Which Duraspark?

I asked this before but can't find the post now.

Anyway, I am going to purchase a DurasparkII distributor for my '66, I see that single vacuum advance and dual vacuum advance units are available. Which one should I get? What is the difference?

Get the single vacuum/mechanical advance

Slade

Hey I66
I know, I actually posted a reply to u on this but the next day is when all that mysterious posts/topics and user passwords were lost etc, well mine and a few other ppls were.

Anyhoo, I tried doing a search on it but I wasnt coming up w\ anything useful, it was confuzzlin. I dont know anything about these kinds of distributors since the only ones I have tinkered w\ were computer control, no vacuums and I jus move the distributor itself, nothin else to mess w\.

ANyways, it jus loox to me like dual simply means jus that it has 2 vacuum advances, how this is advantageous, I don know, unless, it allows for more advancement throughout the RPM range, like, the one vacuum allows 20deg of advancement total and so it reaches that point at X rpms, whereas having another vacuum may then allow more advancement throughout the rest of the rpm range ?? I really dont know, I'm jus kinda guessin, sorry.

Thanks guys, I'll get the single vacuum unit. That and an MSD box and coil should spark things up pretty good.

The dual vacuum canister allows the system to use vacuum to retard the spark by adding vacuum to the other side of the diaphragm. It's another emission device. You can use a dual vacuum distributor, just plug the unused port closest to the distributor.

What's the theory of the electronic parts? I put in the Pertronix. I understand points and gap and voltage saturation from the coil.
So what's the magnetic tape around the rotor and what do the different parts of the Duraspark do, the box and the magnetic tape and the modular thing under the cap. Why can you use any box, GM or MSD if it's compatible with the DSII, etc. HMMM?

I don't fully understand these electronic ignition systems but I won't let that stop me.

The electronic distributor sends a low voltage, low amperage signal to the spark control box which, in turn, grounds the coil through a heavy-duty transister that can handle the amperage.

The points distributor grounds the coil through the points.

The elctronic distributor uses a different kind of coil to get the most from the more precise timing and dwell achieveable with the electronics. It has a faster rise and fall time of the field and so gives a more precise spark. The transister can also handle more amperage than points can and therefore, you can get more power through to the sparkplug.

At least, I think so........

you put the thingy in and the other thingy goes round and round but electronically instead of mechanically making the wires go"buzz buzz" and the spark thingys go "spark, spark"...

ahh sleep deprivation....

Adding to what Rande mentioned the elctronic module and magnet ring is nothing more than a switching device. Pertronix does not make a conversion kit for my Vette's old dual point distributor. I put an MSD box on its ignition, and now my points just act as a switching device for the MSD box. With the old setup, my ignition quality used to deteriorate in a few thousand miles. Now the points do not see the amperage as before and I have not had to change them. Some electronic ignitions used optical sensors to trigger the external ignition circuitry. The Pertronix unit is a Hall effect sensor or switch. As mentioned, the advantage of electronic ignition is more accurate timing. I also think the increased output of a inductive system is due to the faster response time and increased dwell of the "switch" Which allows the coil to saturate and discharge more fully delivering more energy to the plugs.
The link below explains Hall effect sensors.
http://www.wellsmfgcorp.com/counterpoin ... int3_1.pdf

Veeery interesting. Now a follow-up question. Mallory has a points dizz with mechanical advance. Do I keep the points and use the box or is there another mod, like the Pertronix where you pull the whole deal and just leave the rotor?
Also, how about the web address for Mallory. Does anyone have it? I took about four web searches before I got it and then stepped away from the computer. Just like the work bench in a family house, I laid down my tools when I was called away. Nothing was where I left it when I went back. Help!

The Mallory website is: www.mrgasket.com/mallorymain.html

I'm not too big of a Mallory fan, their dual point dizzys and older stuff is cool... But that (P)Unilite dizzy sucks... Isn't it funny that Pertronix makes a unit to replace the unilite module for unilite distributors?

Ludwig, I am not familiar with the Duraspark set up, and its external box etc. The Pertronix unit has tape that retains 6 magnets in on the rotor shaft. Mechanical distributor could likely be converted to a solid state ignition with a Mallory Uni-lite kit or the Pertronix. The MSD box just needs a signal either from a set of points, a solid state ignition setup or a crank position sensor. It doesn't care if it is from points or an electronic device. I have one car triggering an MSD off of points, and another running it off of a Pertronix
Mallory is a Mr. Gasket company
http://www.mrgasket.com/

Thanks for the heads up, both you guys. When I first put the Pertronix in, the idle spiked like from 700 to 1500 and I had to turn the idle way back. It's great and I've had good luck up to now, but I have some misgivings about the unit after reading FSP how it pooped out here or there. Maybe I'll but an extra Ignitor II in the glove box and take the points out of there too.
I'm getting a little mis-fire at idle so I've been considering a little beefier setup. This info on Mallory is all good.

I have not had any failures on the Pertronix, and have had them for several years. When I did install them, I always had to readjust my timing. In all cases, my idle speed picked up. It appears that the setup itself may tend to advance the timing when installed.

In "How to build Horsepower" by David Vizard, he writes that there was a misfire rate of up to 15% on mechanical (points) ignition and that falls to something like 1% or less with electronic. I had to be getting a misfire rate of close to that before. I'm sure that more successful ignitions per revolution is part of the reason for the increase in idle, although I'm no engineer. Maybe it is just the unit and a built in advance, like you say.

I agree with your comments about the misfire. My old Vette used to foul plugs and had a lot of misfires at idle due to the dual 4bbl setup. It does not have the Pertronix, but does have the MSD box. When I installed the MSD box, the idle smoothed out, which I attributed to better ignition firing. It also does not foul out the plugs now.