Engine Test Stand - how to wire

Discussion in 'Troubleshooting & Diagnosis' started by steve78LT, Sep 24, 2017.

  1. steve78LT

    steve78LT Veteran Member

    244
    1
    Nov 30, 2003
    Barre, MA, USA
    Not sure which forum this one belongs in...

    I'm using a basic engine cradle as a quick test stand to make sure things run and don't leak before dropping the motor in. Not looking to build a full-blown stand for tuning or cam break-in. This was a running motor that I just cleaned and painted and re-gasketed. I just want to run it for a minute or two, to see that it runs.

    For this test, I don't have the front accessories on. No water pump (won't be run long enough to worry) and no alternator (want to just run it off the battery).

    I'm looking for some help on the wiring.

    I have a battery with a set of jumper cables connected as follows: battery negative to block and battery positive to the big post on the starter. Then I have a bump switch clipped to the s-terminal on the starter and positive cable on the big post. That works fine - press the bump switch button and the starter spins the motor.

    What do I wire to get power to the distributor ('78, HEI) so the motor has spark? I ran a wire from the positive post on the battery to the BATT terminal on the distributor, but the coil got really hot, so I'm not sure that's right. Before I wreck something, can anyone tell me the right way to wire it?
     
  2. l16pilot

    l16pilot Veteran Member Lifetime Gold Member

    1,475
    53
    Dec 13, 2004
    Hurlock, MD, USA
    What do I wire to get power to the distributor ('78, HEI) so the motor has spark? I ran a wire from the positive post on the battery to the BATT terminal on the distributor, but the coil got really hot, so I'm not sure that's right. Before I wreck something, can anyone tell me the right way to wire it?

    The beauty of HEIs is that is requires just the one +12V connection...simplicity. However, it should be a switched 12v. How long was the 12v connected before the coil became noticeably hot?

    IMO, I would not start a gasoline engine without circulating coolant. Combustion chamber temps can spike really quick and do damage you may not readily see. Besides, to really check for leaks and issues, the engine needs to be brought up to temp and stabilized. Again, just my opinion, but it would be a shame to o harm to the engine if it can be avoided.
     
  3. mrdragster1970

    mrdragster1970 Veteran Member Lifetime Gold Member

    .


    Use a high amp toggle switch, not a direct line to HEI, or get an actual ignition switch and use ford noid.


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  4. budro6968

    budro6968 Veteran Member

    1,196
    123
    Apr 2, 2016
    Jax Florida
    If you have the engine hoist use that to steady the engine and put blocks at the M/M's put on the water pump with the accessories needed to run the pump leave the fan off and hook up the hoses to the rad. They should hold the rad in place just to run for a few mins. Use a box fan to cool the rad. I just run a hot wire to the Bat and the Batt terminal on Dist. with alligator clips. The rest sounds like you got figured out. Maybe put some padding under the rad so it doesn't vibrate on the deck.
     
  5. steve78LT

    steve78LT Veteran Member

    244
    1
    Nov 30, 2003
    Barre, MA, USA
    Thanks guys.

    I figure I had a wire from the battery to the batt terminal on the distributor for maybe 10 minutes while I fiddled with things, before I felt the cap getting hot. Think that smoked the coil? I'll look around for a toggle switch.

    Good point about the water though. I will through the water pump on and fill the block too. Instead of a radiator I may just run hoses to a 5 gallon bucket and take the thermostat out. Shouldn't heat the water if it only runs a couple of minutes.
     
  6. Rdobbs1977

    Rdobbs1977 Veteran Member

    261
    8
    Dec 1, 2014
    TN
    i think pilot got ya covered. Would not hurt to at least run an oil pressure gauge while you're at it, at the very least
     
    l16pilot likes this.
  7. mrdragster1970

    mrdragster1970 Veteran Member Lifetime Gold Member

    .


    Great tip, oil gauge might just save your ass, and even a cheap mechanical model will be good enough for 60 seconds.


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  8. steve78LT

    steve78LT Veteran Member

    244
    1
    Nov 30, 2003
    Barre, MA, USA
    Thanks for the help guys. Picked up a heavy duty toggle switch at the hardware store. Plumbed an oil pressure gage and spun the motor up to see pressure first. Did fill the block with water to get something in there. Had no spark - charged the batter overnight (saw about 13.5V) and swappped the coil out - fired on the 4th crank.

    So to summarize and hopefully help the next guy out:

    - jumper cable from negative post to anywhere on the block.
    - other jumper cable from positive post to the fat post on the starter.
    - decent gage wire from the battery positive post, through a toggle switch, to the batt+ terminal under the distributor cap.
    - if you use a starter bump switch, clip one side to the fat starter post and the other to the small starter post.
     
    HawkX66 likes this.

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