Engine Dyno Questions!

Electrical and Ignition

  1. Pale340

    Pale340 Pale340

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    Hey all,
    My 1973 340 engine is about ready to go to the dyno. The problem is, the guy I am taking it to is local and says he is not sure how to set up the ignition due to there being the ECM and ballast resistor. I want to run it with the distributor that is going in the car. So, how can I do that? Is there a way to set up the ignition on the engine stand to run without the ECM, ballast resistor, etc? Can I not just supply 12 volts to the coil? I am a bit upset that I have to figure this out. I would think a guy that has been doing engine runs for the last few years would know more. However, he states he has not run a Mopar with electronic ignition and wants to make sure it is set up correctly. I will be the first. Any help would be great. Thanks.
     
  2. Plymouth 65

    Plymouth 65 Floorable Deplorable

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    It's actually pretty simple, do you have the 4 or 5 pin ECM? 65'
     
  3. Pale340

    Pale340 Pale340

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    I will have to look. It's a 1973 if that helps.
     
  4. 67Dart273

    67Dart273 FABO Gold Member FABO Gold Member

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    If you do not have a separate ignition harness to fit the box it might be simpler to "not" use the Mopar.

    If you have an aftermarket ignition harness just pull it out and hook it up. You VERY LIKELY DO NOT HAVE a 5 pin box even if wired that way

    Another way around the problem is to go down and buy a GM 4 pin HEI module. Scare up a small piece of aluminum for a heat sink and wire that up

    If you look at the 4 vs 5 pin wiring, ONLY THE SECTION OF THE RESISTOR on the left has been eliminated and is not needed. If it "is there and wired" it will not hurt anything on a 4 pin box. The BOX MUST BE grounded. The "existing wire" labeled at top right is the 12V power.

    Ignition_System_4pin.jpg

    Ignition_System_5pin.jpg

    Or wire up a GM 4 pin HEI module

    The module has a locating "tit" on the mounting surface. You will either have to cut/ file that off, or drill a clearance hole in your mounting plate/ heat sink. The ground connection is one of the mounting holes. NOTE the diagram of the distributor hookup. They must not be reversed

    4pin-jpg-jpg.jpg
     
    Last edited: Sep 10, 2021
  5. Plymouth 65

    Plymouth 65 Floorable Deplorable

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    Here's both diagrams 2 (1).gif 1.gif
     
  6. Pale340

    Pale340 Pale340

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    I have the stock 1973 set up. The ECM is new, the ballast resistor is new, the distributor has been rebuilt and restored to the engine specs. I do have the original engine harness if I need the hook up to the ECM and ballast resistor.
     
  7. pishta

    pishta I know I'm right....

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    should just be 2 wires to hook up to his equipment off your ignition, start and run.
     
  8. Pale340

    Pale340 Pale340

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    Do I have to use the ECM and ballast resistor to use the original distributor?
     
  9. Scody21

    Scody21 Just send it

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    That’s what I was thinking. I have the stock distributor pickup wires hooked to an Mopar 6al box in the Ratty 73 swinger, so I can run it before fixing the wiring in the engine bay..
     
  10. 67Dart273

    67Dart273 FABO Gold Member FABO Gold Member

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    Maybe "I assumed" Is this out of the car or in the car for the dyno?

    You need SOMETHING for electronics which is why I posted the GM HEI as an alternative. If you or the dyno shop has an MSD you could us that as well What does HE have for electronics
     
  11. Mattax

    Mattax Just the facts, ma'am FABO Gold Member

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    * To use the original distributor, it can be connected with the correct polarity to any ECM that works with magnetic pickups.

    * To use the original coil, it must be used with a device that regulates the current to the coil. A resistor is one method that for years was the most common. HEI units electronically controlled the current. CD units supply an electric pulse so no other regulation is used. For a standard ignition, if you are running the engine off of battery (12 Volts more less) you can probably get away with running a few pulls at full voltage with no current regulation. If you are running the engine off of an alternator (14.5 Volts more or less) its more likely to overheat and damage the coil.
     
    Last edited: Sep 10, 2021
  12. Mattax

    Mattax Just the facts, ma'am FABO Gold Member

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    When you go on the dyno, my suggestions are:
    1. Know what the advance curve in your distributor looks like. Ask your distributor rebuilder for exactly what the advance specs it has.
    A factory distributor of that era had a lot of advance early. You'll want to set timing for a dyno pull by measuring the timing on the engine at mid and high rpm. At minimum check timing at 2800 rpm and 4000 rpm. Plug the vacuum ports on the carb and/or intake. Dont use the vacuum advance for dyno as it plays no role at WOT.

    2. From the dyno run, make sure you get power, AFR and or fuel consumption for the entire range of the pulls. Find out what rate the dyno will be run (600 rpm/sec is common but not universal). If possible get MAP.

    Here's some threads about dyno pulls. They will give you an idea of the different things people look to learn or accomplish in a dyno session.
    383 rebuild - kinda whimpy on the dyno?

    How to prepare for engine dyno?

    340 on dyno video, whats your opinion

    Don't want to spend the effort and money and then be wondering about what was done or measured.
    Need Opinions. Have nothing to compare to.
     
    Last edited: Sep 10, 2021
  13. Pale340

    Pale340 Pale340

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    The engine is out of the car. No alternator, thermostat, fan, etc. It has the fan and crank pulley only. Fuel pump block off plate installed. Will be running with stock exhaust manifolds, restored original thermoquad carb that was tuned for my engine specs. Stock distributor restored and tuned to my engine specs. Stock reproduction coil.
     
  14. Scody21

    Scody21 Just send it

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    I assume the motor is fresh? You have the inner valve springs pulled for brake-in if non-roller cam? And then put back in before any power pulls are made...
     
  15. AAndrews

    AAndrews MOPAR .. Move Over, Plymouth Approaching Rapidly!

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    I agree with you!

    Anyone doing this type of work should know the basics of all ignition systems including Mopar. If I was in this type of business, I would figure it out on my own and get the appropriate equipment needed to do the job. After all , you are paying for his expertise. Personally, I'd walk from this guy!
     
  16. Bewy

    Bewy Well-Known Member

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    if it has a new flat tappet cam, it is imperative that the engine start quickly & without excessive cranking. That means:
    - carb filled with fuel
    - dist installed correctly & timed for 10-20* BTDC for cam break in
    - ign wired correctly for spark
     
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