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MSD 8523 Dist with Factory Tach

Printed From: TheAMCForum.com
Category: The Garage
Forum Name: AMC V8 Engine Repair and Modifications
Forum Description: AMC-made V8 engine mechanical, ignition and fuel from basic repair to high-perf modifications
URL: http://theamcforum.com/forum/forum_posts.asp?TID=96669
Printed Date: Jun/25/2019 at 5:02pm


Topic: MSD 8523 Dist with Factory Tach
Posted By: Someassemblyrqd
Subject: MSD 8523 Dist with Factory Tach
Date Posted: Oct/04/2018 at 6:02pm
White70, Rodhhrod, WesternRed, and others, I've talked to each of you on this subject, so if you have more to add, I'd appreciate your comments.

I've been studying the TSM Tach schematics in order to integrate my MSD 8523 Ready-to-Run Dist. and Blaster II with my factory 8K tach.   I believe I have to solution, but would like input.

The MSD installation manual says to connect the dist. orange and red wires to the coil and have 12v feeding the coil for power. I don't believe the factory 8K tach will handle a full 12v as the TSM schematics indicates a lower voltage with the use of the double yellow wire connection at the I terminal of the solenoid.

It's the MSD dist that requires 12v to operate correctly. I BELIEVE the coil works at its best at 12v, however, if the Blaster II is used with a points dist., a ballast resistor is required thus running at a lower voltage.

So, the drawing below shows my wiring of the MSD dist as well as the TSM tach wiring from the I terminal to the tach, then to the coil. I removed the MSD recommended RED wire from the + side of the coil and connected to the ignition 'run' wire to meet the 12v requirement of the dist.   The tach worked flawlessly.

So, my question is: if a points dist. requires the Blaster II to incorporate a ballast resistor, therefore, running a lower voltage so as not to burn up the points, why can't I run the same lower voltage (power feed from the double yellow wires through the blue tach wire)to feed the coil AS LONG AS I have a full 12v requirement feeding the MSD dist.?

What are your thoughts?



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Greg E.



Replies:
Posted By: rodhhrod
Date Posted: Oct/07/2018 at 12:16pm
Very nice work on this, this has been an issue for a very long time. If this works, it will save folks a lot of money on tach conversion. I hope folks who try this will post results. I have already done the tach conversion years ago.
Congrats    ClapClap


Posted By: rodhhrod
Date Posted: Oct/09/2018 at 9:58pm
I am really surprised that no one has posted a comment on this.


Posted By: White70JavelinSST
Date Posted: Jan/11/2019 at 4:54pm
I don't know how I missed this thread.

I don't recall using any thing other than the Billet ready to run MSD distributor and wiring it into the ignition circuit and AMC factory in dash 8K tachometer circuit somehow.  I wish I could remember. I will have to take a look at it to refresh my memory, I did this conversion at least 10 or 12 years ago and have been putting 1500 to 2000 miles on the car each year after, no troubles with tachometer or distributor.


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70 Javelin SST, second owner, purchased 1972


Posted By: 092171michael
Date Posted: Jan/24/2019 at 8:41pm
Ok, AMC forum people, I'm your newest member and I'm having some serious electrical issues. I put the RTR msd distributor in my car (1970 javelin) with the blaster coil. I used the old wires that went to the coil on the new coil. Car wouldn't run. Until I put the battery charger on because the battery started to die. Then I figured out, I  wasn't getting 12 volts to the coil (then distributor ) to run. MSD told me to run a jumper right off the battery to the coil to make sure not an engine problem.  With jumper wire, car ran great.  So, now I'm trying to figure out how to wire it correctly with 12 volts, without cooking something else. Looking at the diagram in this thread, please explain what a "9 volt resistance wire" is. My car has the factory tach. Does that mean using the regular yellow tach wire? Or installing something else? One more thing. What is the "double yellow" wire on the solenoid? My car has the pink/yellow wire at the solenoid, which it says to leave unattatched, but I  have no double yellow wire?! I  have green wire at the solenoid for neutral safety switch. And blue tach wire. No other wires at solenoid. The 3 yellow wires that went to the original coil- 1 from the tach, 1 from voltage regulator,  and one from the solenoid  (attatched to the same plug as the pink wire) Please help. Once this problem is figured out, I  have 2 more I need help with. 


Posted By: Trader
Date Posted: Jan/24/2019 at 9:43pm
The original point ignition system used a resistor between the ignition and the coil to reduce amperage so points would not burn.
Everything in the ignition system, including the tachometer were built around this.
Now an MSD distributor needs full system voltage - typically 14.2, no resistor.
The MSD distributor puts out multiple spark firings per cycle - not one like the points. The old tachometer cannot read this.
MSD sells a box for old tachometers to make a single pulse.
This voltage reduction resistor can be doing the same thing by reducing signal so only one pulse is seen by the tachometer.
A capacitor with the resistor to filter the pulses should work better, I believe this is what the expensive MSD box basically is.


Posted By: 092171michael
Date Posted: Jan/25/2019 at 12:43pm
Wow, there were a lot of complicated words in your response. (I'm not mechanically inclined) Here's what I know. Putting the battery charger on high, hooked up to the battery, with original 3 wires going to the coil. Motor runs great, and tach works. Unhooking 3  wires going to coil and running jumper wire from battery to coil without charger on, car runs great, but no tach. (Because tach wire isn't hooked up)  But can't shut the car off. So, if I run red power wire to column "run" wire for 12 volts, can I  rehook up the tach wire directly to the coil and be ok. Or will to much juice somehow get to the tach and hurt it. Also what about the other 2 yellow wires? I  understand I can probably leave the one going to the voltage regulator unhooked,but the other one? And they're hooked together at the coil. Also, witch wire actually starts the car?


Posted By: Trader
Date Posted: Jan/25/2019 at 1:35pm
The diagram above works but disconnect the yellow wire to the tachometer completely.
Ensure the wire 12 VDC from the ignition switch does not have a resistor in it. Full system voltage to the distributor.
The MSD 8523 should have a grey wire off the distributor terminal. It may or may not operate your tachometer. If it does not then buy the MSD box for the tachometer or you can try some other "filter". But be warned that tachometers are voltage sensitive and can be "fried" easily.


Posted By: Someassemblyrqd
Date Posted: Jan/25/2019 at 3:37pm
Let me see if I can provide some clarity:

MSD says to run 12v to the coil.  From the coil, you’re to run 12v to the rtr dist.   This because the DISTRIBUTOR needs 12v to operate properly.  The blaster II coil will handle 12v optimally but with the AMC tach in-line/in series with this new electronic ignition, it (tach) won’t function properly and will ultimately burn up.
        > The issue with our AMCs is that the existing wiring harness to the disturbutor took voltage from 12v to ~9.6v with the use of a resistance wire (this is the pink wire).  Other manufacturers used an in-line ballast resistor.  Whether it’s a pink wire or ballast resistor, they are doing the same function - cutting voltage to the points they the coil to keep them from burning up.
        >  AMC used the same 9.6v to operate the tach in-line from the power source (blue wire solenoid I terminal) to the coil (+ side) which is a single yellow wire. This is what the schematic above displays
        > Don’t use the rtr grey wire. The wave electrical signal is not compatible with the AMC tach.
        > There is no MSD adapter to interface between the rtr distr and the AMC tach.

So, the distributor needs 12v and you want to have your Javelin to start and turn off with the key 👍.  You need to run a wire directly to the distributor from a 12v source that is powered when the key is moved to the “on” position.   Get yourself a wiring diagram to locate the correct wire at the fuse panel and tap into it.
        >  You’re not going to find this “on” power source in the engine compartment like you have done by directly wiring from the battery.

Now, back to the pink wire.  It is directly connected to a yellow wire.  This yellow wire takes the 9.6v from the pink wire to ‘excite’ the charging system at startup.   AND, the yellow wire also splits off to connects to the double yellow spade connector.  This spade connector is the power source to the coil which fed from the “I” terminal on the solenoid thru the blue wire, to the tach and then to the coil (yellow wire).
        > I believe you have the double yellow spade connector directly attached to the coil.  If so, remove and connect to the solenoid This  is what the schematic above displays

Follow the above, I believe you will have success.


-------------
Greg E.


Posted By: Someassemblyrqd
Date Posted: Jan/25/2019 at 3:39pm
Let me see if I can provide some clarity:

MSD says to run 12v to the coil.  From the coil, you’re to run 12v to the rtr dist.   This because the DISTRIBUTOR needs 12v to operate properly.  The blaster II coil will handle 12v optimally but with the AMC tach in-line/in series with this new electronic ignition, it (tach) won’t function properly and will ultimately burn up.
        > The issue with our AMCs is that the existing wiring harness to the disturbutor took voltage from 12v to ~9.6v with the use of a resistance wire (this is the pink wire).  Other manufacturers used an in-line ballast resistor.  Whether it’s a pink wire or ballast resistor, they are doing the same function - cutting voltage to the points they the coil to keep them from burning up.
        >  AMC used the same 9.6v to operate the tach in-line from the power source (blue wire solenoid I terminal) to the coil (+ side) which is a single yellow wire. This is what the schematic above displays
        > Don’t use the rtr grey wire. The wave electrical signal is not compatible with the AMC tach.
        > There is no MSD adapter to interface between the rtr distr and the AMC tach.

So, the distributor needs 12v and you want to have your Javelin to start and turn off with the key 👍.  You need to run a wire directly to the distributor from a 12v source that is powered when the key is moved to the “on” position.   Get yourself a wiring diagram to locate the correct wire at the fuse panel and tap into it.
        >  You’re not going to find this “on” power source in the engine compartment like you have done by directly wiring from the battery.

Now, back to the pink wire.  It is directly connected to a yellow wire.  This yellow wire takes the 9.6v from the pink wire to ‘excite’ the charging system at startup.   AND, the yellow wire also splits off to connects to the double yellow spade connector.  This spade connector is the power source to the coil which fed from the “I” terminal on the solenoid thru the blue wire, to the tach and then to the coil (yellow wire).
        > I believe you have the double yellow spade connector directly attached to the coil.  If so, remove and connect to the solenoid This  is what the schematic above displays

Follow the above, I believe you will have success.




-------------
Greg E.


Posted By: 6PakBee
Date Posted: Jan/25/2019 at 4:16pm
I'm a bit confused.  If the MSD box is NOT being used, why can't you simply hook it up like this and be done with it?  What am I missing?






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Roger Gazur
1969 'B' Scheme SC/Rambler
1970 RWB 4-spd Machine
1970 Sonic Silver auto AMX

All project cars.



Posted By: White70JavelinSST
Date Posted: Jan/25/2019 at 4:19pm


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70 Javelin SST, second owner, purchased 1972


Posted By: Someassemblyrqd
Date Posted: Jan/25/2019 at 8:24pm
Roger - In your top drawing from MSD, the assumption is a full 12 volts.  But the tach can’t handle the full 12v, or if you assume in the same drawing the voltage is 9.6v from the key to the tach to the coil, the power feed from the coil to the dist is insufficient for it to operate nominally.  The dist needs a full 12v. The tach needs 9.6v as does the charging system to operate properly.  




 


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Greg E.


Posted By: 6PakBee
Date Posted: Jan/25/2019 at 8:49pm
Originally posted by Someassemblyrqd Someassemblyrqd wrote:

Roger - In your top drawing from MSD, the assumption is a full 12 volts.  But the tach can’t handle the full 12v, or if you assume in the same drawing the voltage is 9.6v from the key to the tach to the coil, the power feed from the coil to the dist is insufficient for it to operate nominally.  The dist needs a full 12v. The tach needs 9.6v as does the charging system to operate properly.

 


Are you sure that the tach won't withstand 12 VDC to ground?  Think about this for a second.  What do you think the voltage is at the coil + terminal with the key on, the points open, and the engine not running?  I would bet that it is at full battery voltage.  So what is the voltage at the tach to ground?  Full battery voltage.  As the AMC tach that is being discussed is a series tach that operates from current pulses, not voltage, I am struggling with the concept that it couldn't be wired as I've shown and work.  I would also comment that the charging system (assuming this is a '69/'70 vehicle) does NOT need the 9.6 volts for proper operation as the regulator voltage sensing terminal is between the alternator output and the isolation diode(s).  The tie to the ignition system is for startup regulator supply only.

Full disclaimer:  I've worked a bit with Ford tachs that are similar to the AMC tachs but not with an AMC tach in particular.


-------------
Roger Gazur
1969 'B' Scheme SC/Rambler
1970 RWB 4-spd Machine
1970 Sonic Silver auto AMX

All project cars.



Posted By: Someassemblyrqd
Date Posted: Jan/25/2019 at 11:52pm
Are you sure that the tach won't withstand 12 VDC to ground?  No, I’m not sure, didn’t have an extra tach to sacrifice.  What I do know is the voltage to the tach is ~9.6v.   The pink resistance wire provides this reduced voltage from the ignition .

What do you think the voltage is at the coil + terminal with the key on, the points open, and the engine not running? ~9.6v.  The pink resistance wire, which connected to the yellow wire at the solenoid.  This yellow wire feed power to the I terminal on the solenoid.  The blue wire connected to the same terminal feeds power to the tach and on to the coil + side.


With regards to the charging system, I per port not to be an expert.  All I can say is I’ve read a lot of Billd’s write ups and he has stated that the exciter wire does not want the full 12v



  


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Greg E.


Posted By: 6PakBee
Date Posted: Jan/26/2019 at 7:43am
Greg,  I fully understand and appreciate your caution in moving forward with your project.  It's hard enough to get 50 year old parts without destroying them due to carelessness or poor choices.  That being said, I think that if you configure your car as I outlined, key on, engine off, points open (or - side of the coil disconnected if you do not have your points distributor) and measure the voltage at the coil + terminal, it will be full battery voltage.  If there is no current through the resistance wire (points open) there will be no voltage drop. 

In the end it may be better to have your tach converted and driven from the tach output on the MSD distributor.  Good luck.  

As to the charging circuit, I stand by my original statement. 


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Roger Gazur
1969 'B' Scheme SC/Rambler
1970 RWB 4-spd Machine
1970 Sonic Silver auto AMX

All project cars.



Posted By: White70JavelinSST
Date Posted: Jan/26/2019 at 8:44am
I took a couple of pictures this morning, probably won't help anyone a lot, but know that the White70JavelinSST is wired like this.

Three wires from the distributor,

Orange wire to negative side of coil
Red to positive side of coil
Black to ground

Yellow wire from 70 Javelin factory in dash tachometer to positive side of coil.

Disconnected the yellow and pink (or on this car it looks tan/light brown but could be color faded) wire from the solenoid, (not used).


The distributor wire connector is ty-wrapped to the oil fill tube. There is no gray wire on this MSD RTR Billet Distributor. The underhood has never been restored on this 50 yr old car. The engine has never been out so please forgive the appearance.

The tach works fine. It has worked fine for probably ten years wired this way.

The two yellow wires wrapped in the factory thermal cover and just to the front of the voltage regultaor go to the starter side post of the solenoid. The black ground wire from the distributor is grounded to the horn relay mount (wire is seen just above the large red cable to the amplifier and between the two SS braided AC lines). The disconnected yellow and tan wire with a blue piece of tape around it can be seen in front of the voltage regulator and a bit below it.

I do not have a MSD ignition box installed nor is there some other type of tachometer adapter being used.
It's just the MSD 8523 RTR Billet Pro-Distributor, Blaster 2 coil and factory AMC 8k tachometer.



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70 Javelin SST, second owner, purchased 1972


Posted By: Bucks AMX
Date Posted: Jan/26/2019 at 9:10am
To solve the issue of can't shut car off go to this link (MSD Tech Support) and click the Engine Run On tab. Follow directions, it worked for me. I have the factory tach as well as an Autometer tach and both are operational with the RTR distributor.
1970AMX

https://www.holley.com/support/troubleshooting_techniques/" rel="nofollow - https://www.holley.com/support/troubleshooting_techniques/



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1970 AMX 390 4spd Golden Lime


Posted By: Someassemblyrqd
Date Posted: Jan/26/2019 at 1:39pm
Roger - agree, good discussion.  With my ‘70 AMX, I wanted to stay with the original wiring and electrical system schematics.   I initially used Armand’s (White70) wiring diagram for my MSD 8523 dist.  because of common wiring - it didn’t work, hard starting, popping, shuddering, etc.    I believe this due to Armond’s dist being 10years older, no grey wire for tach wave signal, which my dist has.  I believe this is why other current 8523  dist owners are experiencing hard start/run issues.

By adding a discreet 12v line to the dist tied into the ignition wire before the pink resistance wire, I accomplished the best of both old and new:  modern 12v dist, integrated into the original ‘70 wiring, no tach upgrade expense.

Thanks. Greg



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Greg E.


Posted By: PHAT69AMX
Date Posted: Jan/26/2019 at 2:14pm
Probably no help, this worked with MSD Box and a UniLite Conversion,
which obviously is different than a Magnetic PickUp, HAL Effect, or HEI



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Link to a http://www.youtube.com/watch?v=MySiKQsmWxU" rel="nofollow - Short YouTube Burnout Video



Posted By: White70JavelinSST
Date Posted: Jan/27/2019 at 10:19am
I purchased a second MSD 8523 about four years ago for use in a fresh build 70 390.

I just opened the box to verify.

It has the grey wire, so I'll be using Someassemblyrqd's wiring method probably.

What I find interesting is the popping and sputtering some one posted about earlier. That almost sounds like a way out of time setting problem. Like 180 degrees out of time.


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70 Javelin SST, second owner, purchased 1972


Posted By: Someassemblyrqd
Date Posted: Jan/27/2019 at 3:16pm
Armand - I’d like to hear from you on  your engine start/run results by you plugging in the new rtr dist in your Javelin with its current wiring.  Would like to see if you different results (runs smooth, no popping/shuddering) or the same as I experienced thus you needing to follow my wiring.

Pls let us know.  Thx. Greg


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Greg E.


Posted By: 092171michael
Date Posted: Jan/27/2019 at 3:17pm
Holy bajesus, it worked!! Someassemblyrqd, thank you so much for the drawing.  And then dumbing down the directions so that I could understand it. I really appreciate it, let me know where to send the check.  Wink The car starts and shuts off, and the tach works.  I tried to spiffy up the wires a bit. Now, only 2 more problems(maybe 3) I didn't know if I should ad on to this thread, or start a new one. So I'll start a new one, it will be titled, ALT Light Still On. Help me if you can. Thanks again.


Posted By: White70JavelinSST
Date Posted: Jan/28/2019 at 3:43pm
Originally posted by Someassemblyrqd Someassemblyrqd wrote:

Armand - I’d like to hear from you on  your engine start/run results by you plugging in the new rtr dist in your Javelin with its current wiring.  Would like to see if you different results (runs smooth, no popping/shuddering) or the same as I experienced thus you needing to follow my wiring.

Pls let us know.  Thx. Greg


Someassemblyrqd,

I'll try to keep that in mind. This is one of those projects that drags on and on cuz so much other stuff gets in the way. Right now the problem is, it's way too cold in my shop.
Anyway the plan is to break in the cam on an engine run stand. So I'll wire it pretty simple, just to start and run. I may try to borrow a suitable tachometer if I can. But I'll try to keep you updated.

Armand


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70 Javelin SST, second owner, purchased 1972



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