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350 Conversion - Electrical or Fuel?

Discussion in '40- & 55-Series Tech' started by DJSH, Mar 16, 2004.

  1. DJSH

    DJSH

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    '87 FJ60 w/ Chevy 350. I have an HEI distributor set-up and am having difficulty with hesitation and notice it is consistent with the stock RPM Tach needle jumping around. I checked the cap and coil for arching and did not see anything. The rotor has some "charcoal" dust on it, but no obvious arching there either. So, I am thinking it is probably a combination of electrical and fuel, but before I replace/rebuild the carb, I want to trouble shoot the electrical. Does anyone have a similar experience or ideas they might be able to share? I use the power from the LC coil green connection, could this be the problem-do I need to route power from the battery?

    Thanks for any help,

    Dave.

    '87 FJ60 147K Chevy 350
    '97 FZJ80 70K
     
  2. Cruisergreg

    Cruisergreg

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    With the tach dancing I'd suspect the ignition module is flaky. Also, IIRCC, the ignition power source should be the large white and black wire coming from the ignition switch; if you route power directly from the battery you'll never be able to turn the ingnition off. The green wire is the tach signal I think, although it's been a few months since I did my wiring.
     
  3. theo

    theo

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    HEI needs full voltage at higher amperage than standard ignitions. Many folks do this by running battery voltage through a relay with 10ga wire. You can use your existing switched wire to control the relay. I would try that first. :)
     
  4. Yoda

    Yoda

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    Rplace the rotor. I have seen many that fire through the rotor.
    Check the wires that are inside the dist. Small wires run from the pickup coil to the ign module. They can fatigue (pull very gently on them...if they move or stretch, replace the pickup coil) Reason is,they flex every time the vac advance moves. Step on gas, advance moves, wires flex, open circuit= no spark.
    Check under the coil to make sure the sheet metal ground strap is there
     
  5. DJSH

    DJSH

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    Thanks for all the feedback. I am in the process of wiring power through a relay to the HEI to see if that helps. Do people put fuses in line from the battery to the relay and relay to the HEI, or, is there no need for a fuse / circuit breaker?

    Honestly, I am confused as to why the tach dances consistent with the engine running poorly on acceleration. Sure hope this works.

    Thanks,
    Dave.
     
  6. theo

    theo

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    Good idea to fuse any new circuit. Only 1 needed between the battery and the relay. The switched wire you choose should already be protected if it's part of the original wiring.

    Honestly, I don't know if this will solve your problem, but I'll bet you'd eventually have trouble if you didn't upgrade the wiring. :)
     
  7. Rice

    Rice SILVER Star

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    Before performing the rewire you may wish to "hotwire" the ignition from the battery for a test run and see if it corrects the problem. If you do end up running new wire and a relay I suggest using a fuse on BOTH parts of the relay circuit.
     
  8. DJSH

    DJSH

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    Thanks for the advice. I thought about the "hotwire" but realized I would have to switch it to turn off the motor...then again, I guess I could use a quick disconnect from the battery and disconnet to shut off the motor. As for the relay, I have a circuit breaker that auto resets itself when shut-off by the ignition, I will put that between the relay and HEI probably.
     
  9. DJSH

    DJSH

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    here is a picture of the conversion
     
  10. DJSH

    DJSH

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    Just completed a test drive after wiring direct from the battery to the HEI...no hesitation :beer: ran like a champ throughout the powerband

    Thanks for all the advice.

    :cheers:
    Dave.
     
  11. DJSH

    DJSH

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    Update

    I finally upgraded the carb to a new Thuder Series Off Road from Edelbrock - http://www.carbs.net/edlthunder.asp

    100% improvement in driveablility. HOWEVER, the tach is dancing again. This time at idle and under load. Sitting at idle the tach will dance consistent with the engine running rough. Any ideas, could it be the ignition module or pick up coil or??

    Thanks for all the help. Soon to come BDS lift and 33's.

    Dave.
    '87 FJ60 150K Chevy 350
    '97 FZJ80 75K
     
  12. DJSH

    DJSH

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    anyone experience similar symptoms?