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what should i set timing at???

Discussion in 'The Garage' started by bigbadchev84, Apr 11, 2005.

  1. bigbadchev84

    bigbadchev84 1/2 ton status

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    i have a stock 76' 350 in my 84 blazer, it has an aluminum intake, 1inch carb spacer and a 600cfm edelbrock electric choke carb with a 6inch k&n filter and stock exaust manifolds into 2inch duals into 3inch flowmasters and tail pipes, sm465/208 and 4.10 rear axle now while i am installing my detroit and seals etc. in my 4.56 14boltff. i am running 39.5 boggers and this thing is a dog right now, this is a newly installed motor i picked up, i have no idea how many miles are on it, but this thing is a dog, as soon as i put it in 4th gear it falls flat on its face, i have to cruise around in 3rd all the time to get the thing moving. what should the timing be set at? it is currently at 6degrees.
     
  2. Mad-Dog

    Mad-Dog 1/2 ton status

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    you can play with the timing but i doubt that is the problem, carb spacers increase plenum volume and are primarily used for top-end improvements, topping things off is the emissions (electric choke) calibrated Edelbog 600 that is probably jetted mucho lean for your motor (the carb spacer is just aggravating the problem), lose the spacer, recalibrate the carb for non-emissions and try it again
     
  3. bigbadchev84

    bigbadchev84 1/2 ton status

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    i just replaced my worn out quadra-jet with this carb today, it seems to do a little better, i now have the same setup that is on my brothers goodwrech motor, except he is running 35s on his truck and it does great, i know that mine is a worn out motor, but the fuel delivery is identical. i know im not leaning the motor out i can slightly smell that it is just a little rich, but not bad.
     
  4. MTMike

    MTMike 1/2 ton status

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    Factory spec for static advance at idle on my old '79 w/ a stock 350 was 8 degrees.

    You might wanna bump it up to 8-10 (back it off if it pings) and see if that helps at all.
     
  5. rcamacho

    rcamacho 1/2 ton status

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    Total timing - then curve

    Get a timing tape or dial back light to set the total centrifugal advance to 32-36 degrees. 32 is generally safer. Make sure that the vacum advance is disconnected during this procedure. Whatever the initial timing is after getting to 32 is what you need for optimal WOT power. After that, get a set of advance springs/weights to play with the curve. Dial in a moderate to slow curve if you are conservative, else read the plugs for potential detonation.

    On to vacum advance-
    Get an adjustable can and dial in about 10-12 degrees total.

    This is a quick overview, search the web there are a lot of great articles out there. If your truck is having issues @ cruise than it's probably lack of vacum advance (slow or ruptured can) or jets. I ran a Carter 625 on my BBC and the mixture was so lean it would stumble very badly and barely accelerate. Since swapping to a Holley 750 it's terrifying to step on the throttle :laugh:
     
  6. trailblazer86

    trailblazer86 1/2 ton status

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    The carb spacer will aid your engine at high revs and hurt down low.
    Check out the Revs for your truck.
    With no overdrive at 50mph your engine is only revving about 1700 - 1800 rpm.
    4.88 gears will get you close to 2100 rpm. Still below or near the stock range.
    Most Stock cams work fairly well in this range.
    The spacer does not help this out at all.
    I tried the same set up with my adaptabrock carb. It is now sitting up high on a shelf, replaced by Quadrajet.
    The small primaries help it get away at the lights.
    Trucks are heavy, tall tires only amplify the weight problem. Check out this chart and it may better explain what I am trying to say.

    www.4lo.com/calc/geartable.htm
     
  7. highrider_44s

    highrider_44s 1/2 ton status

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    before i'd do this i'd try and get a compression tester and test the crancking compression of your motor. Disconect the power to you distributer then take all the plugs out and jam the carb at wot then crank the motor over with the tester in each cylinder. all the cylinders should be roughly within 10 psi of each other.

    If you get a low reading (110-150)you can set the curv to come in faster and i'd go to 36* all in around 2500-3000 rpm

    if you get a high reading (150-190) then set the curve so it comes in slower all in 3000- 3500 and be more carful with going to 36* total you can still go to 36 but if you bring it in too early it will ping and thats not good :D
     

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