hei type distributor 73 340 duster

[beerboy]

i am thinking of going to a hei type distrbutor setup in my 73 340 duster, i am seeing that you eliminate the coil , ballast resistor , and ecu box. first is this a smart move? second MSD units are on the high $$ side . i see proform has unit for around $235. can use the plug wires i have now? they do work fine, also would i need a spark box like MSD street fire unit? i have heard the proform unit 67040 which is what i am looking at is larger then the stock unit i am using now. car is not being raced at all, just seeing if anyone else is using this set up and if they like it, thanks for any info. forgot to ask not sure if this unit will have clearance problems with fire wall and so on. the MSD units cap looks more like the stock size

 

[Mattax]

first is this a smart move?

In my opinion. No.
There is no advantage inherent in HEI that will outweigh having the correct timing curve.
Good HEI has the potential advantage of being able to continue providing spark energy, which is really only helpful if the kernal of flame around the spark tip doesn't grow as it should.

can use the plug wires i have now? they do work fine

Depends on the cap that comes with the new distributor.

also would i need a spark box like MSD street fire unit?

?? No. The GM HEI distributors were designed to have that function built into the module which was included with the distributor. You answered that yourself here

eliminate..., and ecu box

i have heard the proform unit 67040 which is what i am looking at is larger then the stock unit i am using now.

If its larger than factory and going on a small block, you know that there is limited room to begin with. Maybe a little better with later firewalls but always tight.

There's even cheaper versions on the market. Not only do they provide the wrong timing curve, but they self destruct. ;)
racingfuelsystems-cheap HEI distributors


Seriously. Do yourself a favor and save your money. If something needs fixing, then fix it. If you want to do a little performance tuning, make one small change and test it out under every condition it needs to perform. Then do another, keeping notes.

'73 Came with the OSAC. If that's not been bypassed, then do yourself a favor and bypass it and there will be a lot better part throttle response.

 

[RustyRatRod]

You may run into clearance issues at the firewall, as the HEI cap is much larger.

 

[67Dart273]

Not to mention it makes the damn thing look like a GM

Having said that, some of us run HEI MODULES, triggered by a factory Mopar breakerless distributor.

 

[Bewy]

HEI is a great upgrade. It has NUMEROUS advantages over the Chrys elec ign:
- 0.060" plug gaps.
- big 5" cap, less chance of spark scatter
- variable dwell. Coil runs cooler at low rpms for more power
- E core is much more efficient
- less exposed connections that can come loose or corrode.
You can also run just the HEI module with the Chrys elec dist.
I can buy Chinese HEI dists here for a Chev for $80, $100 for other brands. I have used heaps of them for over 20 yrs, never had a problem.

 

[MadScientistMat]

A stock Chrysler electronic distributor will wire right up to a GM HEI module, so don't bother with swapping the distributor. If you want HEI, just get the module (and, optionally, a HEI type remote coil) and wire it up. As Mattax noted, having the right advance curve is going to be more important than what module you run. The coil in cap feature on some HEI distributors is slick packaging but has no reliability benefits and a more limited coil selection.

This thread is likely to bring out a swarm of HEI fans and haters. Both can work well with quality parts for most builds. But I will say that outright swapping distributors to get HEI is a waste of money; the original Mopar distributor will run fine.

 

[Mattax]

@beerboy It seems to me you've had a number of threads related to the electrical system on this '73 Duster. For your sanity and ours it will be really helpful to figure out what's been done to this car.
Then instead of trying to explain all of the possiblies, options, and theory, we can zero in on what is there.

B

Thread 'starting help'

May 14, 2021

just was out getting my 1973 duster ready for spring car been sitting for the winter. put batter, y in that was on a tender get in and turn key ---nothing no sounds at all . lights work , radio battery is good. everything worked fine before car was put away. replaced ballast. stiill nothing at the key. cannot understand what it could be never has happened before after winter storage. starter shot, ignition switch bad?? any ideas ? thanks

• beerboy

B

Post in thread 'ballast resistor problem'

Sep 3, 2025

correct resistor and correct ecu box, still testing things. sorry about not giving make and model

• beerboy

B

Thread 'ammeter needle flucuating / erratic bouncing 73 duster'

Aug 18, 2025

tech ?? here my 73 duster 340 ammeter gauge needle moves around from full 18 then back to 14.2 after car runs a bit needle hangs around 14.2 same with my after market volt gauge, battery is pretty new . fusible link is good , no heat issues around bulkhead. could it be alternaor going ? orange box regulator? u tube tells alot of guys to by pass ammeter, whch i get mixed answers with the more electrical type pros say as long as its the stock bulkhead and there are not a ton of add ons dont mess with a bypass.it probably isnt the gauge if the volt gauge is doing the same exact thing, this...

• beerboy
• Replies: 6
• Forum: Electrical and Ignition

A couple tips.
>Photos help. People here can point out where items have been changed, or altered, or ask questions about what they see in the wire routing etc.
>When troubleshooting, posting that something is 'good' or 'correct' doesn't tell us anything technically. For example if its resistance measurement, then people need to know it measured 0.7 Ohms.

One last comment.
The ammeter in your car should not measure Volts. If its says volts on it, then someone converted it to a voltmeter. Ammeters measure current flow. In other words, electrons moving. The flow of electrons is measured in amperes (amps). The original ammeter showed how much current, if any, is flowing into or out of the battery.
There are people on the internet who encourage modification of the battery feed, and conversion of the ammeter to a voltmeter. This can introduce problems especially if executed poorly.
If this was done to your car then it will be very important to see what was done, and how it was done. Again photos will help people here help you.

 

[beerboy]

car is mostly stock units: only non stock items are edelbrock carb, headers , ammeter is stock . the guys i talked to at car shows say hei units are more reliable due to less things to go wrong. this car has no crazy add ons and like i say basically a stock 73 340 duster.

 

[Mattax]

ammeter is stock .

73 duster 340 ammeter gauge needle moves around from full 18 then back to 14.2 after car runs a bit needle hangs around 14.2 same with my after market volt gauge

OK. The above post is what caused the confusion. The ammeter shows -40 Amps (Discharging) to +40 Amps (Charging) of the battery. Current is electrons flowing.

Your voltmeter will show difference of energy to ground at whatever location its wired into.

Some of the equipment looks factory stock but the wiring has been altered.
Alternator has a tag, as did factory alternators starting in '74. We can dig into that more later. Maybe a late build, maybe someone replaced. A '73 Duster 340 came standard with a '41 amp' alternator. dealer data book

What does the red wire visible behind the alternator connect to?

In the next photo we see the cable wrap has been replaced with split wire loom, its no longer supported by the cable clamp (yellow arrow) and the ignition wiring looks to have two pink-red wires at the ballast resistor. Maybe a repair or modification ???

There could be a blue wire on the left and a pair of brown wires on the right connected to the 0.5 ohm resistor. One brown wire comes from the ignition switch for starting and the other goes to the coil positive.
On the other resistor there should be a wire connecting back to the blue wire, and paired with it a wire to power the ECU (blue and yellow in the diagram below). On the other end of the 5 ohm resistor should be a second wire connecting to the ECU (red and green in the diagram). This is needed for the original ECU.

If its a repair, and done well, that's fine. if the wiring is mixed up or new junctions poorly made, that could be a source of problems


In this photo it looks like a heavy brown wire going to the coil, hopefully the positive side. That should be one of the pair of brown 14 gage wires connecting at the 1/2 ohm ballast resistor.

On the other coil terminal looks to be a black wire and a green wire with a parts store crimp terminal. I'm guessing the green wire is for a tach and the black wire goes to the ECU (it may have a yellow trace).
The engine connector in the background is vulnerable to heat and water damage. It is well worth checking the condition.


Not sure what the orange wires are in this photo. The one under the right side of the distributor might be the magnetic pickup from the distributor. The two to the left of th edistributor are the ones I don't know

 

[Newbomb Turk]

car is mostly stock units: only non stock items are edelbrock carb, headers , ammeter is stock . the guys i talked to at car shows say hei units are more reliable due to less things to go wrong. this car has no crazy add ons and like i say basically a stock 73 340 duster.

View attachment 1716452127

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See post 2 and BELIEVE it.

Ignore the rest.

 

[beerboy]

See post 2 and BELIEVE it.

Ignore the rest.

yea thats kind of what i thought go with what i have. you just saved me a bunch of $$ . i was listening to the mopar know it alls at car shows

 

[beerboy]

OK. The above post is what caused the confusion. The ammeter shows -40 Amps (Discharging) to +40 Amps (Charging) of the battery. Current is electrons flowing.
View attachment 1716452143
Your voltmeter will show difference of energy to ground at whatever location its wired into.

Some of the equipment looks factory stock but the wiring has been altered.
Alternator has a tag, as did factory alternators starting in '74. We can dig into that more later. Maybe a late build, maybe someone replaced. A '73 Duster 340 came standard with a '41 amp' alternator. dealer data book

What is does the red wire visible behind the alternator connect to?

In the next photo we see the cable wrap has been replaced with split wire loom, its no longer supported by the cable clamp (yellow arrow) and the ignition wiring looks to have two pink-red wires at the ballast resistor. Maybe a repair or modification ???
View attachment 1716452154

There could be a blue wire on the left and a pair of brown wires on the right connected to the 0.5 ohm resistor. One brown wire comes from the ignition switch for starting and the other goes to the coil positive.
On the other resistor there should be a wire connecting back to the blue wire, and paired with it a wire to power the ECU (blue and yellow in the diagram below). On the other end of the 5 ohm resistor should be a second wire connecting to the ECU (red and green in the diagram). This is needed for the original ECU.
View attachment 1716452173
If its a repair, and done well, that's fine. if the wiring is mixed up or new junctions poorly made, that could be a source of problems


In this photo it looks like a heavy brown wire going to the coil, hopefully the positive side. That should be one of the pair of brown 14 gage wires connecting at the 1/2 ohm ballast resistor.
View attachment 1716452181
On the other coil terminal looks to be a black wire and a green wire with a parts store crimp terminal. I'm guessing the green wire is for a tach and the black wire goes to the ECU (it may have a yellow trace).
The engine connector in the background is vulnerable to heat and water damage. It is well worth checking the condition.


Not sure what the orange wires are in this photo. The one under the right side of the distributor might be the magnetic pickup from the distributor. The two to the left of th edistributor are the ones I don't know
View attachment 1716452185

View attachment 1716452159

thanks for the good info!!

 

[RustyRatRod]

car is mostly stock units: only non stock items are edelbrock carb, headers , ammeter is stock . the guys i talked to at car shows say hei units are more reliable due to less things to go wrong. this car has no crazy add ons and like i say basically a stock 73 340 duster.

View attachment 1716452127

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View attachment 1716452131

If it's running good, why change it?

 

[beerboy]

If it's running good, why change it?

i agree totally thanks

 

[RustyRatRod]

i agree totally thanks

It's easy to get caught up in the hype about "what's better" when the truth is, the Mopar system is purdy dang good. It's only real downfall is the lack of quality parts, but you can find them if you look hard enough.

 

[Newbomb Turk]

It's easy to get caught up in the hype about "what's better" when the truth is, the Mopar system is purdy dang good. It's only real downfall is the lack of quality parts, but you can find them if you look hard enough.

Getting the curve correct is FAR more important than any of this other jabberwocky.

And I’ll say with points you don’t have to worry about slew rate. You just have to control point bounce or float which is the analog equivalent to slew rate.

 

[RustyRatRod]

Getting the curve correct is FAR more important than any of this other jabberwocky.

And I’ll say with points you don’t have to worry about slew rate. You just have to control point bounce or float which is the analog equivalent to slew rate.

Yes. I still have the hot curved points distributor hoppy built up for me. It ran great. The ONLY reason I swapped to the electronic ignition was because I had everything to do it and I wanted to see if there was a difference. The only small difference I noticed was that it starts a little easier and that's all.