Greetings, gurus. Today is Help A Goon Day (that would be me). I see dual point distributors listed from time to time, why would someone want one? Is there an advantage over single point or an HEI version? I'm just curious...
Dual-point vs. Single-point distributors - pros and cons?
- Thread starter halfafish
- Start date
-
Longer dwell time it lets the coil charge up more.
Professor Fate
Push the button, Max...
Yep, longer dwell keeps the spark hot at higher rpms, single point units can fade as the rpms climb. Usually not an issue in day to day commuter cars, but is why you'll see them (factory) in rev-happy Commandos, 340s and other hipo engines of the day.
Cons are that good replacement parts are getting tough to find. (Big surprise there!)
Cons are that good replacement parts are getting tough to find. (Big surprise there!)
Mostly all 340's with a dual point distributor were 4 speeds. At least in '68 and '69.
67Dart273
Well-Known Member
There is more to it than just dwell. 340 dual points had a ball bearing breaker plate, and dual points last longer to some extent because each set only works half the time, so to say
Also, SOME dual points, like the old Prestolite hemi/ RB tach drive units, also had a ball bearing upper shaft bearing.
Also is point float is an issue in a single point, it is mitigated by a dual point, usually, given the same points are used.
Also, SOME dual points, like the old Prestolite hemi/ RB tach drive units, also had a ball bearing upper shaft bearing.
Also is point float is an issue in a single point, it is mitigated by a dual point, usually, given the same points are used.
j par
Well-hung Member
K.i.s.s. stop thinking of ways to make things more complicated!... With multiple cars and a truck in mid restoration there's way too many things to do to start making each individual thing more complicated... For instance on my last restoration there was many many more things I wanted to do but at some point with that vast amount of work to do I had to just keep things simple. Now once it's running and operating it's already given me more to do. And then when those things are ironed out then I can start getting complicated... My-2....
If you aren't racing and plan on revving the engine above 6,000 rpms... doubt you'll see big benefits from dual points.
The cast iron distributors also seem to last forever and don't wear the shafts and bushings as much.
Last edited:
Rat Bastid
Dunamis Metron
Any point ignition system will not have RPM retard like every other ignition system including the much loved HEI.
If you don’t know about and don’t measure the retard and then account for it, the points system will usually make more power than an electronic ignition system.
If you don’t know about and don’t measure the retard and then account for it, the points system will usually make more power than an electronic ignition system.
Not if you send Halifaxhops a PM.
Points are a mechanical switch. Mechanical parts wear, need periodic adjustment and maintenance ( cleaning, lubing etc..) replacement.
Electronic ignitions= no wearing parts, unaffected by RPM, dwell is solid and on some systems adjustable.
All modern cars for the last few decades are electronic. No fuss. As with any electrical system, keep connections clean and well grounded.
Electronic ignitions= no wearing parts, unaffected by RPM, dwell is solid and on some systems adjustable.
All modern cars for the last few decades are electronic. No fuss. As with any electrical system, keep connections clean and well grounded.
It was just a casual question for educational purposes. Don't get too excited about running my life for me.
To everyone else, thanks for the info.
The GM HEI ign is the way to go & simply hard to beat: cheap, reliable, minimal electrical connections [failure areas ], high spark energy [ 0.060" plug gaps].
The magnetic p/up type ign systems do retard slightly at higher rpms due to distortion of the AC output from the pick up [ explained in the link I posted in post #11].
The magnetic p/up type ign systems do retard slightly at higher rpms due to distortion of the AC output from the pick up [ explained in the link I posted in post #11].
j par
Well-hung Member
Stop trying to run his life... LOL.... He wants to know about dual points...
This was the last line of his question...
Hey man! I dumped my first points ignition in 1976 and never looked back. Even an old dinosaur like me knows that Points are up there with buggy whips and outhouses.
Professor Fate
Push the button, Max...
If it weren't for the parts availability/quality issues with points and especially condensors, I'd still use them in a lot of applications. Hell, the way things are going with electronic ignition component quality (or the lack thereof), I may still go back.
67Dart273
Well-Known Member
Capacitors (condensers) are no problem. You just don't use automotive capacitors. You use modern plastic AKA "orange drop" from electronics
I don't remember, offhand, what I use in outboards, .022 at 220V I think
I don't remember, offhand, what I use in outboards, .022 at 220V I think
Professor Fate
Push the button, Max...
Thanks- that would have been my next question!
67Dart273
Well-Known Member
Found this post, Halifax says they are .25--.28 mfd. You want at least 200V ratng or more
Going back to points
Decided I should go back to original points distributor. I've got nos points, a good used distributor, but I'm lost on the condenser. The original part number is 3420600, but will any condenser work, or is there a difference between them?
www.forbbodiesonly.com
Dave999
Well-Known Member
nice documnet on CIS/HEI as used on Jag/Triumph has section explaining why HEI is pretty good and why it does have some retard charactersistics as the rpm increases
obvioulsy this is just one mans view BUT if you check out the rest of his website link in the documnet, he does appear to be a cleaver chap. His spark energey measuring device is quite cool... and his CDI verse magentic coil igntion comparison is also good..... even if all you take away is an appreciation of the Bulls4it spouted in aftermarket igntion advertising its all a good read.
http://nebula.wsimg.com/5956cdbfbf7f...&alloworigin=1
ah link didn't work try this
HEI VERSUS STANDARD IGNITION & CUSTOMISING A RELUCTOR-HEI SYSTEM TO A TR4A
off target for the OP but HEI came up again..
Jags used a mopar LIKE pickup in a small cap distributor and a GM HEI module implemented with a nod towards the orginal Motorla application paper for the chip they made for the GM Delco Module
well i found it interesting
is there any advantage of HEI over single pont distributor?. Yes 50 years of technical advances....
chrysler removed the mechanical switch but did't increas current handling with a modern coil
GM changed the coil...... and that is where the benefit comes from.
HEI has faster switching time, becasue there is no arcing across the switch and no condencer suckig up some charge, at coil switch off.
HEI uses a coil of 0.5 ohm primary, and runs at 12 -14 volts and at higher current . It does its damndest to maintain 6 amps into the coil at mid to high rpm.
a points coil runs at 8 volts and the coil resistance and ballast resistor limit the current into the coil to 3 amps so that the points don't burn out.
the spark energy available with HEI dicates how wide you can go on plug gap, HEI specified a 45 thou gap for a big cap set up.
on a small cap set up run 35 thou for anything upt to 12:1 static 8:1 dynamic CR
more current = more intense magnetic feild in and around the coil. the coil is an laminate core e coil so the field leakage "around the coil" is lower and it runs cooler due to eddy current supression characteristics of the core design.
Faster switching means faster collapse of field which means more spark energy and higher voltage spark.
wider plug gap increases your ability to igntite a marginal mixture so a lean flat spot with points is no longer as flat with HEI. chaseing that progression flat spot by dicking with your carb is no longer necessary bcause its no longer there.....
your igntion spark energy is dicated by the coil and its primary resistance
the coils ability to create a high energy spark is dicated by the winding ratio and the current that flows in the primary
the effectiveness of sparking is dicated by how quickly you can get the magentic field to collapse and that is dicated by how abruptly you can switch off the coil
limits are therfore dicated by coil and the switch you use. provided all else like plug wires and cap are good.
the switch being points limits you to 3 amps or less and the current decreases as the rpm increases.
the switch being HEI limits current at low rpm to avoid coil over heating and burn out. and then does it best to mainatin 6 amps into the coil up to an rpm limit dictated by the module and how many cylinders you have. worst case with a modern module and a v8 is somewhere close to 6000 rpm and many do better higher for a 6 cylinder, and higher for a Special more expensive module when matched to a coil from the same manufacturer
HEI best bang for buck for a street driven -- quick squirt down the track at the weekend--- car.
lack of any other facilities, rev limit, start retard, etc means its not really a race set up.
but it kicks a certain amount of *** when compared with CDI. in fact there is little difference in spark energy, they both achive the same kind of output in different ways
when stand alone HEI E coil can be had for $25. a module can be had for £25 and a standard mopar electronic dizzy can trigger it.... you can't really go wrong... but its not for everyone
dave
obvioulsy this is just one mans view BUT if you check out the rest of his website link in the documnet, he does appear to be a cleaver chap. His spark energey measuring device is quite cool... and his CDI verse magentic coil igntion comparison is also good..... even if all you take away is an appreciation of the Bulls4it spouted in aftermarket igntion advertising its all a good read.
http://nebula.wsimg.com/5956cdbfbf7f...&alloworigin=1
ah link didn't work try this
HEI VERSUS STANDARD IGNITION & CUSTOMISING A RELUCTOR-HEI SYSTEM TO A TR4A
off target for the OP but HEI came up again..
Jags used a mopar LIKE pickup in a small cap distributor and a GM HEI module implemented with a nod towards the orginal Motorla application paper for the chip they made for the GM Delco Module
well i found it interesting
is there any advantage of HEI over single pont distributor?. Yes 50 years of technical advances....
chrysler removed the mechanical switch but did't increas current handling with a modern coil
GM changed the coil...... and that is where the benefit comes from.
HEI has faster switching time, becasue there is no arcing across the switch and no condencer suckig up some charge, at coil switch off.
HEI uses a coil of 0.5 ohm primary, and runs at 12 -14 volts and at higher current . It does its damndest to maintain 6 amps into the coil at mid to high rpm.
a points coil runs at 8 volts and the coil resistance and ballast resistor limit the current into the coil to 3 amps so that the points don't burn out.
the spark energy available with HEI dicates how wide you can go on plug gap, HEI specified a 45 thou gap for a big cap set up.
on a small cap set up run 35 thou for anything upt to 12:1 static 8:1 dynamic CR
more current = more intense magnetic feild in and around the coil. the coil is an laminate core e coil so the field leakage "around the coil" is lower and it runs cooler due to eddy current supression characteristics of the core design.
Faster switching means faster collapse of field which means more spark energy and higher voltage spark.
wider plug gap increases your ability to igntite a marginal mixture so a lean flat spot with points is no longer as flat with HEI. chaseing that progression flat spot by dicking with your carb is no longer necessary bcause its no longer there.....
your igntion spark energy is dicated by the coil and its primary resistance
the coils ability to create a high energy spark is dicated by the winding ratio and the current that flows in the primary
the effectiveness of sparking is dicated by how quickly you can get the magentic field to collapse and that is dicated by how abruptly you can switch off the coil
limits are therfore dicated by coil and the switch you use. provided all else like plug wires and cap are good.
the switch being points limits you to 3 amps or less and the current decreases as the rpm increases.
the switch being HEI limits current at low rpm to avoid coil over heating and burn out. and then does it best to mainatin 6 amps into the coil up to an rpm limit dictated by the module and how many cylinders you have. worst case with a modern module and a v8 is somewhere close to 6000 rpm and many do better higher for a 6 cylinder, and higher for a Special more expensive module when matched to a coil from the same manufacturer
HEI best bang for buck for a street driven -- quick squirt down the track at the weekend--- car.
lack of any other facilities, rev limit, start retard, etc means its not really a race set up.
but it kicks a certain amount of *** when compared with CDI. in fact there is little difference in spark energy, they both achive the same kind of output in different ways
when stand alone HEI E coil can be had for $25. a module can be had for £25 and a standard mopar electronic dizzy can trigger it.... you can't really go wrong... but its not for everyone
dave
Last edited:
Dave999
Well-Known Member
the link in what i posted didn't work so i changed it
-
