DUI/ Hei installation... Plugs?wires?

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Dec 13, 2005
Vocano Island, aka big island hawaii
Just got my DUI from MAF, installing it this weekend.

OK well I am gonna run about 50=55 gap... if wrong tell me..

Now should I use a hotter or colder plug then stock? I mean would I still use that same plug I do now with stock dist?

Also what plug wires are you running .. Stock 6/Gm or a Make your self MSD/ Accel wires ?

Any other advice would be great
Stock plug gapped to .055 works great for me.

I have ordered all of the DUI's that I have installed from DUI, and ordered the wire set that they offer with it.

I do not see why you could not run a set of plug wires from a 1985-292-I6 chev engine...should work just fine.

Make sure that the distributor is seated when installed...that you do not install the vac advance against the side cover, possibly preventing you from getting it timed properly...you WILL NEED a longer bolt to use with the hold down clamp that is provided with the DUI...30mm comes to mind, but I am not 100% positive...I know it was significantly longer than a stock distributor clamp bolt.

Pretty easy swap. You will like it.

Good luck!

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I recommend using the stock GM spark plug gap spec for their distributor. There is no benefit from running a wider gap and it may be less reliable and cause problems with insulation breakdown and spark migration. If wide gaps were any benefit, all the manufacturers would use it.
DO NOT get the MAF plug wire kit... that thing is so friggin over priced, they want like $80 or $90 for those wires. I think I got mine from summit racing, just got a set of Moroso HEI do it yourself wires, much cheaper than MAF's wires and excellent quality. The wires have to be HEI specific or the conectors at the dist. end of the wire won't work with your new DUI. You'll definitely need to do a lot of timing work to get it all tuned in just right, mine was fine when idling and reving sitting in my back yard, but pinged like crazy under load. It takes a few tries to get it right, so be prepared for that. It's a great upgrade, I really am pleased with it.

Pinhead, I've read some of your comments concerning ignition stuff before and I think I don't understand where you're coming from. I've always been under the impression that a better spark provides a more complete combustion of fuel, thus resulting in more power. So that makes me think that the DUI dist. has to increase power over the worn out stock dist. I know for me I felt a seat of the pants increase when I installed it. Also, it seems like a bigger plug gap would allow for a better spark (when you have the power to make it bridge the gap)... It seems like if what you're saying about stock distributors and sparkplugs were true, racers wouldn't invest in stuff like MSD ignition systems. I know the NHRA all runs dual MSD Distributors and 2 plugs per cylander... I realize that this is an extreme example (7,000 hp engine) but if there was no benefit they wouldn't do it. Please help me clear up where I'm thinking wrong about this stuff... Thanks.
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Horsehead said:
I've always been under the impression that a better spark provides a more complete combustion of fuel, thus resulting in more power. So that makes me think that the DUI dist. has to increase power over the worn out stock dist.

It is not true. Its just marketing hype. As long as it sparks reliably, the fuel burns the same. Hotter spark, stronger spark and longer spark add nothing. Fuel combustion is complete with a stock ignition that is properly functioning because the amount of unburned fuel is about 1 part per million and it doesn't change when you change distributors.

OTOH, if your distributor is worn out and is not supplying a reliable spark on time, replacing it with any properly functioning distributor will be an improvement.

This is just my experience from 3 years of racing and dynamometer tuning. Getting the advance curve dialed in makes a noticible improvement, but increasing the voltage is not necessary on a normally aspirated gasoline engine and by itself, I never saw any benefit. It also has a distinct down side in the fact that excessive vlotage leads to reliablility problems and failure. Racers (and ex racers like myself) use electronic ignitions because they provide a reliable spark at high RPM (>7,500 RPM) where stock coils have problems with incomplete saturation. Supercharged and nitromethane engines require a hotter spark to ignite reliably.

The reality check is that if there was any significant benefit, all the automobile manufacturers would be required to have them, because incomplete combustion is a significant smog issue.
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Doesn't a larger gap also place more load on the coil? I run an HEI and gapped the plugs at .035 and have had no problems. I also used the "make-it-yourself" plug wire kit, much <$.

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Well my stock distributor was very problematic. We'd rebuilt it once and done put on at least 2 caps and 2 rotors to no avail. It was time for a new dist. and i just decided "hey, why not go for broke" and got the DUI system. That's probably why i felt so much seat of the pants power... that and the tuning it in just right. I humbly bow before you pinhead. Seriously tho, your knowledge of all this stuff usually amazes me and I'm thankful for your patience with a kid like me who don't know nuthin more than what he's heard from the people trying to market their own products... haha. I stand gladly corrected.
What is involved in properly tuning the DUI besides timing? I just set mine at the normal timing mark and it seems fine. Would performance improve if I timed it differently or is there some other adjustment? I set my plugs at 55 and use the livewires. New dizzy and wires came with a truck I paic $800 for so I decided to try it. Seems to be quicker.
Hello, i too purchased the HEI/DUI from Performance Distribitors( they are the specific builders that MAF gets them from). A tech from there company advised me to run Autolite platinum plugs@.055 cap, with 12 degrees timing. He said they recommend their Live Wires. He told me if i didn't want to spend that much money,then i should search for a wire that was 8mm, spiral core,with a ohms resistance of 300-350 per foot. No more no less. I called performance places(locally and internet),hot rod shops, read research on the net, talked to people,etc,etc,etc. Some said it was important for breakdown, etc. Some didn't think it was.Totally confusing.Most companies only had wires around 900 ohms per foot. And the prices weren't that much cheaper.Perf Distribitors had the set pre cut and booted with weather tight boots shrunk, specific to my 2F. So i just did it. Simple and i will say that it was a noticable improvement over stock set up.I mean a NOTCEABLE improvement. Good choice on the HEI/DUI you'll like it.
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lavarunner said:
no one is mentioning any thing about a hotter or cooler plug.. why?

It is a different issue. Just run the stock heat range unless you are having trouble with the plugs fouling nd then bump it up a heat notch.

When I first started street racing I used to blow all my paycheck on my car. Every time I dropped $200 or more on an engine upgrade or doodad like high energy, high voltage ignitions, I would start it up and think "Wow, I can really feel the difference with all that power now". Then I would take it out to the track and many times find out it was no better than before I spent my money. What I learned from all this is that feelings are no substitute for quantitative measurements and that the things that significantly increase power all involve getting more air/fuel mix in the cylinders.
Burning more fuel with a turbo will generate more heat, so you may need a colder plug. It will also depend on the load and speed you operate at. A higher density fuel charge also requires a higher voltage to make a spark across the plug gap, so keep the gap within normal specs. Longer gaps also require a higher voltage to jump the gap, so you could get into trouble with insulation breakdown. High voltage will always find the easiest way to ground.
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The DUI setup has a couple of advantages not really related to performance. It's new, or at least professionally rebuilt, it's curve is setup to get smooth accaleration from the particular engine it's bought for, it's easy to hook up and does away with aged pieces and wiring in the ignition system in one quick stroke, it uses vacuum advance to further tailor the spark to load conditions (requiring on many of the cruiser engines that a modified, aftermarket or offshore Toyota carb be used), and it's got a tach connection if anyone feels the need for that capability. Also you can get a coil, ignition module, cap, rotor, or pickup coil at most any auto parts place on the continent.
There aren't many vacuum advance only distributors from Toyota and the old models that do are no better than archaic old Delco jobs from 1950 GM trucks. The newer ones also require a side cover change and aren't much cheaper in similar condition than the DUI is, if at all cheaper. Used ones are out there but you take your chances with those so it's good to rebuild or have them rebuilt which then jacks the price right up over the DUI and you still have that stupidly mounted coil on the fender (2F).

In light of all that I think DUI is a pretty good choice if you have distributor problems.

(and a cold engine starts fast with that big hot spark)
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lavarunner said:
no one is mentioning any thing about a hotter or cooler plug.. why?

I'm running a cooler plug from NGK gapped out to 0.55 with the DUI. I bought wires locally through a racing shop 8mm or 9mm ( I can't rememeber). I ended up paying around $40 for generic big block motor wires. Those are the kind you cut and crimp yourself.

I also raised the combustion on the motor through different pistons. Ross Racing Pistons made mine based off of molds from my combustion chamber. I'm running about 9:1 now. Raising the combustion ratio was my reasoning for running cooler plugs.

BTW, this is on an '84 2F.


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I have had HEI on my 2F for 6 years now I use stock Toyota plugs .55 gap and DUI Live Wires works great. the only thing I added was I silcone the cap shut and added a breather tube.
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