DUI upgrade on 4.2...hints? - JeepForum.com
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post #1 of 15 Old 08-15-2017, 05:56 AM Thread Starter
davjohns
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DUI upgrade on 4.2...hints?

I've been sitting on a new DUI dizzy, MSD wires, and NGK Platinums for about three months. The physical swap is no problem. My concern is the electronics. I know it is supposed to be simpler, but I'm hesitant about what do on the resistor.

Currently, the red 8 gauge wire from the wire harness attaches to a white device on the firewall that has clearly been added by someone. My guess is that this is a resistor. But it runs to an old school dizzy, which I find odd. It appears the Nutter bypass was done on this girl. Is a resistor a standard part of the bypass?

I think I should eliminate that resistor when I swap to the DUI. I am thinking the 50K volt coil will want less resistance feeding it. Correct?

It would also be nice to know exactly which wire to connect to the dizzy for the tach. I think there is another wire that goes to the control module, correct? Anyone know which color that is? I could probably just trace it back through the loom and pull it. There are too many wires under there now that all of the pollution control stuff is gone. I probably need to clean up the loom anyhow.

So...two questions: 1) Should I eliminate the resistor? 2) What color is the wire to the tach?

If I need to leave the resistor, please explain why. I'm rotten with electronics and have convinced myself that I have the right answer on this one. lol

David

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post #2 of 15 Old 08-15-2017, 06:27 AM
dsaylor
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The resistor is unnecessary. The HEI distributor is a two wire hookup. One wire if you donít care about a tach. Some say you need to run a relay for the full power of the HEI, some say you donít. Iíve run both and currently have a relay. Iím not completely sure if itís really improving the performance, but I get the logic behind it. I donít know what year your Jeep is, and it could be different, but on mine the green wire going to your existing coil is what you need to power your tach.


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post #3 of 15 Old 08-15-2017, 06:57 AM
Beach248
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This might help:

http://www.jeepforum.com/forum/f8/co...r-hei-1317248/
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post #4 of 15 Old 08-15-2017, 07:11 AM
Chrisnvegas
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Platinum and iridium plugs are a performance downgrade from the original copper.
Copper is a better conductor.
Copper won't easily overheat like the exotic metal plugs.

Overcome advertising.
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post #5 of 15 Old 08-15-2017, 10:44 AM Thread Starter
davjohns
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Now that you mention it, I'm not positive they are platinum. Sounds like the kind of snazzy name I would ordinarily steer clear of. I'll double check and change them out for copper if I made that mistake. Thanks!

David
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post #6 of 15 Old 08-16-2017, 10:49 AM Thread Starter
davjohns
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I wrote Performance Distributors to be on the safe side. They confirm that the coil will want full power. They said nothing less than a 12ga wire to feed it. If I recall correctly, the red wire is an 8ga and should be ok.

David
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post #7 of 15 Old 08-17-2017, 02:00 PM
mike134
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I wouldn't say its all advertising on platinum and irridum plugs. They do in fact last longer. Try using copper in a grand prix or buick century where you have to physically rotate the engine on its side to change the spark plugs due to horrendous design. You're really going to want those platinums in that application so you only have to do that one time.

Your jeep is so easy to change the plugs though, and the copper give you much better performance!

The resistor you are talking about is used because the old ignition coil couldn't handle a direct 12 volt supply indefinitely. They used to feed it 12 volts on start up and about 8.4 volts on RUN. Totally unnecessary with modern technology.

Another thing to note, your spark plugs should be gapped wider with the new coil. You can use the stock plug gap, but you basically lose the benefit of the hotter coil. The new spark should have about 30% more surface area for igniting the cylinder.
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post #8 of 15 Old 08-23-2017, 10:04 AM Thread Starter
davjohns
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Turns out I went with Champion copper plugs and just remembered wrong.

The swap of the distributor was straight forward. The DUI is much larger in diameter and has far less clearance from the block. That's a little awkward, but once it is in, there's no issue. I got wires for a 4.0 because someone said they are a bit longer. If they were any shorter, they wouldn't have worked at all. As it is, I wish they were a bit longer. They'll do.

I have the red wire for the 'batt' hookup and the green wire for 'tach'. Both are a bit short to reach comfortably, so I am going to extend them and put them in a loom. Over the years, she has had emissions junk and other things removed, which has left wires everywhere. I'm going to trace the wires from the old dizzy back to the ECM and just remove it all. There is also some kind of cannister below the ECM that I suspect was a charcoal filter for the emissions. It will go as well. I just ordered split loom and clips to clean it all up. There are connections for diagnostic equipment beside the hood hinge that have to go as well. Even if someone had the diagnostic equipment to hook up, I can't imagine it works.

I'll post again when she is running and report on any improvement in performance.

Appreciate the input.

David
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post #9 of 15 Old 08-23-2017, 12:45 PM
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Quote:
Originally Posted by davjohns View Post
Turns out I went with Champion copper plugs and just remembered wrong.

The swap of the distributor was straight forward. The DUI is much larger in diameter and has far less clearance from the block. That's a little awkward, but once it is in, there's no issue. I got wires for a 4.0 because someone said they are a bit longer. If they were any shorter, they wouldn't have worked at all. As it is, I wish they were a bit longer. They'll do.

I have the red wire for the 'batt' hookup and the green wire for 'tach'. Both are a bit short to reach comfortably, so I am going to extend them and put them in a loom. Over the years, she has had emissions junk and other things removed, which has left wires everywhere. I'm going to trace the wires from the old dizzy back to the ECM and just remove it all. There is also some kind of cannister below the ECM that I suspect was a charcoal filter for the emissions. It will go as well. I just ordered split loom and clips to clean it all up. There are connections for diagnostic equipment beside the hood hinge that have to go as well. Even if someone had the diagnostic equipment to hook up, I can't imagine it works.

I'll post again when she is running and report on any improvement in performance.

Appreciate the input.

David

Yes, that's an emissions charcoal canister. However if you don't have emissions testing and remove it, you'll likley experience gas odor in the cab. It's not hurting anything being there and doesn't have any negative impact on performance.

As for plug wires, you should be running 8mm wires with an HEI. '80 Ford Fairmount wires for an I6 motor work really well and are 8mm in stock form.
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post #10 of 15 Old 08-28-2017, 08:26 AM Thread Starter
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As for plug wires, you should be running 8mm wires with an HEI. '80 Ford Fairmount wires for an I6 motor work really well and are 8mm in stock form.
I got MSD wires for a 4.0 because someone said the wires for the 258 would be too short. The DUI is taller than stock and the reach for the wires is greater. I found the #1 and #6 wires are still too short to adjust the timing properly. So, I've ordered the MSD universal kit so I can make custom length.

I tried going to the auto parts store for wires. The kid at the counter was confused by anything but what he could look up in the computer. I couldn't remember the models of car people had recommended as having longer wires, so I told him to check a 1970 Nova with a 250. He asked me what size engine. I said 250. He told me it didn't come with a 250. I turned the screen around and explained to him that the 4.1L that was followed by '250' indicated it was 4.1L in the metric system, but in 1970, American engines were only described in terms of Cubic Inches and this one was 250CI of displacement. He was pretty surly after that.

New wires will be here tomorrow. She runs, but I can't adjust the timing to optimal without the longer wires. I also think I am going to have to run a new wire to power the dizzy. The red wire that ran to the old dizzy was thinner than I originally thought. I think it is starving the coil. I'm thinking of running it straight from the relay mounted to the fire wall.

David
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post #11 of 15 Old 08-28-2017, 09:19 PM
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That's just one more reason I hate people.

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post #12 of 15 Old 08-28-2017, 11:26 PM
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That's just one more reason I hate people.
That's cause you only deal with Low Lifes, us High Lifes are much better.
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post #13 of 15 Old 08-29-2017, 01:44 AM
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That's cause you only deal with Low Lifes, us High Lifes are much better.
When I say "people" I don't mean average everyday run of the mill go to work for a living, don't beat your wife and children type of people.
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post #14 of 15 Old 08-30-2017, 08:44 AM Thread Starter
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I ordered a set of MSD universal wires. Now, I can make them the length I need so I can organize them pretty under the hood. So, I have a set of MSD Super Conductors for a 4.0 that need a home.

David
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post #15 of 15 Old 09-13-2017, 06:35 AM Thread Starter
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This was a bit more difficult than anticipated, but it is working out.

The MSD wires were not long enough for me to adjust timing on the new dizzy. I ordered the universal (cut them yourself) set. Those took a while to assemble. When I put it all together, she wouldn't start. I think I had messed with the timing after getting her started the first time. So, I questioned my handiwork at the new wires and returned to the old ones. Still wouldn't start. Then, I remembered that I turned the dizzy back after getting the girl to crank before, so I turned it back the other way and got her started and running better. Now, I have to return to the universal wires to clean it all up. Plus, I still have some rough idle and I think I might reduce the spark plug gap to .045. I set them at .050 due to Performance Distributor's recommendation, but so many people make good arguments for .045 being the max. Plus, I want to run a clean 12v wire to make sure that isn't a limiting factor. Again, people argue it is not necessary, but I want to eliminate all issues by running a clean power source before reducing the gaps and checking the universal wires.

I drove her this morning. She didn't seem cold natured like she has been. I also think she might have been taching up more, but I haven't re-connected the tach wire yet, so I couldn't be sure. She has always started right up, but she sometimes started and died previously. She seems to just start and keep going now. I'll know the true results better once I finish.

I also have lots of excess wiring in the loom that has to go. LOTS!

David
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