and the correct rotation,
    for example; if at TDC, you install your dizzy so that the rotor is at 6pm, put no1 plug lead on the cap at 6pm and rest of the leads as normal,
    or say, at TDC install the dizzy with the rotor at 12pm, fit no1 plug lead on the cap at 12pm and the other leads as normal,
    does this make sense?

  12. #10
    Rods 'n' Sods Junkie 440+6's Avatar
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    On top of all the other ideas & not wishing to insult your intelligence, you are checking No. 1 cyl arn''t you & not No.2 ? only it is not universal which front cyl. is No. 1 between manufacturers.
    Martin '63 Fairlane Sports coupe (v. long term project)
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