Ballast Resistors and Mopar Electronic Ignition Conversions...

moparedtn

Ed on the Ridge
FBBO Gold Member
Local time
3:21 PM
Joined
May 14, 2011
Messages
15,396
Reaction score
26,819
Location
On the Ridge, TN
Some of you will remember the conversion kits Mopar sold under Direct Connection
(and later, Mopar Performance) that included everything needed to convert a points
type ignition to Chrysler electronic ignition.
The kits typically included a new distributor, ECU control unit, a ballast resistor and the required wiring harness.
This was easy to do because Chrysler intentionally used as much of the points type
distributor design as possible in going electronic, so much so that the rotor and caps
worked fine on either and were interchangeable.
The instructions that came with the kit were simple but in typical DC fashion were VERY complete and totally useful in not only installing the kit, but tuning afterwards.
I keep a copy of those instructions to this day.

They even offered (and still do) a "conversion" electronic voltage regulator that uses
the factory wiring to replace the old points type units too, as a constant voltage benefits electronic ignition properly operating.

I've most always converted whatever car I had to electronic using those kits because they just plain worked, were simple to reverse later if desired, and all my cars were street cars
with something resembling stock engines.
Never had a worry about doing so. Parts (if rarely needed) were simple and cheap.
The Accel heavy cap that closely resembles the factory distributor cap even works on either type factory distributor also, as does their rotors and I use both.

All that said, on to the point of my post:
The GTX I have now came with a manner of electronic ignition conversion already done.
They didn't use the ballast provided in such a kit, instead cobbling some sort of "double" ballast off of some later Mopar in the stock location (it appeared they ripped that harness, the ballast and some generic control unit out of a mid-70's model of some sort).
I corrected all that to the "proper" harness and installed a control unit I had in my stash,
the typical "orange box" Mopar unit included in the kits as well.
For an ignition coil, I currently have the popular "Blaster II" unit from MSD, connected by stock harness.

Well, Ed got to thinking too much a while back....
In an effort to get maximum spark to the plugs, I got to thinking that since the Blaster II doesn't require an external resistor when used with electronic ignition, I'd replace the stock ballast resistor (or even eliminate it).
I experimented with different rated ballast resistors, took a bunch of meter readings at the coil for voltage reaching it, all that "thinking too much" stuff.
Currently, I have a ballast that is rated to damn near nothing (like 0.4 ohms) on the car, trying to get the full 12VDC through the system.
In the end, I don't think it made that much difference either way.
BUT....
Have I negligently caused possible harm (or at the least, messed with) the function of any OTHER parts of the ignition system in doing so?
What about the Mopar ECU? Does it matter what voltage gets to it?
Anything inside the stock distributor affected by what I've done?

Reason I ask is I'm chasing down a slight "jittery" run condition under very light load, low RPM conditions (say, going down main street at 30mph at like 1700RPM) where the engine can be felt just ever so slightly doing a little jittery "dance".
(The same situation can be almost imperceptibly observed sitting still and revving the engine gently above 1500RPM or so, up over 2000RPM). There's tiny little half-assed jitters going on.
NOT actual misfires or anything like that and the condition can be quickly overcome with more throttle and/or load applied; further, when the car is accelerated, there's no issues and all functions like it should.

Am I chasing after minutiae here? Does the ballast have anything to do with this?
Does anyone know what the rating of the ballast resistor sold in the Mopar conversion kits was/is?
 

Nacho-RT74

FBBO Gold Member
FBBO Gold Member
Local time
9:21 PM
Joined
Oct 8, 2012
Messages
5,713
Reaction score
2,220
Location
Valencia, España
actually I read from MSD crew on their tech board the Blaster II includes the resistor ( 0.8 ohms ) to be ADDED to the original system even if it got the resistor in stock system. So MORE resistance is suposselly required to it. I have the screen shot of that but can't find it now
 

yella71

Well-Known Member
Local time
3:21 PM
Joined
Dec 18, 2018
Messages
1,822
Reaction score
2,733
Location
SW FL
check to see how much slop there is between the distributor and the drive in the engine. remove the cap and rotate it back and forth. could be quite a lot. my 383 had a lot and idled weird and had some jittery at low rpm. just a thought
 

66Satellite47

Well-Known Member
Local time
1:21 PM
Joined
Jan 15, 2015
Messages
6,902
Reaction score
5,957
Location
St Paul MN
What is the part number on your Orange box? I have several DC charts that show the ballast resistor values. Looks like .5 Ohm or .7 Ohm depending on coil.
 

Bee1971

Well-Known Member
Local time
2:21 PM
Joined
Jun 22, 2017
Messages
2,043
Reaction score
2,644
Location
Sobieski
Beat To Death

MSD Blaster 2 Instructions



Note: This Blaster Coil is supplied with a ballast resistor. If your application uses a points distributor, the ballast must be used. Late model electronic ignitions or an MSD Ignition do not require the ballast


STOCK POINTS IGNITION
If you are installing the Blaster Coil with the stock points ignition (Figure 1), MSD Blaster Ignition or an MSD 5 Ignition Control (Figure 2), the supplied 0.8 ohm ballast resistor must be installed on the coil positive (+) wire.


Now MSD interpretation of Late Model Electronic Ignition System

https://static.summitracing.com/global/images/instructions/msd-8203.pdf
 
Last edited:

66Satellite47

Well-Known Member
Local time
1:21 PM
Joined
Jan 15, 2015
Messages
6,902
Reaction score
5,957
Location
St Paul MN
One of my DC/Mopar Perf charts says use .25 Ohm resistor with Orange box & the Blaster coil( Blaster 1??) sold by Mopar Perf.
 

moparedtn

Ed on the Ridge
FBBO Gold Member
Local time
3:21 PM
Joined
May 14, 2011
Messages
15,396
Reaction score
26,819
Location
On the Ridge, TN
check to see how much slop there is between the distributor and the drive in the engine. remove the cap and rotate it back and forth. could be quite a lot. my 383 had a lot and idled weird and had some jittery at low rpm. just a thought
What was the "cure" - a new distributor/oil pump drive gear?
 

moparedtn

Ed on the Ridge
FBBO Gold Member
Local time
3:21 PM
Joined
May 14, 2011
Messages
15,396
Reaction score
26,819
Location
On the Ridge, TN
actually I read from MSD crew on their tech board the Blaster II includes the resistor ( 0.8 ohms ) to be ADDED to the original system even if it got the resistor in stock system. So MORE resistance is suposselly required to it. I have the screen shot of that but can't find it now
Naw, it says right on their website that no resistor is required for electronic ignition applications;
only those with points required a resistor according to MSD.
 

moparedtn

Ed on the Ridge
FBBO Gold Member
Local time
3:21 PM
Joined
May 14, 2011
Messages
15,396
Reaction score
26,819
Location
On the Ridge, TN
What is the part number on your Orange box? I have several DC charts that show the ballast resistor values. Looks like .5 Ohm or .7 Ohm depending on coil.
Heck I dunno, it just says "Made in USA" on the front as it came from Ma Mopar.
I guess I could uninstall it for a number on the back maybe?
IMG_20200622_081611553.jpg
 

moparedtn

Ed on the Ridge
FBBO Gold Member
Local time
3:21 PM
Joined
May 14, 2011
Messages
15,396
Reaction score
26,819
Location
On the Ridge, TN
Ok, so if the ballast isn't my particular issue, what do you reckon IS?
 

twecomm

FBBO Gold Member
FBBO Gold Member
Local time
2:21 PM
Joined
Apr 7, 2013
Messages
369
Reaction score
534
Location
Pittsburgh PA
The Mopar electronic ignition, orange, silver whatever color box you got, uses a single Silicon transistor ( the one on front heatsink) to mimick what the points did. That transistor is the device used to electronically "switch" the battery voltage to the coil thru the emitter/collector internal junction of that transistor. Silicon transistors have an inherent .6 volt drop thru that junction. So, when you are measuring with your digital meters, keep that .6 volt drop thru that transistor in mind.
 

Nacho-RT74

FBBO Gold Member
FBBO Gold Member
Local time
9:21 PM
Joined
Oct 8, 2012
Messages
5,713
Reaction score
2,220
Location
Valencia, España
You can or not be agreed with me, personally I'm not saying is correct or not, just what the tech crew at MSDIGNITION support board said. I couldn't believe it but captured the post screenshot for stuff like this. If I just could find it
 

Bee1971

Well-Known Member
Local time
2:21 PM
Joined
Jun 22, 2017
Messages
2,043
Reaction score
2,644
Location
Sobieski
"Reason I ask is I'm chasing down a slight "jittery" run condition under very light load, low RPM conditions (say, going down main street at 30mph at like 1700RPM) where the engine can be felt just ever so slightly doing a little jittery "dance".
(The same situation can be almost imperceptibly observed sitting still and revving the engine gently above 1500RPM or so, up over 2000RPM). There's tiny little half-assed jitters going on.
NOT actual misfires or anything like that and the condition can be quickly overcome with more throttle and/or load applied; further, when the car is accelerated, there's no issues and all functions like it should."




Whats your timing set at - Initial plus when does your springs , at what RPM does your distributor weight springs start to advance the mechanical curve to total ? You have your vacuum advance hooked up ? To ported or full vacuum if at all

Carb idle circuit - What Carb are you running ? How is the jetting specs and air idle mixture screws set at
 

68Moparmaniac

Well-Known Member
Local time
1:21 PM
Joined
Jan 18, 2019
Messages
1,356
Reaction score
2,618
Location
Utah
Some really good suggestions here, however I've run into that issue before and found that my timing chain was worn causing the timing to jump around a bit when it wasn't under load, went away when you squeezed down on the loud peddle. Sounds like a Saturday afternoon and a twelve pack kinda job... Good luck :thumbsup:
 

yella71

Well-Known Member
Local time
3:21 PM
Joined
Dec 18, 2018
Messages
1,822
Reaction score
2,733
Location
SW FL
What was the "cure" - a new distributor/oil pump drive gear?
Yes another pump drive that was good and I welded up the dist shaft end and refitted it to the pump drive. noticeable improvement in idle quality and running down the road at lower RPM.
 

yella71

Well-Known Member
Local time
3:21 PM
Joined
Dec 18, 2018
Messages
1,822
Reaction score
2,733
Location
SW FL
Some really good suggestions here, however I've run into that issue before and found that my timing chain was worn causing the timing to jump around a bit when it wasn't under load, went away when you squeezed down on the loud peddle. Sounds like a Saturday afternoon and a twelve pack kinda job... Good luck :thumbsup:
This....but my chain is new and the slop was the dist shaft and drive
 

66Satellite47

Well-Known Member
Local time
1:21 PM
Joined
Jan 15, 2015
Messages
6,902
Reaction score
5,957
Location
St Paul MN
I'd pull the distributor & look at the slot on top of the drive gear, I've had one that started to get a bit of a "bow tie" shape. But that was with big cams & valve springs, the distributor spade was fine. Timing chain sure could be it. Be sure the ECU case has a really good ground, the mounting screws may not be enough. Maybe a weak box or weak coil, but seems like that would show up at higher RPM's.

EDit: vacuum advance may be an issue, manifold vs ported? Initial plus vacuum too much?
 
Last edited:

moparedtn

Ed on the Ridge
FBBO Gold Member
Local time
3:21 PM
Joined
May 14, 2011
Messages
15,396
Reaction score
26,819
Location
On the Ridge, TN
Whats your timing set at - Initial plus when does your springs , at what RPM does your distributor weight springs start to advance the mechanical curve to total ? You have your vacuum advance hooked up ? To ported or full vacuum if at all

Carb idle circuit - What Carb are you running ? How is the jetting specs and air idle mixture screws set at
I set timing so it's around 35-36 "all in" (no vacuum advance), which with the distributor that's in the car right now puts initial at about 15BTDC.
(I don't know that I like setting a fairly stock 440 that high on initial timing, but that does work out to where the idle starts smoothing out well and I haven't heard any detonation, so...)
Advance seems to be occurring around 2200RPM or so.
(My TDC timing mark as indicated on the balancer is confirmed accurate via the piston stop method).
No vacuum advance hooked up - I haven't gone through that aggravation of adjusting that yet and the engine doesn't like it where it is now.
It will be connected to ported vacuum like it should be if and when I do go through that process.

Carb is an Edelbrock 1407 that came with the engine and is marked as "REMAN".
Yeah, I know, I know....but I've been though it and it is clean and useable.
Jetting on both sides was put back to what Edelbrock says those come with, exactly. Seems to work pretty well.
Very snappy as it should be.
Mixture screws set for best vacuum, then turned out about a half turn more fat from there.
Idle is 800RPM.

The engine itself is a stock rebuild '72 with forged internals, 452 heads and the famous Mopar 484 purpleshaft cam. Stock intake, Hedman POS headers, 3" duals (no crossover) inherited with the car.
Thanks!

(Edited to correct the type of carb and to confirm the model #)
 
Last edited:
Top