1974 Brain Box saves the day.

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Here is the factory 4 pin ballast resistor with the 5 pin mopar style brain box as set up originally.

I bought this truck from the original owners, all original so I know it had not been changed.

Is this the proper setup for 1976, 4 pin ballast resistor with 5 pin Brain Box?

The top of that 4 pin ballast resistor gets hot and the bottom of it stays cool. Guess that is the way it is supposed to work creating resistance so it goes easier on the coil while running.

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This is the way it was wired when I bought it and had the 5 pin '76 brain box on it.

Here is another 4 post ballast resistor running with the 5 pin brain box on the "Run Panel" for the engine run stand.

It runs the engines fine. Does this layout look correct, resistor coil or not . . etc ?

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Have always been under the impression that the 5 pin brain boxes use the 4 post ballast resistors.

Thinking that you can use a 4 pin brain box on a 5 pin harness plug, (but not the 5 pin brain box on the 4 pin harness plug . . don't know here) but then do you need to switch to a 2 post ballast resistor, or just keep using the 4 post ballast and all is fine ??
 
The 4 pin is the universal. Dont need the 5 th pin even with the dual ballast resistor as long as the 4th pin goes to the .5ohm side and not the 5 ohm side. The 5th pin is only another 12v feed in the run position through a beefy 5ohm resistor. Not sure what the reason for this is. It may be a non interrupted power feed to ecu between start and run positions.
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I built a mount like post 80 for mine, but I added a trough at the bottom.

Instead of a step design, I used 1/4" spacers to come out from the firewall.

It has already saved the fresh paint on my firewall by catching a bit of goo that oozed out of the ECM.

My mount also uses the factory ECM mount points, not a wider pattern like the E body/post 80 mount.



On another note- I have a working, vintage ECM that lost it's goo (potting) sitting on the shelf.

Can I just seal it against moisture with anything or are there special requirements?

It has been my experience that once most of the goo comes out the ECM is not long for the world.
 
Well picked up 20 of these, this never happens all of them tested good. usually 3 of ten are bad.
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Well picked up 20 of these, this never happens all of them tested good. usually 3 of ten are bad.
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Awesome A #1
Those are the Best style ECUs with the correct Transistor and Heat Sink setup
And Stamped "Made in USA" in the Chrome Case !
4 Pin ECU

The Premium Ignition Module lifetime warranty brand
(am sure the warranty is no longer valid after that much time being NOS)
Good Units, heck yeah I would run those.

@halifaxhops for the fun of it PM me with a ball park price of what you would like to get out of a single ECU. Thanks

Good For You

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Was just going to list them 45 with the ride is about the least I can do. I like them did them hot and cold (in the freezer for a bit) So good units, that's when I usually see fails like high Rpm or excessive dwell is when they are below freezing.
 
Was just going to list them 45 with the ride is about the least I can do. I like them did them hot and cold (in the freezer for a bit) So good units, that's when I usually see fails like high Rpm or excessive dwell is when they are below freezing.

Not to turn this into a for sale thread. But heck yeah I will take one.
I will PM you to make arrangements.

Thanks

George Jets
 
Had my power supply open the other day forgot about mounting transistors like this would work in a ecu I bet.
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Had my power supply open the other day forgot about mounting transistors like this would work in a ecu I bet.
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Wow now that is really cool.

The unique thing about aluminum heat sinks is that they really pull the heat out. Heat travels to Lesser Heat, always.

You can take a foot long piece of aluminum stock say 2" wide x 1/4" thick heat one end with a torch and the other end ends up being just as hot as the torched end. Heat really moves through aluminum fast.

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OK just to ressurect this. I am seriously thinking about making a tester to check the real point that mopar ecu's break up. Ok spin them up on the distrib machine and use a full system, coil, wires plugs etc. Any ideas? Think it would be useful also to measure the temperatures of the boxes.
 
OK just to ressurect this. I am seriously thinking about making a tester to check the real point that mopar ecu's break up. Ok spin them up on the distrib machine and use a full system, coil, wires plugs etc. Any ideas? Think it would be useful also to measure the temperatures of the boxes.

How about leaving the Key On (ignition switch powered on) for 3 hours without starting the engine. See if that heats up the ECU and takes it out ??

Just a thought of getting it to the breaking point.

This heats the hell out of ignition coils too like in the points distributor systems.
 
How about leaving the Key On (ignition switch powered on) for 3 hours without starting the engine. See if that heats up the ECU and takes it out ??

Just a thought of getting it to the breaking point.

This heats the hell out of ignition coils too like in the points distributor systems.

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Its a start need to mount plugs on some tapped angle iron.
 
Just read through the post. Transistors were as good as it got back in the 1970's. I designed a small engine ignition controller about a year and a half ago using an IGBT instead of transistor. In fact, it (GB14C40L) is specifically designed to drive ignition coils. The ballast resistor helps compensate for dwell exceeding the inductive saturation point of the coil; when it becomes a dead short. I used a PIC microprocessor to control a fixed dwell. I pulsed the coil on the bench measured the time constant with a scope (2.1 ms). Converting a mag-style signal (like Chrysler electronic distributors generate) to a usable digital signal was done with a Maxim MAX9924 VR Signal conditioner.

Believe it or not, one of the major causes of any controller to fail is old capacitors. Even the '90s era Mopars have ECUs failing due to dead capacitors (I've replaced a few). It's possible that when the cap fails, it takes other components with it; parts it was protecting when it was working.

Someone mentioned designing a replacement for the old Mopar Electronic Ignition Controllers. I would probably use the new Silicon Carbide (SiC) type IGBTs, as they have stupid low internal resistance. This means they generate very little heat! They switch in 2-3 nano seconds, and start at about 650 volt ratings and go up from there. Spend a few more bucks and use Gallium Nitrate (GaN, better than even SiC) switches.

When you look at what the OEMs are doing to fire coils (and even injectors), it's worlds apart from the '70s Gold Standard.
 
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When you look at what the OEMs are doing to fire coils (and even injectors), it's worlds apart from the '70s Gold Standard.
Much info on the megasquirt site. Modern ignitions use crankshaft pickups. Some have installed a 36-1 tooth wheel to their crankshaft to trigger a Ford EDIS box. I put one on my 1965 273 engine for the future. Many posts here on using an 8-pin GM HEI module. It controls dwell, so doesn't need a ballast resistor, and can give a stronger spark than Mopar's ECU using an e-core coil. You can just use GM's coil with their cable connecting the two.
 
I Got the home made ecu/phasing checker done yesterday. Pretty cool I set the plugs up to spark 1-8 instead of the firing order it is cool like a sequential strobe when it fires. Much easier to see a fail. Easy to change back to the firing order just wires. Tell you what played with two cheap ecu's and they start breaking up at 4K. This should be interesting to see what the differences really are between them all.
 
OK NOS Just stored badly. Even Mopar used sand in them in the first layer. Checked fine so potting is in order if I can get it halfway cleaned up.
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OK NOS Just stored badly. Even Mopar used sand in them in the first layer. Checked fine so potting is in order if I can get it halfway cleaned up.
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I had another one Rocket sold me that looked they same way , I guess the earlier models that didn't have that process perfected like the later models which have a black rubbery substance in them !!!!
I can just put clear silicone in there and should be fine just dump that stuff out I will address it before storing im sure it still functions properly .
 
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