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Discussion Starter · #1 ·
My MSD is acting up over 5000 rpm, so I am looking for a replacement.

My rev. limit is only 6500 with the stroker

I have read numerous posts that a MSD style ignition does not make any real power when compared to a stock Duraspark when tested on a dyno?

But the factory Ford ignition modules are not the best in terms of dwell time and spark energy.

I just read an article about using a factory Dodge ignition module with the Duraspark distributor. The Dodge igition module supposedly gives a good long powerfull spark.


Anyone done this?
 

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The factory Duraspark 2 module runs 26 deg of dwell.
I switched to a Jacobs FC1000 ,and it is advertised to run 20 deg of dwell, but my car runs great.
I also got the Ultra Coil to go with it. When it is running, I can lift a boot off the dist, and see all 6 sparks jumping the gap (pretty cool looking).
The Ultra Coil is one mean coil, it can be adapted to and OEM or aftermarket, I'm just glad I haven't got "bitten" by a spark(yet)
. 6 nice BLUE sparks, at a max of 60,000v might sting a little. I got my system on ebay used, the FC1000 and Ultra Coil, for less than $100 shipped.
Maybe you can get a good Duraspark 2 module and get an Ultra Coil, that way you can get 26 deg of dwell and get a hot spark at the same time. Even if you already have a CD ignition, you can adapt this coil.
Sorry to sound biased, but if I find something that works for me, I like to spread the word.
Just a thought, good luck, Chris.
 

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"When it is running, I can lift a boot off the dist, and see all 6 sparks jumping the gap (pretty cool looking). "

"I'm just glad I haven't got "bitten" by a spark(yet)"

Well, if you intentionally like to take off the boot from the coil off the distributor to watch the sparks jump the distance, if you keep that up I can pretty much promise you that you will get bitten, but by bitten I mean you might kill yourself.

I accidentally, not intentionally, bumped the coil wire off of my MSD distributor while the motor was running once, and between the Blaster 2 coil and my 6AL box, the "bite" threw me 4 feet straight back against a wall and my heart beat irregularly for the next hour and I felt like I was going to vomit the whole time.

In other words, be fu**ing careful.
 

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No but seriously, my T-bird computer was acting up and I was trying to see if I had a weak spark, injector problem, or computer. Swapped it out for an a9l mustang computer and the problem was gone.
I always use a pair of plastic plug boot pliers. I learned my lesson accidentally a couple years ago by setting the timing on my car, using a non-inductive timing light . Even with Duraspark 2 and a TFI coil, that felt like somebody punched me in the chest and my left arm was numb for a while.
I now have all inductuve timing lights, MOROSO Ultra 40's, and full Jacobs Ignition along with my EFI conversion and couldn't be happier.
Chris.
 

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A friend of mine was dead for 9 minutes.....we were trying to isolate a miss on a SBC sprint car (magneto style ignition) and he pulled a wire off. Pronounced dead at the scene by the EMTs...but they managed to revive him.

How he survived the whole deal is a mystery.

I did the same thing with my Maverick. Pulled a wire off and got hit hard. Heart stopped for a minute or so, left side was numb for a while. I spent the rest of the day relaxing in the ez-chair trackside rather than racing. I didn't feel comfortable going 130+ in that condition. Just as it was described previously, it feels like you get punched in the chest, then the numbness in one or more body parts (usually on the left side) and sometimes paralysis.

don't fool around with "juice". it's shocking in what it can do to the body.
 

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stand in water? j/k
how do you unground yourself? is it ok to mig without gloves? i do it alot.

i am lucky as i have said crank it while checking each plug/wire for arc. and setting timing while motor is running.
 

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you thought right.
has anyone tested it? i searched for certain key words and found nothing. whered you hear this from buddy?
 

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jeffstar-
Yup. I've run the Chrysler (LX101) module and triggered it with the
Duraspark distributor. One of my friends who runs a private race
shop uses that setup frequently on some of the customer's street
vehicles. I've got the wiring diagram in my desk at home.
It provides better performance than the Motorcraft module but it
isn't normally used for full race stuff. I'd say 6500 might be the
max upper limit.
 

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That badass cars site needs to do more research. So far, each article I have read was full of errors, omissions, and flat out bad information!

Greg
 

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You can use the Mopar (or any other) power modules. It does not matter. All you're trying to do is A) enhance the current limit on the DS to B) allow running a different coil that the one specifically for the DS. If you run the proper DS coil, performance will be fine, as the DS coils have a very low resistance and moderate impedance just for the DS system. Using a coil with higher resistance or impedance (common mistake) will give a weaker spark as you are still limited by the DS dwell. Using a coil with lower resistance or impedance will give a hotter spark if you use another module to allow greater current (power) to the coil.

Recap of the basics so you know what you're trying to do: To increase spark energy with a DS system, you must allow for greater power flow. Since the dwell (coil charging time) is fixed by the DS box, the only way is to reduce the coil resistance, coil impedance, or both. So you replace the coil with a HP one. Cool. Problem now is the greater current needed to fire the new coil hotter is limited by the DS. So, we add a power module to increase the power flow (current) capability. Bingo. Hotter spark.

So, use whatever module you like, as long as it can handle more current than the DS box. The Mopar modules are fine as they are 'dumb' (not capable of dwell control) and just allow more current. So are a bunch of others, like the GM 4-pin (although limited to about 7.5 amps), or even my favorite - the J701 "Power Unit" used on Mazdas, Kias, Mitsubishis, Fords, Mercurys, Subarus, etc. This little sucker is really small (using more modern technology compared to the Mopar box), and can handle enough power to arc weld with. Well, almost. I haven't been able to burn one up and don't know anyone that has. Wiring scheme is the same as the Dodge/Mopar box. Be sure to mount it on a flat metal surface for cooling.

David

The J701 single coil power unit. As you can see it's small in my small hand, and the connector is actually bulkier than the module itself. Grab the little box capacitor that is mounted by it for best spark and RF/EMI (radio static) suppression.


 

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my favorite - the J701 "Power Unit" used on Mazdas, Kias, Mitsubishis, Fords, Mercurys, Subarus, etc. This little sucker is really small (using more modern technology compared to the Mopar box), and can handle enough power to arc weld with.

The J701 single coil power unit. As you can see it's small in my small hand, and the connector is actually bulkier than the module itself. Grab the little box capacitor that is mounted by it for best spark and RF/EMI (radio static) suppression.


David, I found one your old post.

Just wondering if J701 can be used with Duraspark Distributors. These are only couple of bucks at my local pic-a-part. Just like HEI, this also does not have dwell control (coil charging time). Right?

Looks like much better package than the HEI with exposed terminals.

Thanks


Waid
 

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Just wondering if J701 can be used with Duraspark Distributors. These are only couple of bucks at my local pic-a-part. Just like HEI, this also does not have dwell control (coil charging time). Right?
Right - no dwell control, but also no other current control, so the answer is "almost". The J701 is designed to be controlled by dwell to limit current to the coil. Grab a cup of coffee.

To get maximum spark energy, you need to saturate the coil with enough current, long enough, for it to reach full voltage. At full-saturation, you have maximum spark voltage and amperage available. At less than full-saturation, you get a weaker spark. At more than full saturation you generate nothing but heat in the coil and ignition system. So, for best spark performance without cooking parts, we want the perfect amount of energy into the coil, no matter what the RPM.

There are two common methods used to control the current to the coil - dwell time and resistance. Variable dwell control is the ultimate way to do it, but requires computing power to calculate when to start charging the coil so that it has had the perfect dwell time to saturate the coil before we shut off current to fire the coil - at any RPM.

If you have no variable dwell control, such as points or most electronic modules, you have to control the current with resistance to prevent cooking parts under the worst conditions - low or no RPM.

Take points as an example - the points open and close the same number of crank degrees every time. When you add time to the mix, you get too much dwell at low or no RPM, and too little at high RPM. Too little dwell means a weak or no spark, but too much means you're cooking your coil. So, Ford added the famous pink resistor wire (and MOPAR added the "ballast resistor") to reduce the current through the coil to limit the heat, especially if the engine stalled with the key ON and coil power flowing. The combination of fixed dwell and fixed resistance works fine at lower RPM, and it's enough to run the engine through small plug gaps, though it also reduces spark energy as RPM rises with less dwell time to saturate the coil. That's right where performance people want a better spark - not a weaker one.

Jump forward to electronic modules. We still have fixed dwell, but now modules such as the GM 4-pin use variable resistance within the module to limit the current flowing if dwell is too long (current limiting), instead of a fixed resistance wire or ballast. As RPM increases and dwell time becomes shorter, the module uses less current limiting so spark remains strong. The only down-side is the module gets hotter the more it has to limit current. The best up-side is that current limiting allows coils with much lower primary resistance and higher energy capacity to be used - HEI.

By the time distributors are becoming obsolete, ECMs begin to control the ignition, using their computing power to vary the dwell time. This produces far less heat as there is no current-limiting resistance - just on and off at the right time. Everything runs cooler even with very high-energy coils, and performance us much improved with high energy at all RPM and large plug gaps to fire dirty, very rich or very lean mixtures. This kind of control in a stand-alone distributor module is very rare. The Ford DuraSpark-I "red-grommet" module is one of them, using a combination of variable current limiting and variable dwell to reduce heat. This is why it was so expensive in the day, and why it was only used as-necessary.

What about he J701? Yes, it could be used. If you digested all the basic requirements as outlined above, the distributor has no dwell control, and the J701 has no current limiting. This means the J701 can be used for ignition but must use coil resistance like the old points systems did, and the OP's MOPAR module requires, with the same limitations. In this way it makes for a really small and cheap alternative to a PerTronix I. However, it really shines if used with dwell control as it was intended. In this way, it can be added to an existing control system to increase the power handling for higher energy as I stated in the 2nd paragraph of my last post. The little J701 is also really handy for use with multiple HE coils and dwell control, which is how I use them.

I hope this rough overview helps understanding of ignition requirements overall. While not that complicated, there are a number of rules that must be understood and followed for best performance, and limited ways that 'work-arounds' can be used to bend those rules successfully and with minimum compromise and maximum reliability. Hope that helps.

David
 

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David,

As soon as I got home, I went up in my attic and found my TBI box and found computer controlled distributor, a spare 8 pin HEI modules and a HEI coil. I also found the wires/pig tails too. While I agree with you that the Red Grommet is the best choice, I already have these components which I was going to pitch. I will have one HEI module in the engine bay and one spare in the glove box !

As per my PM to you, I found this link below.

Troubled Child: GM TBI Ignition Wiring

Do you see any issue with the way its wired ?

Waid
 

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The schematic labeled TBI_Wiring_1.jpg (4 of 6) looks fine. Use the HEI coil that is with it. Be sure you mount the module on a substantial heat sink (preferably aluminum) off the engine if possible (firewall or apron?) with heat sink compound. Both internal and external heat kills them. Be sure the BLK distributor wire is well grounded to the module and heat sink, and all that is well grounded to the chassis, and the chassis well grounded to the block and then to the battery (-).

The 8-pin module was designed to use dwell control, though it has a protective current-limiter built-in. When running it for the first time and before the engine heat-soaks the parts, check both the module and the coil for excess heat. If either is too hot to keep your finger on for 3 seconds or more - it won't last long. If both are cooler than that, then enjoy the ride.

David
 

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That is good to know that the 8-pin HEI has dwell controll too. Guess this would make it as good as the Red Gromet Duraspark?

Found more info on the GM HEI 7 & 8 pin HEI Module here.

General Motors 7-pin HEI Ignition Control

In the GM 7/8-pin HEI, the module converts the AC signal from the variable reluctor pick-up {on pins P & N} in the distributor to a 'square wave' tach signal {on pin R} suitable for MegaSquirt-II. The falling edge of this square wave is used as the trigger event (which becomes the rising edge when the optoisolator inverts the signal).


HEI does not use the reluctor for dwell control, this is accomplished in the module. Dwell needs to be independent of RPM. Variable reluctor output is RPM dependent with regard to both its width and amplitude of its output. The only thing constant with a variable reluctor output is the location of the zero crossing point with respect to the passing tooth.
Be sure to get the variable reluctor pick-up wires connected properly. Reversing the variable reluctor sensor wires and thus the polarity of the sensor causes the leading voltage to go negative first and the electronics ignores the positive going transition. Thus trigger signal, if ever recognized, is the falling edge of the voltage as the end of the tooth passes.

Waid
 
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