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TBI swap timing

Discussion in 'The Injection Section' started by CB77GMC, Sep 7, 2006.

  1. CB77GMC

    CB77GMC 1/2 ton status GMOTM Winner

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    Stock 77 350 w/headers just did a TBI swap from a 87 350 used adapter plate for TBI on stock Q-junk intake. Truck runs great good power at 6* btdc and at 0* TDC runs fine but no power. Disconnected hei when I set timing. Any ideas :confused:
     
  2. bigblock72

    bigblock72 1/2 ton status Premium Member GMOTM Winner

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    Sounds about right, if it runs good with no detonation then run it. On my own truck I set the timing at 8* and that's with 5-6 pounds of boost. If it really bothers you you can have a new chip burned with more agressive timing maps.
     
  3. 1979jimmy350

    1979jimmy350 1/2 ton status

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    did you use the distributor that came with the TBI or the stock one? If you have the stock one thats your problem, if you have the TBI style you need to disable the advance when you time it
     
  4. btolenti

    btolenti 1/2 ton status

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    I had the same issue on my TBI swap on my 86. It ran, but had no power, at 0 degrees (with the timing wire disconnected). I went ahead and ran it a 4 degrees and it was much better. Just make sure you listen carefully for any pinging. As long as there is none, don't worry about it.
     
  5. CB77GMC

    CB77GMC 1/2 ton status GMOTM Winner

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    All of the 87 TBI stuff was used tank w/pump, fuel lines, sensors, distrubutor, ecm, and wiring. Distributor wire was disconnected each time timing was set and reconnected when testing.
     
  6. sweetk30

    sweetk30 professional hooker Premium Member

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    cam might have been swaped or timing chain in the past. and someone set it from dead zero to get more power. this might just be a possibility.
     
  7. CB77GMC

    CB77GMC 1/2 ton status GMOTM Winner

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    I've been thinking about that or chain may have jumped tooth. RV/Towing cam is on my todo list so I will find out then if chain is off.
     
  8. southernspeed

    southernspeed 1/2 ton status GMOTM Winner

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    Chains don't jump teeth but it could just be that the TBI ecu doesn't like the cam you have. There are specific cams for TBI motors which are actually quite mild. You can run lumpier cams but you'll have to enter the dark and mysterious world of chip burning, or emulating as it seems most people do these days(me included).
     
  9. 94yukon

    94yukon 1/2 ton status

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    Do you have a scan tool with data stream ability ? if you do see what the trouble codes are if you swapped the TBI system in. I dont think your check engine light is hooked up ? take your tool set it up watch the timming as you drive down the road make sure you are get up to 32-34 deg. the stock distrub. timming is 0 deg. for most stock TBI's. I had knock sensor codes the sensor was bad and on the one wire knock sensors dont use pipe tape on them. They need a good ground. I went to NAPA and ohm out 4 sensor to find the right one . runs good now good luck!!
     
  10. CB77GMC

    CB77GMC 1/2 ton status GMOTM Winner

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    Check engine light is hooked up and works no codes. I should have ALDL cable made soon so I can check data.
     
  11. dyeager535

    dyeager535 1 ton status Premium Member

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    My MAF TPI system is the same way. Huge difference +/- 2* of what it likes. (Believe I ended up at 4*, temp until I actually start modifying the prom) Stock, base timing idles fine but obvious loss of power.

    Changing the engine/components without modifying the chip will do that to you. :)
     

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