I installed the Davis Unified Ignition (DUI) HEI last weekend. The DUI HEI is made by Performance Distributors
This post isn't so much as "how to" writeup as it is just a documentation of my experience. I ran into some problems during the install process due to my own inexperience. Unfortuately all of these photos only show the steps leading up to the actual install. I will give as much detail as I can about the trouble I ran into, however.
The DUI HEI replaces several parts of the stock ignition system:
- Ignition coil and horseshoe connector
- The ignition module (silver box under the coolant bottle)
The DUI is also designed to connect to the manifold vaccum for advance, instead of the ported vacuum as is commonly used.
Here we see the wires to the stock horseshoe connector:
Here we see the wires and connector leading to the stock distributor. You can see the wires were spliced as part of the Nutter Bypass:
Here's my Team Rushed distributor cap:
The wiring has been disconnected from the coil:
Here's the stock hold down clamp for the distributor. It has to be removed to get the dist out:
The DUI directions tell you to mark the position of the rotor before you remove the old dist. Here I have put two white soapstone marks on the valve cover:
Here's the old dist:
Here's the hole where the dist goes. You can see the gear inside:
The remains of the old gasket between the dist and the engine block.. the DUI comes with a new gasket.
Here's the new unit:
Here's the inside (distributor cap removed):
The DUI comes with a new hold down clamp, gasket, and 2 electrical connectors (one for power to the unit, and another for connection to a tachometer)
I lined up these parts for the install: New Autolite 985 spark plugs, 12 gauge copper wire, heat shrink tube, and a connector reccomended by Jeephammer in this post
The connector fits into the 2 prong connector that goes to the stock ignition module (silver box). From this new connector, you run a 12 gauge wire to the DUI. This accomplishes a couple of things (see Jeephammer's post), and serves as an easy way to get power to your DUI. Note that the DUI install directions aren't Jeep specific, so there is no guideance about how to deal with Jeep-specific issues.
The 12v+ and tach connectors included with the DUI are OK, but it's not clear how to correctly assemble them. Here we see the correct positioning of plastic and metal parts. It took me probably 30 minutes of soldering and cursing and re-working to get these dang things right.
So, that's it for the photos.
During the install, I followed the DUI install directions as exactly as possible. I spent probably 30 minutes installing and reinstalling the new distributor and was never able to get it to line up correctly. It never seemed like it was lining up right. I finally got it in, but when I went to fire up the engine it would not start. It made some strange noises but never fired up normally. Clearly there was a problem.
I posted to JF to get help
, and it was obvious that I was going to have to find TDC (top dead center) of the compression stroke on cylinder #1. That was the only way to make sure the distributor was in sync (timed correctly) with the other parts of the engine. This was the first thing to do.
Finding TDC isn't as difficult as it may sound. I used the chopstick method:
1) Remove all spark plugs.
2) Remove distributor.
3) I already had the battery disconnected.
4) Find a wrench that fits on the crankshaft pulley. I used a 10" Crescent wrench, because there was not enough room to get a socket in there.
5) Use the wrench to turn the engine clockwise a little bit at a time.
6) put your finger over the spark plug hole for cylinder #1. This is the one closest to the radiator.
7) When you feel pressure in the #1 cylinder that pushes your finger off of the hole, then you've found the compression stroke.
8) Put a chopstick (I used a bamboo BBQ skewer) into spark plug hole, but don't get it go. You should feel it hit the piston.
9) Continue to rotate the engine and the chopstick should push upward. BE careful because the chopstick will tend to bind up since it's in there at an angle. You may need to pull it out slightly while you're rotating the engine.
10) When the stick ceases to move upward, then you've found TDC. YOu might have to turn the engine the other way to lower the stick downward and then bring it upward again to be sure about the TDC position.
11) Once you have TDC, look at the timing marks and see if the hash mark (white line) is near the 0 on the timing scale.
Once you have TDC, then the DUI can be installed. You need to know one really important concept
at this point:
The rotor must be pointing to the terminal (in the distributor cap) for spark plug #1 (or just before the terminal).
It is my understanding that it is traditional to have the #1 terminal toward the bottom of the distributor, so I postioned the rotor pointing down (away from the engine) and stuck the DUI into the engine block. When you stick the dist in the engine, te rotor will turn a few degrees because of the helical gears meshing.
Again, the trick is to know exactly where the rotor is pointing, and stick the cap on so that terminal #1 is on the roto
r. This ensures that spark plug #1 will fire on the compression stroke of cylinder #1 which ensures that everything is in sync.
The big mistake I made during the failed (first) install was this:
When the distributor is installed and the cap is on, you can turn the distributor, but the ROTOR DOES NOT TURN
. It stays stationary. So if you turn the distributor to some other place, then terminal #1 isn't lined up
correctly and nothing's going to work right becuase it's all out of sync.
I suspect that my original install attempt would have worked if I had understood this concept.
If you read other posts of how-to's about installing distributors, people will often say that you need to make a mark on the distributor body. The main goal to accomplish, assuming you've found TDC for #1 (on the compression stroke), is that the rotor needs to be in line with terminal #1 on the distributor cap. How you get it to line up is up to you. (eyeball it, mark the body, whatever)
There is one other confusing thing here:
The distributor shaft also serves as a means to drive the oil pump. The tip of the dist shaft looks like a flat head screwdriver, and fits into an accompanying slot inside the engine. The position of that slot in the engine does NOT relate at all to the timing or the position of the distributor
. The problem is that you may be unable to get the distributor seated all the way because that slot isn't lining up. BUT, this is easily fixed because you can turn the slot without having to worry about goofing up the timing. You can use one of two methods:
1) Stick a screwdriver into the distrubutor hole in the engine, and turn the slot to the position you need.
2) Instal the distributor as far as it will go, then use your wrench to turn the engine 2 full rotations. This will bring you back to TDC, but it will allow the oil pump slot to fall into place with the dist shaft. This is the Jeephammer method. If you note the hash mark's position to the timing scale numbers, you can be sure you've done 2 complete rotations and be sure you're back at TDC.
So, to sumamrize again, find TDC, figure out whre you want your rotor to be, look in the engine to see where the oil pump slot is, turn the slot to be where you need it, then stick the distributor in. Again, since the gears are helical, the rotor is going to turn a few degrees when you stick it in. This doesn't really change anything; you just need to know where the rotor is pointing once you get the dist all the way in, and then make sure temrinal #1 on the cap lines up.
One last important detail to handle when you install the distributor: make sure the dist shaft is not bottoming out when it's all the way in. This means that there should be some up and down play in the shaft so that it doesn't bind up with the camshaft gear. This is easy to check: When the dist is all the way in, you should be able to pull up on the rotor and feel it pull and down up a bit. THe DUI instructions advise you to do this check WITHOUT the gasket. Then when you install the gasket, that buys you even a bit more clearance. The directions also advise to use shims if you don't have any play here.
Once you get TDC, get the dist in, get the cap on, then you can proceed on:
I gapped my new plugs to .045 per Jeephammer's reccomendation, installed them, and then ran the plug wires to the dist using in this order:
The wiring portion of the job was pretty simple. I soldered my 12 gauge wire to the aforementioned connector that Jeephammer reccomended, and soldered one of the DUI connectors to the other end. I ran my tach wire to the other DUI connector. I removed the old igntion module (silver box), coil, horseshoe connector, and some of the associated wiring.
Finally, I re-worked the vacuum lines by routing the DUI to the manifold vacuum and capping off the ported vac that was used previously.
Oh, then hook up the timing light and set it to maybe 8*. You will need to do this, because the chopstick method of finding TDC isn't super accurate.
After all of this, I fired her up again and it worked! What a relief.
So, after the expense and the work, how does it run? I've never had major problems with my 258. The upgrades I've done in the last year (Nutter, Team Rush, Carter BBD rebuild, MC2100, etc) have always given me small or medium, noticeable, good benefits. The DUI gives me a slightly quicker engine start. It also lets the engine rev higher, but the one HUGE
difference is one I never expected: My Jeep will now has an incredible amount of power at freeway speeds. It's never run this good. I can get it up to 45 MPH quickly, and take it from there to 65 MPH like a modern vehicle. Before the DUI, it would take over a minute to get from 45 to 65, and now it's doing it in about 15 seconds.
This new found power at freeway speeds really changes what I can do with the Jeep. It will now be a lot easier to drive longer distances because it's just more responsive at fast speeds and just feels like it's running right.