HEI DUI vs MSD

[SLPRACINGENGINES]

dui all the way..i have ran them for years in classes that spec..that you must run a hei type dist..as far as the 55 plug gap..never used it that high..i always run .40..i have a davis dui that i have had for 12 years and its still running strong..he makes a top notch piece of equipment.. GOOD LUCK MAN!!!!!!!!!!!

[Horndog]

DUI user here too. Quality components.

[7racecar7]

Well,

I have to report it as I started this comparison, this weekend the coil on the DUI went at the tail end of a heat race, power just fell on its face then a couple of lout bangs and that was that. Coil got fried.

So Issues with both MSD and DUI in the long run. The DUI i sent back to DUI early this year for them to go over. Came back and this was the second race of the season that I used it.

Now I understand electronics fail and I dont think there is a test you could have done to foresee a coil failure.

So it total review over the past 2 years I have to say that my MSD felt more crisp and responsive than my DUI ever did. I never had any issue with the MSD losing its timing or retarding as timing went up. With the DUI the timing when out with running the advance and even when I locked it out it still retarted with little slop in the gear.

I went with DUI from all their reviews in circle track and I see their ads everywhere and bought into their website information. It turns out the same guy writes the same articles that promote the DUI. The questions they ask up front i though there were many more things to tweak in setting a HEI but in the end I have to ask what really can be done? From what Ive learned there is really the housing, the shaft, the gear, shim stack, pole or coil pickup, module, roter, coil, and rotor cap it seem straight forward now and well maybe you want to run an advance curve so that it starts better but really you can spin the starter then flick the switch to the HEI and there you go.

The MSD feels like a more durable product (pro billet version) but really that is only the housing. The MSD could also use Scott wires and the DUI you had to buy their live wires as the Scotts would not fit their cap plugs.

For me Im sticking with the MSD and maybe ill test out the Mallory against the MSD for the next two years. That sums up the best I can give back for now to this forum that has helped me in may ways.

Thank you.

[barnym17]

You might try the accel 300 ignition with the 375 controller.I have been using one for a while now and really like it.One neat feature if dirt tracking is the timing retard feature simply wire in a toggle switch and flip it on for legal traction control.You can set it to pull up to 15 degrees of timing when activated adjustable by .1 degrees so you can dial in what you need to help keep hooked up on a slick track.

[RevTheory]

I almost hate to bring this up but I can't find the other old-as-dirt one I was looking for

This thread did show that an inductive discharge, single-coil ignition can run upstairs in a WOT application very well compared to a CDI but how about down low at throttle-restricted cruise?

MSD says something along the lines of "multiple sparks at low rpm for better torque.." or something along those lines but I've heard others say that it's marketing bs. I've heard that the short pops won't reliably get the kernel going so they have to hit it several times in hopes that something "sticks".

I've heard that inductive discharges fire plenty hot enough and are a much-longer duration than CDI charges and do a better job in my scenario. My application doesn't have room for an HEI but I'll still get the choice of hooking up a box or going with the inductive discharge. I just want to know what's what and what's marketing bs.

Are there any performance tuners with all the electronics to monitor the exhaust who've seen misfires with either style that didn't happen with the other style?

[amc fan]

Do you have to run coil in the cap? Can you run external coil ?

[RevTheory]

Do you have to run coil in the cap? Can you run external coil ?

No room so definitely a remote coil and a small-cap distributor.

[amc fan]

I think you need to read Dr.Christopher Jacobs PH.D., E.E. book on Ignitions! Inductive puts out longer duration of lower current and capacitive shorter duration but higher current. He also talks about using an extra small battery(motocycle)to boost voltage to 24 volts when floored and has diagrams an explation of his thoughts. He cautions not to keep on full throttle more than 20 seconds with 24 volts... so as when you let off the throttle they will cool down. I would think more than 20 seconds parts will burn/blow out!

[wyrmrider]

better pull your leggins up when reading Jacobs

[barnym17]

If you want an hei and don't have room solution is use any mag triggered dist, remote mount the module and coil.Both systems have advantages and disadvantages I would guess based on oem experience the hei would be better for part throttle cruise firing lean mixtures as that is why it was designed.Trust me if the cd type ignition would have been better for this all the oems would have used them in the 70's and 80's when they were fighting emissions and fuel economy battles with carbs.

[racear2865]

better pull your leggins up when reading Jacobs

As per wymrider, you better pull your leggins up to your neck when u read Jacobs
reed

[RevTheory]

There are a couple of small-base distributors I'm looking at. Kind of eyeballing one with a dial-in, electronic curve but that's another topic. I really just need to decide on what type of spark to go with (CDI or inductive) and whether or not there's anything more than hype to the multiple spark deal.

[Ks Fats]

X 3 on the wymrider post; from what I understand the "multiple spark" feature drops out after a specific r.p.m. and reverts back to single spark mode. The inductive vs. capacitive issue is ongoing but I think research will show inductive to be most common. Its been many years ago but I seem to remember an o.e capacitive system made by Prestolite that was a disaster in terms of reliability; maybe someone with better long term memory can verify.

[JCR]

Here is a good post on the history and why the HEI was so good. http://www.slantsix.org/forum/viewtopic ... 749#161749
A post on retrofitting HEI to older engines. http://www.slantsix.org/forum/viewtopic.php?t=15779

CD ignitions were offered by the some OEMs starting in the late 60's. The Magneti Marelli Dinoplex and later by Bosch as used on 911 Porsche during the 70s. These CD ignitions fell out of favor as inductive ignitions had more sophisticated electronics applied. From the primitive transistor boxes to later ECMs. I cannot think of an automobile sold today that uses a CD ignition. The OEMs want a long spark duration that inductive ignitions provide. The CD ignitions can't do this even with multiple spark.

[amc fan]

Hey I replaced my Judson Electronic Magneto with a Procomp Coil and my car starts and runs better!