melting DUI - updated july '07

[falcon fanatic]

I have my head off to install my new head (if the machininst ever finishes it :roll and I decided to check my TDC marking, so I plulled my distributor cap off to make sure I was at TDC and not BDC and discovered that my cap and rotor where melting! all around the center electrode on the rotor the plastic is melted, sending splatters everywhere. The cap is similarly melted and I don't remeber whether there was an electrode extedning down from the coil, but it there was, it's gone. Remarkabley, the car ran fine like that. A testament to the power of the system. The assembly will be shipped for evaluation by Perfomrance Distributors tomorrow.

 

[rbohm]

8) sounds like a bad coil to me.

 

[fordconvert]

If its like the stock setup the center contact drops in and has a flange that keeps it from falling in and a spring crimped onto it. The next part is a large rubber washer that pushes on the flange to hold it down and must act somewhat as a damper to keep the coil tight. The coil then goes in with the 4 screws. That little mushey spring is all that contacts the coil. Was the rotor nice and tight? I had a rotor that came loose one time and made a huge mess but still ran. Other thing I have seen is someone puts the rubber washer in first then the contact assy. THe contact does not stick out far enough to touch the rotor and it doesnt last very long. This is the way the stock ones are Im not sure if DUI does anything differnt or special.

 

[jamyers]

Sorry to say it, but overheating coils is a "feature" of the GM epoxy-filled-coil-in-cap HEI design. If any of the above-mentioned rubber washer / contact spring / etc isn't right, or if you operate around/above 4K rpm for very long, the coil will get extremely hot (relative to a nice oil-filled coil).

I don't know if DUI did anything to help, but it's kind of a design flaw in an otherwise perfect setup.

I wonder if DUI makes a remote-coil dizzy? Prolly not, because then you'd lose the 1-wire feature.

 

[shmoozo]

I wonder if DUI makes a remote-coil dizzy? Prolly not, because then you'd lose the 1-wire feature.

Evidently they do, but not for the "small block" six.

"Big block" six, yes.

V6s, yes.

V8s, yes. (duh!)

"Small block" six? Apparently not (unless one of the models for one of the other six cylinder engines will work), though I have no idea why not.

--> Link HERE

 

[falcon fanatic]

Well, it would'nt be the Davis Unified Ignition if the coil where not part of it. As for assembly, well I never took the cap apart. Just looked inside, installed it, and set the timing.

I'm surprised to hear that they overheat with sustained driving over 4000rpm. That seems a bit silly for a high performance ignition. At any rate, since my power band peaks at about that speed (and I'd be going 90 on the highway - scaaaarrry in the rust bucket ) That's certainly not the cause. Still, overheated coil it is as the coil was all covered in grey soot.

With my new head and rocker assembly I'll be able to hit 5000rpm and more with no problems, so I hope the replacement unit holds up...

 

[falcon fanatic]

It seems like a nice, finned aluminum heat sink directly on the coil would make a big difference.

 

[falcon fanatic]

So, some of you will recall that when I first installed my DUI, I was having massive EMI. I put noise filers in my radio wiring, I upgraded my ignition wires. All to no avail. A word to the wise: If you are having this problem, inspect your ignition meticulously. My coil was shorted out, causing the emi, and eventually melting the cap and rotor and coil.

Once I got my repaired unit back, the problem went away entirely.

 

[66 E100 Pickup]

If you are having this problem, inspect your ignition meticulously. My coil was shorted out, causing the emi, and eventually melting the cap and rotor and coil.

Could anyone tell what part was shorted out? Bad wire connection?

I am very curious whether this unit would hold up inside a 66 econoline doghouse with it's big time heat issues...

John

 

[rbohm]

8) it was the ignition coil that shorted out.

 

[66 E100 Pickup]

it was the ignition coil that shorted out.

well ya...that isn't going to show up though with meticulous visual inspection, and presumably Davis checked the coil out before sending it off. It sounds more like the connections as it ran for a long time while it slowly melted...

John

 

[Lazy JW]

....

I am very curious whether this unit would hold up inside a 66 econoline doghouse with it's big time heat issues...

John

Those DUI's are very large physical size, you may encounter some clearance issues inside a doghouse.
Joe

 

[66 E100 Pickup]

Those DUI's are very large physical size, you may encounter some clearance issues inside a doghouse.

this one is my 200 econoline. Lots of room. In fact, bringing the new dizzy up about 5" will make it a lot easier to work on (lol the intention is to never work on it again ).

I've got to get this one reliable before I can use it to haul my 240 block to the machinist .

John

 

[AzCoupe]

More than likely, it was just a faulty coil. I doubt it had anything to do with heat. Heck, it may have even been my fault? If I changed the cap color prior to shipping, I may have installed the wire ends improperly and shorted it out? I've shipped a lot of these, and only two have had issues. However, both were covered by the manufacturer. If your worried about reliability, carry a spare cap/coil in the trunk, which can be purchased at any parts store. Its a lot cheaper to carry a spare cap/coil, than a Petronics, or MSD box.

 

[AZstang66]

No quams on mine. I drive at high RPMs and it holds up great!