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MSD wiring for 77 Hornet AMX |
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Extract2th 
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Joined: Jul/17/2009 Location: Genesee, PA Status: Offline Points: 416 |
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 Topic: MSD wiring for 77 Hornet AMXPosted: Jul/15/2012 at 11:01am |
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I am cutting this from my project thread to see if I can get some input here:
The 360 I picked up has the MSD cap a dapt on a motorcraft distributor. I have seen a couple posts in the past regarding the MSD requiring the full 12 volts and to bypass the resistance wire. I intend to replace the stock breakerless ignition unit (believe it to be the ford Duraspark ignition, correct me if I am wrong for the 77 Hornet) with the MSD 6AL. Some individuals have mentioned using a relay to seperate the MSD wiring from the stock harness to achieve the full 12 volts. So here is the wiring diagram for the 77 hornet and gremlin.  And a close up of the ignition wiring:  And now the MSD wiring for the Ford Duraspark ignition:  Am I correct in the assumption that the wire I will want to connect the MSD red (non battery wire) to is the stock yellow that runs to the coil + that I have the black circle around in the close up pic that runs from the ignition switch? Can this be done without using a relay since the MSD unit is getting its power from the Battery itself (thus bypassing the resistance wire). Or should the yellow wire be used to trip a relay that then provides a full 12 volts into the red (non battery wire). I am hoping to be able to reconnect my factory tach to this after and am aware that I may need the tach adapter. I would rather ask, as I am sure others here have done this, before I cut into anything rather than fix it later after I screwed it up. |
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Shane Blake
Current Cars & Projects: 1968 AMX 1970 Gremlin 1970 Javelin SST 1973 Javelin 1977 Hornet AMX 1979 Spirit AMX 1988 Eagle wagon Parts Cars/Future Projects: 1970 Javelin SST, 1972 Gremlin |
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gwryder
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Joined: Jun/30/2009 Location: Michigan Status: Offline Points: 710 |
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Posted: Jul/15/2012 at 11:11am |
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This is a totally ignorant guess, because I'm not familiar with 77 Hornet electrical. Since 1975 most vehicles came stock with electronic ignitions, so there should be no resistance wire to the coil. The only reason for the resistance wire or ballast is to protect the points from burning up. With transistorized ignition, the output transistor can handle the full 12 volts dropped across the coil. No points, so no resistance wire.
John
Incase I'm wrong, follow the link to a good relay for your setup.
Edited by gwryder - Jul/15/2012 at 11:16am |
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John
70 AMX |
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FuzzFace2
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Joined: Jul/05/2007 Location: Angier, N.C. Status: Offline Points: 10356 |
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Posted: Jul/15/2012 at 12:22pm |
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From what MSD has & the AMC print I would say that is what has to happen to get it to work.
Now the $84 question, is that yellow wire a resister wire or not? I cant see what it says under the dot/arrow if it says a resister wire or not? Could test it to see what the voltage is when first turned on and what it is after a few min.
Another way I "think" is on the older cars that use a resister wire the wire runs from the IGN. Sw. to the starter SOL. "I" lug and from there to the coil + side. It is done so the IGN system gets full 12 volts when the motor cranks to give it a hotter spark for starting.
I run the MSD6L on my drag car but I dont use any of the stock wiring or gauges.
Dave ----
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TSM = Technical Service Manual
75 Gremlin X v8 for sale 70 Javelin 360/auto drag car 70 Javelin 360/T5 Street car |
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Extract2th
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Joined: Jul/17/2009 Location: Genesee, PA Status: Offline Points: 416 |
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Posted: Jul/15/2012 at 9:41pm |
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[QUOTE=FuzzFace2]From what MSD has & the AMC print I would say that is what has to happen to get it to work.
Now the $84 question, is that yellow wire a resister wire or not? I cant see what it says under the dot/arrow if it says a resister wire or not? Could test it to see what the voltage is when first turned on and what it is after a few min.
Another way I "think" is on the older cars that use a resister wire the wire runs from the IGN. Sw. to the starter SOL. "I" lug and from there to the coil + side. It is done so the IGN system gets full 12 volts when the motor cranks to give it a hotter spark for starting.
I run the MSD6L on my drag car but I dont use any of the stock wiring or gauges.
Dave ---- [/QUOTEThanks for the input. Under the dot/arrow it states throttle solenoid. After mulling this over for a bit, I recalled that the TSM for 77 had 3 supplements to it, so luckily I dug them up and one is specific to the Hornet AMX. Lo and behold there is a wiring diagram in the back. I will post a pick of this as I am sure it might be helpful to someone else in the future:  So it appears that the Hornet AMX tach is wired in series much like my 70 Javelin was. So the tach must be current sensing rather than voltage sensing. The tan wire connected to the original coil + connector bypassed the Coil + to go to the tach +. The black w/tracer returned from the tach negative to the coil positive. So my thoughts now are to go off the yellow that the tan splices off of to connect to the red (non battery) for the MSD 6AL. The unit has a tach wire available, but I will probably need to use their tach adapter (MSD8920) to add the tach support with magnetic pickup. Or would it be possible to connect the MSD red wire to tach negative? Since the control would be through the MSD unit itself rather than retaining any stock control, I tend to think not. Anyone familiar with the radio suppression capacitor connector. Will I need to retain this? |
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Shane Blake
Current Cars & Projects: 1968 AMX 1970 Gremlin 1970 Javelin SST 1973 Javelin 1977 Hornet AMX 1979 Spirit AMX 1988 Eagle wagon Parts Cars/Future Projects: 1970 Javelin SST, 1972 Gremlin |
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PHAT69AMX
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Joined: Jul/07/2007 Location: West Virginia Status: Offline Points: 5926 |
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Posted: Jul/15/2012 at 11:20pm |
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Unfamiliar with the latter model AMC wiring.
A good "clean" full 12 volts to the large MSD Red Power wire, yes.
But understanding is when using an MSD Box
the voltage on the stock Coil wire doesn't really matter
because the MSD box is just seeing it as a "switching signal"
and the MSD box and it's own two wires to the coil are now "feeding" the coil
and have "taken over" those duties from the stock coil wire(s).
Getting the stock Tach to work is a seperate issue.
Been a long time, but got my stock '69 Tach to work without a "Tach Adapter".
How to do it as you've mentioned depends on what type of Tach, Volt or Amp triggered.
Appears yours is the same as a '69 since it has only (2) wire posts other than the illumination.
To get mine to work it requires the use of a single Ballast Resistor.
NOT to effect the coil feed volatge, but rather used in a different way.
Here's a diagram I made and had already uploaded here for use before.
If the MSD Box is "white wire" triggered or not may make a difference
if this diagram applies or not, "white wire" triggered is used only if
the distributor is NOT a magnetic pickup iirc.
Mine is "white wire" triggered since I'm using a UniLite conversion in stock Delco dizzy.
Writing this I'm unsure what dizzy you're using, iirc it was a HAL effect Motorcraft dizzy
and that may make this diagram invalid as to how to make the stock tach work sans adapter.
 Edited by PHAT69AMX - Jul/15/2012 at 11:24pm |
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