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HEI DUI vs MSD

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HEI DUI vs MSD

Postby 7racecar7 » Fri Apr 01, 2011 10:39 pm

For the interested;

Ive been reading these forums for about 2 years, and hopefully I now have something to contribute, or may over time.

Im running a 358 this year at dirt circle track, after years with a Crate 602 motor.

I have two distributors both HEI (limited by rules to HEI) MSD and DUI

Ive read pros and cons but I want to put it to the test so this season I will run both, off and on till one out preforms another (if i can notice).

So First Impressions.

1. Support - DUI seemed to have a nicer tone in helping me along the way, telling me they configured it to my engine specks, availability in general. MSD not so much but tone and telephone support is only a front door image, and probably who you get on the phone that day.
2. Taking it out the box. The DUI is much lighter and seems flimsy, Im worried. The MSD is a solid piece, both Bronze gear
3. Spark Plug Cables - Ive always run Scott and they have been flawless. On the MSD they fit perfectly, with the DUI they did not snap in properly and I had to call them back an order there live wires. not so happy about that.
4. Rev Limiter - MSD had one in stock, internal. DUI is an extra, and DUI is already more expensive then an MSD. So ill run my MSD external rev limiter (had on hand) on the DUI as I dont want to buy another one for 100.00 or so, only running rev limiter in case someone jacks me up and i dont get off the gas, dont want to crank it up and hurt the motor.
5 Advance Curve - DUI has it custom dialed in, the MSD is locked out. The Engine compression is a 12-1 and from what i understand having an advance curve helps in staring, although i spin the starter then hit the switch on the distributor after a few turns, and that helps as well from what I understand.

Ill keep you posted as to what I will find, some of you probably already know where im going to end up but im going to give this an up to date review, from ill call it an average racer view.

DUI posts a 55 plug gap comparable to a mag, Im going to start with 35 on both and bump them up, with the MSD prop wont go to much above 35. I run the non projected NKG heat 8, cross 133. DUI says to run a platinum version but I have not done the research on that yet.

Any advice or foresight is much appreciated.


Thank you.
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Re: HEI DUI vs MSD

Postby swatson454 » Fri Apr 01, 2011 11:26 pm

Subscribed. I've been quite curious myself.
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Re: HEI DUI vs MSD

Postby ProPower engines » Sat Apr 02, 2011 1:22 am

You need a kick ass ignition to fire at .050. I use a mag in our sprint stuff and they won't light above .035.
That said at 12-1comp. a .035 gap won't hurt and plug quality will depend on the engine.Some engines don't like some plugs and the AR133 is a plug that has a short life span in some applications.

The DUI stuff I have used has been top notch quality and in the 3 years in 1 car no issues. The rev limiter deal is just the way it is. External. At least if you have an issue std. HEi stuff will get you going again.
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Re: HEI DUI vs MSD

Postby ZIGGY » Sat Apr 02, 2011 7:57 am

I think Pro is right on. IMO the .050 gap is primarily a sales gimmick, although I think DUI's stuff & service are good. And like he says, you can always use stock HEI stuff in a pinch. And no, I don't think you'll notice any perf. difference between DUI & MSD.
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Re: HEI DUI vs MSD

Postby illfish » Sat Apr 02, 2011 8:21 am

I think if you read through your points one by one the decision will be easy. DUI: flimsy, wires don't fit well, etc. If you run the dizzy locked out, just throw a start retard on it to bring it back 15 degrees with ignition.
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Re: HEI DUI vs MSD

Postby billet » Sat Apr 02, 2011 9:21 am

I've opened the gap from .040 to .060 on the dyno with a DUI: [-X Lost 50+ HP on a 550HP 12.5 circle track engine.

The DUI also beat a 6al on the same engine by 38HP on the top end (7800). The MSD was the basically the same (actually +2hp) up to HP peak (6800) and then fell off.
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Re: HEI DUI vs MSD

Postby ProPower engines » Sat Apr 02, 2011 12:56 pm

Just as a point of intrest if you check some old tune-up books for earlier corvette's with a HEI ignition that the plug gap recomended was .060. There is not a stock HEI that will fire todays resistor plugs consitantly at .060 plug gap. Misprint? Who knows but I remember trying to get them to run at that and always had to go down to .040 otherwise it would miss like crazy under load.
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Re: HEI DUI vs MSD

Postby 7racecar7 » Wed Apr 06, 2011 6:17 am

Well 116.00 later and the live wires are here (17.00 shipping uhh) , they feel durable but are different from the scotts. the scotts have a sort of rubbery outside, the live wires have a mesh feel, like plastic but i dont think its plastic, and not using the word plastic to say cheap, the covers kink a bit when you bend them here and there but nothing that is unmanageable.

I run them under the headers and use some loom type clips and some chicken wire on one of them to keep them down as there is little bit of a clearance issue with the throttle link (little bit of contact but dont want to see me knock one loose one night)

with the live wires they did include an electric grease for the plug caps and a warranty sheet that you must use to keep the warranty, i guess to stop them from sticking on and someone yanking them so hard they come apart.

so all hooked up, i use a non projected spark plug: from various posts i hear the projected is more for nitrous applications, can have more issues then benefits and the non projected dissipates heat faster (assuming thats a good thing), also clearance issues but neither should have any issue with this applications.

I dont use anti seize, not sure if this is a good thing but the plugs usually come out weekly and so far I have not had an issue.

also the one comment: just throw a start retard on it to bring it back 15 degrees with ignition. That sounds like a plan
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Re: HEI DUI vs MSD

Postby ZIGGY » Wed Apr 06, 2011 8:00 am

7racecar7 wrote:i use a non projected spark plug: from various posts i hear the projected is more for nitrous applications, can have more issues then benefits and the non projected dissipates heat faster (assuming thats a good thing), also clearance issues but neither should have any issue with this applications.


Don't agree. IME extended tip plugs will often pick up hp. So long as you have the correct heat range, heat dissipation shouldn't be a problem.
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Re: HEI DUI vs MSD

Postby 7racecar7 » Wed Apr 06, 2011 10:32 am

ZIGGY wrote:
7racecar7 wrote:i use a non projected spark plug: from various posts i hear the projected is more for nitrous applications, can have more issues then benefits and the non projected dissipates heat faster (assuming thats a good thing), also clearance issues but neither should have any issue with this applications.


Don't agree. IME extended tip plugs will often pick up hp. So long as you have the correct heat range, heat dissipation shouldn't be a problem.


sounds like i have room for improvement then, ill put them on my list of things to try out. Thank you. If I dial in the non projected heat range is it safe to assume the same heat range would be correct with a projected head?
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Re: HEI DUI vs MSD

Postby ZIGGY » Wed Apr 06, 2011 12:35 pm

Yes, as I understand the ratings. However, any time I change plug no. or cross to another manufacturer, I'm cautious. Also, I don't claim to be a tuner.
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Re: HEI DUI vs MSD

Postby RCJ » Thu Apr 07, 2011 11:57 am

When I HAD MY imca spec motor onthe dyno it picked up 4hp with extended tip plugs (3911).Lost power when the gap was opened from .032 to .040.I use a msd hei with a 6 box hooked to it with the external coil.
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Re: HEI DUI vs MSD

Postby 7racecar7 » Thu Apr 07, 2011 9:12 pm

Well to make this all inclusive, mine as well talk about indexing now that a recent post reminded me, I do it but only for the reason of why not...Id think it couldn't hurt but here are the conversations:

viewtopic.php?f=1&t=19761&p=216037&hilit=indexing+plugs#p216037
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Re: HEI DUI vs MSD

Postby 7racecar7 » Thu Apr 07, 2011 9:27 pm

RCJ wrote:When I HAD MY imca spec motor onthe dyno it picked up 4hp with extended tip plugs (3911).Lost power when the gap was opened from .032 to .040.I use a msd hei with a 6 box hooked to it with the external coil.


Maybe I dont know enough but what makes a HEI a HEI? I though it was the fact that the Ignition Coil is within the distributor and eliminated the external coil. Although the way you describe the 6AL and External coil would you need to run a HEI?
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Re: HEI DUI vs MSD

Postby POS Dakota » Thu Apr 07, 2011 9:44 pm

7racecar7 wrote:
RCJ wrote:When I HAD MY imca spec motor onthe dyno it picked up 4hp with extended tip plugs (3911).Lost power when the gap was opened from .032 to .040.I use a msd hei with a 6 box hooked to it with the external coil.


Maybe I dont know enough but what makes a HEI a HEI? I though it was the fact that the Ignition Coil is within the distributor and eliminated the external coil. Although the way you describe the 6AL and External coil would you need to run a HEI?


HEI has the coil and control module within. This also eliminates the need for a coil wire.
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