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Thread: 385sbc timing question

  1. #1
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    385sbc timing question

    i've got a 385sbc its all forged with eagle bottom end dart heads lunati voo doo cam installed straight up.the top end consists of an edelbrock air gap intake 770 street avenger carb and msd hei billet distributor. my question is this when i go to time the car it doesnt want to idle under about50 degrees and when i do back the timing down to around 34-36 (with the vacumm advance unhooked) it starts to run poorly and backfires through the carb wehn you hit the throttle.any ideas on what it could be.the motor has a aftermarket fluid balancer and cloyes timing chain cover with aftermarket pointer.think the timing marks could be off? could i be one terminal too far clockwise on the distributor cap with my #1 plug wire?is there any easy way to double check to make sure the timing marks on the balancer are right?
    thanks for any help!!!!!

  2. #2
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    Verify TDC on the Balancer and timing tab are actually located at TDC first.

  3. #3
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    i took the valve cover off and made sure that both valves were closed on number one cylinder when the timing tab and harmonic balancer registered zero.i dont think thats a real accurate way to tell tough is it?is there any other way to do a more accurate job on locating exact tdc?

  4. #4
    Senior Member MASTER BUILDER
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    It is a little more in depth. I recommend removal of all spark plugs for making it easier to turn over by hand. But, you have to take out #1 spark plug and create a stop of some sort, just so the engine will not rotate completely. I have used a Philips screwdriver before stuck through the spark plug hole. This must remain at the same location and depth for both marks. Do not use the starter. Gently rotate clockwise by hand until it stops against your stop. Now make a mark on the balancer at the pointer. You can place masking tape on the balancer and mark on this instead. Next, you must rotate it counter clockwise until it stops against your stop. This will be almost 1 complete revolution. Now, you will make an additional mark on the balancer. TDC is the point halfway between the two marks. Verify that this lines up with the machined mark on the balancer. Remove your stop before doing anything else, so that you don't forget.

    Bill M

  5. #5
    Administrator RACING JUNKIE bjuice's Avatar
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    without taking off the head and placing a dial indicator on it with a degree wheel... ..this is the only way to get close other than what Bill said above.
    continue as you did by taking off valve cover and getting both valves closed...check your piston in #1 spark plug hole and make sure the piston is up..its possible to have both valves closed and the piston NOT be at the top...this is called the OVER LAP....
    Once you verify this and the harmonic balancer is on "o" degrees drop in the distributer with the rotor cap off. make sure the rotor button clip is pointed toward the #1 piston......lock down your cap ...then contiue to roll your harmonic balancer around to what ever degree you want the final timing mark set on ..examle: 36 degrees.


    if your harmonic balancer was installed properly at "TDC"..This process will be dead on target and fire up No problems...


    note: if this is a high performance motor there will be some issues on installing the cam on the marks straight up and down..normal low performance street motors this is a ok method..

    Good luck.

    Brian
    Bjuice..

    "I'M YOUR HUCKLEBERRY ! "

  6. #6
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    i've got the distibutor pointing at #1 when the balancer reads tdc.so if i rotate the balancer to36 degrees and lock down the distributor that should work? i'll give it a try i've worked on quite a few sbc and this is the first time i've run into this sort of problem.
    as for the cam its got a 4 degree advance ground into it and it stated in the instructions to install it straight up.this an 11.1 street motor will this hurt my hp numbers?
    thaks seth

  7. #7
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    Just an FYI I have a " dead stop " I made from using a " non fouler " spark plug adapter and taping it for a 3/8 - 16 thread and then using a corresponding bolt in it

  8. #8
    Senior Member MASTER BUILDER
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    Yes you can actually static time your engine by setting the harmonic to the degree you want to fire, you can confirm this with a VOM thru your pickup.
    we had a similar problem with idle on a ford we were working on, seems the springs on vac advance were a bit loose and when hooked up the timing would jump one cylinder, it seems you have the same problem but in reverse.

  9. #9
    Administrator RACING JUNKIE bjuice's Avatar
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    Quote Originally Posted by chev78
    i've got the distibutor pointing at #1 when the balancer reads tdc.so if i rotate the balancer to36 degrees and lock down the distributor that should work? i'll give it a try i've worked on quite a few sbc and this is the first time i've run into this sort of problem.
    as for the cam its got a 4 degree advance ground into it and it stated in the instructions to install it straight up.this an 11.1 street motor will this hurt my hp numbers?
    thaks seth
    ok just make sure you take off the valve cover and make sure both valves are closed and the piston is at the top....just shine a flashlight in there and you can see yher piston at the top of you can get down there to it..if not a coat hanger or anything like that will do........make sure the distributer is dropped in pointing toward #1...then roll harmonic on around to your desired degree mark.. hit the igintion...you should be able to lock the distributer down right where you dropped it in.....


    by reading your 1st post it sounded to me that you propbaly did aLL THAT I mentioned but you did not roll the balancer on around to the timing desired..WHICH WOULD RESULT IN LOW TIMING...WHICH WILL ACXT JUST LIKE YOU WERE DESCRIBING IT WOULD....
    OR YOU COULD HAVE HAD BOTH VALVES CLOSED BUT THE PISTON BE AT THE BOTTOM OF CYLINDER...( A COMMON MISTAKE)..

    if you do this properly it will work 100% guaranteed...

    if you have any problems setting up the timing..give me a call and i will walk you thru it..864-607-6511.....if i do not answwer leave a message and i will call you back, when i am in the shop my cell phone doesn't pick up incoming calls..

    BRIAN


    let us know how it turned out.


    Brian
    Bjuice..

    "I'M YOUR HUCKLEBERRY ! "

  10. #10
    Administrator RACING JUNKIE bjuice's Avatar
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    Quote Originally Posted by chev78
    i've got the distibutor pointing at #1 when the balancer reads tdc.so if i rotate the balancer to36 degrees and lock down the distributor that should work? i'll give it a try i've worked on quite a few sbc and this is the first time i've run into this sort of problem.
    as for the cam its got a 4 degree advance ground into it and it stated in the instructions to install it straight up.this an 11.1 street motor will this hurt my hp numbers?
    thaks seth

    YOU SHOULD BE OK BEING A STREET MOTOR...
    I DID IT THAT WAY OVER 25 YEARS AGO WHEN I WAS REPLACING HYDRAULIC CAMS IN MY 70 CAMARO I DROVE TO HIGH SCHOOL..


    BRIAN


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