76 304 TFI DuraSpark upgrade

76 304 TFI DuraSpark upgrade
Southern Arizona
76 CJ5 304 all stock T-150 D20 4.10 gears
First thing was researching thru articles after articles and deciding on the DuraSpark or the HEI module. I chose the DuraSpark simply because I wanted a clean factory look and I did not want to fabricate a box and heat sink needed for the HEI module. I also like the sealed system of the DuraSpark module. Keep in mind this is a mid level upgrade, and argued the HEI is more appropreate upgrade designed for the use of the e-coil without the need of a resistor wire or resistor pot. My plan is to adventually install the resistor wire and eleminate the resistor pot. This is a complete system designed from scratch spacifically intended to replace the Prestolite ignition system.

I have been running this system for two years and simply love it, it is really nice to know when I turn the key my old Jeep starts!

TeamRush, JunkYardGenius, have some very good in-depth articles on the swaps.

I am more of a picture person, diagrams and drawing don’t always make since to me. I could not find a good picture step by step layout of the project for the V-8, just the I-6. So I will attempt to help out those like me. I also enlisted the help of my good friend Greg Fody.

I could have done the upgrade cheaper but I figured that I am doing this for a reason so I opted for top of the line parts. I bought the distributor from NAPA (79 AMC 304 part #48-4891) since I have never had any luck with other remanufactured distributors. The distributor was about $20.00 more but you get what you pay for.

I got the base, large cap and tall rotor for the distributor from SummitRacing.com as a package (part #MSD-8414) and the MSD 8MM Heli-Core plug wires (part# MSD-3119 ).

The TFI E-Coil was also from NAPA (part# IC24SB) as well as the E-Coil wire adaptor (part # ICC1), Resistor Pot (part #ICR23), Duraspark module (part #TP40SB) and Dielectric Silicone Compound. Pick up some wire separators and wiring loom while you are there. I already had new Autolite plugs so I did not purchase new plugs at this time.

You will need to round up the male wire connectors from a donor vehicle (76-85 Ford truck, car or Jeep 79-?) for the module and distributor. CarQuest did have some aftermarket connectors (part #S-629 & S-698) (note; they may have changed the part #’s to 574603 and 574629) but for a good price.

You will also need to pick up some wire in assorted colors, Black, Red, Red W/Blue tracer, White, Orange, Violet, in 18 gauge, and Green in 16 gauge. Try to pick this up at a shop that will sell it to you by the foot. 3 foot of White and 12 foot of the rest will complete the job as we did it

Now that you have the parts and you have down loaded the wiring diagrams, you can start to make a game plan on where you are going to install the DuraSpark module and E-Coil. Since the E-Coil is not liquid filled, you can mount it in any fashion that suits your needs, even up-side down.

We chose to locate the DuraSpark module next to the Voltage Regulator. This severed several reasons for me. 1) I wanted the space where the old Prestolite module was located for an overflow bottle from the radiator. 2) It made since because the factory wiring harness ran to the Voltage Regulator and the Starter Solenoid, both of which we would be using for the swap. 3) It was at the end of the factory wiring harness so we would not have to splice into the middle of it. Jeep placed the DuraSpark module on the drivers side wheel well.

This was the wiring diagram we came up with (thanks to John Strenk and JunkYardGenius) that was easier for us to understand. It is laid out as if you were standing at the front of the Jeep looking at the engine compartment. The distributor, coil, voltage regulator, and starter solenoid are all in their original locations.

Once we decided on the location for the Durasprk module, it was time to drill the holes. Placing the module on the outside wheel well, we were able to line it up across from the Voltage Regulator and mark the holes to be drilled.

Once the holes were drilled, we were able bolt the module in place.

We decided that the original coil location would work well for the new E-Coil. It was next to the factory wiring harness needed for the tie-in and gave us a short shot for the High Tension Wire (coil wire) to the distributor. We just had to fabricate a housing for it.

We used a piece of flat stock ¼ x 2 x 3 ½ for the bottom plate. We used 2 pieces of 1 inch angle iron 3 ½ inches long for the up-rights to bolt the E-Coil on and welded them in place. We raised the E-coil off the bottom of the mounting plate about ¼ of an inch for air cooling. This gave us a place to bolt on the Resistor Pot also.

Make note that you have very little room if you decide to use the original location. Notice the clearance for the fuel line on the far side and the clearance for the valve cover on the near side.

Now it’s time to get a look at the wiring harness to see what you will be taking off. We pulled off the loom that covers the wires to see if there were any splices from the previous owners. We did not want to place an upgrade on a spliced up mess! Now would be the time to correct any wrong doings. Lucky for us, all the splicing was done on the section we were removing!

Once the wires are exposed, you are looking for one specific factory (3 way) splice that is located in the area of the old coil. You will be keeping the Red W/Black tracer wire going to this splice as well as the Black wire on Jeeps with Ford alternator and voltage regulator. (I am not sure of the color on Jeeps with the GM system.)

Once the factory splice is found, you can start removing the old Prestolite system.

It is a very good idea to have found T.D.C. prior to pulling the old distributor.

Now that the old system has been removed, you can put the new Motorcraft distributor in place. You will need to line up the oil pump slot with the new distributor.

Once the distributor is in place and the cap is on, check for clearance and vacuum advance movement.

Now it’s time install new spark plugs with a gap of 45 (be sure you do not pry down on the plug rod as damage to the plug may happen) and to line out your spark plug wires and cut them to length. (Many use Ford 460 cut to fit prefabed wires with good luck, ours must be fitted) Separate the different lengths of plug wires, and decide what length is going to go to what cylinder. It would be a good idea to keep them a tad long.

I hate making spark plug wires and may try the fitted Ford 460 next time as this was the most time consuming part of the whole process. Be sure to follow the directions to a “T” and use the Dielectric Silicone Compound. We used the Dielectric Silicone on the wire and inside of the boot to slide the boot onto the wire.

Make sure you bend the edge of the wire crimp over 90 deg. To ensure a good crimp!

Once the wires are completed, make sure to install good wire separators such as Moroso and do not leave them bunched up like this.

For the new electrical wiring, we took all the wires in factory color code, Red, Red W/Blue Tracer, Orange, Black Violet and Green (not the White wire) and taped them together as one assembly approximately 10 foot long. (The Red with Blue tracer will be tied in last to the (I) side of the starter solenoid later) This new assembly will run right next to the factory assembly.

The Violet, Orange and Black wires will “Y” off to the distributor.

Once the new wiring assembly is laid into place, it should look something like this.

We started the tie in at the DuraSpark module working backwards. Solder or crimp your new wiring assembly to the new or donor male socket pigtails going to the Duraspark module. Pretty simple stuff following the factory color code, Black to Black, Orange to Orange etc. and connect the new wiring assembly to the module.

The White wire off the module was tied into the Starter Solenoid on the (S) side (power when cranking). The Red wire will go to the Resistor Pot that will tie into power from ignition (Red W/Black tracer). And the Black wire off the module was grounded at the mounting bracket bolt of the Starter Solenoid. Be sure to double check RUN and CRANK on the Starter Solenoid prior to connecting. This can be done with a test light.

The Black wire from the module was not cut in two for the tie in. We pulled slack in the new wire assembly so we could bare approximately ¾ inch where we planned to tie in and crimped on our “eye” connectors.

We then moved over to the distributor side and once again solder or crimp on your new or donor plug for the distributor. Following the color code (Orange Violet and Black from the module) and connect your new pigtail to the distributor socket.

Now we went up to the (3) way factory splice and made a new (3) way splice for our system. At this splice we tied in the factory Black wire (on the Ford system, GM system will have a different color) from the Voltage Regulator. The other side of the new (3) way splice, we tied in the factory Red/W Black tracer wire (power from ignition).

Now we have the Red and Green wires from the module that “Y’s” off from the wires going to the distributor.

The new Red wire from the module will connect into the same side on the Resistor Pot that we ran the red wire from our new 3-way splice. (RED W/BLACK TRACER GOES TO THE 3-WAY SPLICE WITH BLACK WIRE TO THE VOLTAGE REGULATOR, NEW RED WIRE TO THE RESISTOR POT SAME SIDE OF RED WIRE GOING TO MODULE. The Green wire simply goes to the (-) side of the E-Coil.

In the picture below you can see the Resistor Pot with power from the Red W/Black tracer (ignition Source) and our Red wire from the Module on the bottom. (Remember this is powered from the new (3) way splice).


You can see 2 Green wires in the picture below off the connector for the E-Coil. One side is to the module and the other will go to a tach or you can just cap it off.

Double check all your connections following the color code and you are ready to start it up. We set the timing at 10 deg advanced. Place your new wiring assembly in the new wiring loom and you have a very clean factory looking set-up.

This pic is why I placed the module by the voltage regulator. I wanted a clean place to put my overflow bottle I got from Pep-Boys for around $14.00.

Thanks to all that helped me out on this project Team Rush / Junk yard Genius / JeepHammer / Greg Fode

This might be a wiring diagram that works a little better for your application...


Where the 'Red' wire from the Ignition Switch 'Run' Position hits the harness at the first splice,
The 'Excite' wire for the alternator circuit isn't shown, but you get the idea for the Ignition System.


The only problem I have with it is calling it the 'TFI' upgrade,
Since you didn't use the TFI module or distributor.

I used to sell harnesses for just this swap for the guys with breaker points or Prestolite,





Couldn't sell them with the 'Cheap' HEI's on the market out there, even though it was a better way to do things to keep the ignition 'Modular',
So the last of them laid around here until I threw them out.

Too bad actually,
The plugs were marked 'FoMoCo' (Ford Motor Company),
The trigger pair were twisted and shielded from the manufacturer,
And I had them made in the same plant that built for Ford...

They saved a TON of aggravation,
No resistor wire, easier to leave it out and add a ceramic block resistor if you wanted one,
But a LOT less work for the guy that wanted to run a full power ignition,
And I installed the coil plug of your choice,
Horseshoe or E-core,
And I installed the alternator plug of your choice with resistor or diode so there wasn't any back feeding to the system...

I tossed nearly 1,000 of them in the dumpster a while back to make room for some new stuff, this one has been laying out on a shelf for nearly 10 years and survived the purge...

Minimum order was 2,500 and when I broke even on the deal, I simply stopped advertising them...
Prestolite Upgrade to Duraspark Distributor & Modual on Jeep CJ


Way to go on the upgrade of the Prestolite and use of the TEAMRUSH use of upgraded Ford Tune up parts and the Duraspark Modual and Duraspark Distributor..... I did the TeamRush and the Aux Grounds about 5 years ago and make a big difference.

TeamRush / JeepHammer
Thanks so much for valuable time and efforts in making this upgrade path known, educating jeeper far/neer on how to do it properly. U will go to jeeper heaven some day.

few thoughts

The distributor signal wires to fire are produced by the reluctor fins spinning past the coil pick up. Develops small "low level signal", mili volts and milit amps, and needs a bit of signal protection. The low level signal wires from distributor to the duraspark modual, or any igntion modual, should be twisted 2-3 turns per inch. This will cut down cross talk and other noise of Induced Currents from higher voltage & switched wires under the hood. Ignition Power to the coil, spark plug wires, even motor power wire will have magnetic flux lines around them as they turn off/on. EVERY TIME when they turn off/on the flux lines grow and collasp. Twisting means every twist will induce opposite small currents that will cancell each other or help. Keep distributor wires next to fender wall and firewall so the metal ground plane acts like a shield. Keep Distrutor wire from the coil power wires and the spark plug wires.... they are high power and switched many times per min. Add a msd and freq is now 6x the rpm since we fire 6x cylinder and much higher voltage 500v.....so even more important to keep the distributor wirs from the ignition or electric mortor wires

MSD 6 series if you find one on local swap or craigslist for as little as $35 will wire right to what you did. Give you better igntion, the duraspark modual is now a field swap back up. Change connector at distributor so fires MSD rather than Duraspark Modual, use same connector series. Cap off the Duraspark Connector with a film vial & cap & dielectric grease squeezed into conn housing. Undo the aux ground to Duraspark Modual and the D Modual will sit there at idle with NO ground ready to be used again with connector changes. Will also need another set of wires to go from the MSD to coil to fire the coil.

Battery + was pretty oxidized on the far end. Connector up up to collect moisture and oxidize more. Might want to reterminate that one, resolder, and use heatshring/w sealant. That could be lowering your amps to starter a bit.

Aux grounds....
Ignition is DC and power goes out to plugs and will go back to battery. Good GROUNDs will protect your DuraSpark Modual and make your igntiion work better. Ground both your heads with a 12-14 awg wire is a good idea to firewall if you have aux to firewall or directly to battery. I added aux grounds to block, starter, grill, firewall, dash, frame, duraspark modual.

Duraspark can be killed by:
Leaving key on RUN w/o the engine running...... constant power state causes heat build up. Potting compount in Duraspark will melt and run on fender or mtd location. Duraspark Modual is a great little igntion.... has a igntion retard during start up for easy starting. One of the reasons Duraspark has a start and run fuctions.... its for better starts. Also not all Duraspark Distribtors rebuilds will have the larger mechincal limit slots. When you get one look down the cover plate hole the limit slots will be numbered 5R, 8R, 13R, 18R and there are some more that show up at times. WE want the 13r/18r combo if you can find them. The Smaller 5r/8r are on the computer control versions 1982 & newer will not work out well w/o functioning computer and sensors and feedback carb.

Poor ground in will kill duraspark.... another reason we add aux ground

Poor ground circuit at the head or spark plug will also over work DuraSpark and cause a failure

Good Grounds make the system run much better
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Re: Prestolite Upgrade to Duraspark Distributor & Modual on Jeep CJ

Thank you Team Rush and MN CJ7 for the input, alway looking to learn. Team Rush you are correct, it should be just "76 304 DuraSpark upgrade". Too bad you trashed all those harnesses, would have loved to have had one! I'm really glade I did not do a cheap HEI, I always questioned if I would god one that had the wrong gear and trash my motor.

MN CJ7, no I have not twisted the wires, I read something on that on another forum but was unable to find it again. All the ground have since been corrected since the install along with the battery cables. I had them cut back and new ends soldered on. all my ground wires have been replaced with ground cables or straps. TeamRush always beat it into people about good grounds on a Jeep, glad he did. I had thought about the MSD 6 series, I'm just so satisfied right now I hate to fix something thats working great. I will eventually get around to it. Right now I would be happy to find a resistor wire.

Cant say enough about this system, may not be the "best" system but what a hugh difference it has made!

Thanks again for the input and the time to reply! I am learning and with input like you guys have given, it make owning an old CJ more bearable!
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As far as 'Grounds' Go...
Electrically speaking,
You aren't driving a solid vehicle.
Every part is flying in VERY close formation, but no formal electrical contact unless you saw fit to 'Ground' your electrical loads yourself.

When I get a Jeep in here with this or that electrical complaint,
I spend about an hour adding DEDICATED GROUNDS!
Everyone is so amazed how much better the headlights work, the wipers work, the ignition works, tail lights work, ect. when it gets DEDICATED GROUNDS!

If you get the power INTO a load or device, it only makes sense to put a solid path in for the circuit to complete!


As for the Ignition, you now have a MODULAR ignition,
You can swap, change, upgrade as new and more powerful this or that comes along without starting over.

For about 90% of the guys, just getting a reasonable cap, rotor, plug wires on the vehicle makes a HUGE difference,
And it sure beats trying to GUESS if the $100 HEI clone you got off E-bay has a correct length housing, correct gear, the guy putting it together took time to tune it, or it has the correct coil, screws, center button, ect. that will keep it alive over time.

What I'm seeing more and more of is 'Red Dust' under the rotors on the 'Internet' HEIs that came with plug wires.
High resistance plug wires cook the :dung: out of the rotor, cause all kinds of ionization problmes,

If you have 'Red Dust' under the rotor, and 'Black Dust' on top the rotor,
The cheap, high resistance plug wires are causing the spark energy to blow though or around the rotor,
And they are blowing the center terminal 'Button' apart to make the 'Black Dust' on top the rotor.

That carbon is conductive, so it's a freeway for even more of the spark energy to get at the advance weights in an HEI...

Nothing beats a good set of low resistance plug wires, No matter what ignition you are running!

The MSD (not 'Street Fire') wires work really well with HEI since they are low Impedance also,
You don't loose NEARLY as much spark energy on the way to to the wire as you do with High Resistance/High Impedance plug wires.
Some of the cheap, off the shelf wires from the parts stores will loose up to 75% of the spark energy on the way to the plug!
That's just unacceptable...

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