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Old 06-30-2006, 08:05 AM
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Correct schematic for engine test stand?

I'm getting set up for running my hemi on a test stand, and need some input on my electrical needs.
I've read through almost every thread on this forum, and I think I have it down pretty good, but I just want to run it by everyone to see if I'm on the right track.
First, I'll list the hardware, so you know the setup:
Engine is 392 hemi, carbureted.

Distributor is Vertex "Mag style" electronic P/N 541804. It has its own integral coil. Three wires, one is +12v(black) to trigger assembly. One is +12v(red) that is run through ballast resistor to coil. Vertex says that this resistor must be used.

Starter is Mopar lightweight starter P/N 5249644. Two terminals, one large lug for battery, and one small terminal which I assume to be the "S" terminal.

Alternator is Powermaster P/N 67293 140 amp 1 or 3 wire operation. I will probably run it one wire for now, even though I don't need to have it hooked up for running on the stand. When I put it in the car, I'll do a 3-wire setup.

Fuel pump is electric Carter P4070. Fan is electric that I had on hand, will fit on the radiator nicely.

Ignition switch is Painless wiring universal switch.

I'll be using mechanical oil press. and water temp. gauges, so there will be no electrical hookup.

Attached is the schematic that I did, so let me know if I got it right.....

Only a couple areas of concern: I've read a lot about a "secondary ignition" from starter to coil side of resistor (or distributor). Vertex says that I may need it, but I think that is based on if I am using a factory harness and switch. The ignition switch is energized this way: ST terminal energized in "start" only, IGN terminal energized in "run and "start" only, and ACC terminal energized in "acc" and "run" only.
The other thing is if I do need a secondary ignition, will I also need a starter relay to accomplish this? The starter doesn't have the correct connections for this, I don't think.
Since this is only a run-in, will relays be necessary on the fan or fuel pump circuit?
Do I have a chance of run-on after switch is turned off?

I have not wired this up yet, I wanted to get the correct wiring figured out before I start.
I hope I included all info, please let me know if I'm good to go.
I'll include both a .jpg and .pdf version, hope it works!


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Last edited by steve392; 06-30-2006 at 08:23 AM.
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Old 06-30-2006, 03:54 PM
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Doc here,

First off, that is a very good drawing, did you make it? and If So what software are you running, I'd like to find something like that..

Next, the only changes I could add to make that better..would be on the FAN circuit, I would run a 30 AMP maxi fuse and a relay, AND upgrade the wire to 10 gauge..for two reasons..

One, the Fan may spike higher than 20 amp on startup and under other conditions opening that fuse..Startup current can be very high compared to "Run" current.

Two, Wired direct to the Ignition side of the switch, It can rob power from the Ignition module..causing poor performance ...AND when you shut it down, the collapsing fields can hold the ignition high..and run~on Can occur..

By installing a relay, you bypass all those possibilities..just hook the Normally Open Contact to a 10 Gauge wire, Via 30 Amp Maxi fuse, to the battery, The Center wiper to the Fan Via 10 gauge wire..Then hard ground the coil, and run power to the "I" side of the ignition switch..This will isolate the fan motor from the ignition circuit..and carry more power to the motor. At the VERY least I'd install an isolation diode ...

If you need a Secondary Ignition, you Can install a relay from the "S" side of the switch or solenoid and hard ground the other side of the coil..Run a 10 gauge wire from the battery to the normally open contact, then the center wiper to the ballast resistor..This way the contact will close and support power to the ignition anytime the start function is in use..

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Old 07-01-2006, 07:16 AM
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just passin' thru
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Thanks for the reply, Doc. I'll go with the relay on the fan circuit. I can't wait to get this motor up and running...

The drawing was done by me using AutoCad, which I use at work. I exported the drawing and converted it to a .jpg format. Aside from the black background, it came out well.

Thanks again for your help,

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