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confused and frustrated with timing problem...

Discussion in 'The Garage' started by cheyennesuper, Nov 7, 2004.

  1. cheyennesuper

    cheyennesuper Registered Member

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    I'm having a couple problems with my '73 k5.First is the timing or something...Its a 350 with a holly.They say the timing should be at 12@600 but its backfiring out the the carb at that.Pretend the indicator thing with the numbers went up to about 24,thats about how far i had to advance it to get it to run right as far as i can hear.Now it just hesitates alot.Someone told me my distributer could have been installed wrong or the carb is way out of adustment...Does anyone have any ideas? The other thing is my speedometer.When i spin the back of the instrument the needle bounces so i assume thats fine.I know the speedo gear is spinning cuz i jammed a stick in the end with a string tied to it and it wraps around the stick when i drove it.I hooked the cable up and the instrument still shows nothing.Can anyone please help?Thanks.
     
  2. 79Stomper

    79Stomper 1/2 ton status Premium Member GMOTM Winner

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    Not sure if your 73 is the same as my 79 but had similar problems when I put the new motor in. My distributor had a vacuum advance on it and I had to modify it to work with my motor set up. I believe in total timing I was some 40 some odd degrees off of TDC and then I had to adjust the carb. Mine would sit and idle fine but whenever I would put it in gear and start taking off it would spit and sputter and back fire like all get out. Not sure if it helped but this was just my 2 cents.


    James
     
  3. m j

    m j 1/2 ton status

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    plug the vacuum advance
    ensure you are hooked to #1 plug lead
    is the pointer a match for the damper?
    you can test that with a piston stop
    start at the basics and work through it
     
  4. rcamacho

    rcamacho 1/2 ton status

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    First of all, check total mechanical timing in addition to iniital advance. Use a balance tape or dial back timing to verify 32-36 total timing with the vacum advance disconnected. If you are over or under, adjust your initial advance to bring the numbers in line. Most Chev V8's can tolerate up to 12-16 degrees initial timing. After that, verify that your vaccum advance is working and plugged into a ported, not manifold vaccum source. You will probably want to limit vaccum advance to 10-15 degrees total. 40-50 degrees total (mech+vaccum) is about right. 50 may be excessive for a high comp engine, while a 8.5 CR smogger may be able to handle it.

    After that's all straight, then start on the carb tuning.
     
  5. cheyennesuper

    cheyennesuper Registered Member

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    Thankyou Thankyou Thankyou...If it wasn't so damn late i'd go do all that right now.I'm pretty sure its the vaccume advance.
     
  6. mechted

    mechted 1 ton status Premium Member

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    your speedo cable may be broken ( or stripped out)
    if you can get the guage end of the cable to where you can see it during driving (easist way is probably to remove the whole cluster) watch to see if it is turning when you're moving

    it might also be stripped - the ends may be plastic and sometimes they break... they should be square, if not that is likely the problem
     
  7. diesel4me

    diesel4me 1 ton status Premium Member

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    Also check the mechanical advance weights--they sometimes rust and stick in the advanced position,or the pins the weights ride on get grooved and make it advance eratically.They have advance curve kits you can buy that have plastic bushings that go over the worn pins,and come with new weights and an assortment of new springs to adjust the advance curve to new specs. /forums/images/graemlins/crazy.gif
     

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