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b-dog 08-16-2013 12:57 PM

been thinking about installing a D.U.I. distributor on in my cj. last winter i replaced my 258 with a rebuilt 304. everythink went pretty good had to get a few things from the junkyard like the distributor. my rebuilt 304 had points. so i pulled a distributor from a wagoneer and used it. it was a little cruddy looking but i cleaned it up and istalled it and it ran great. with the intention of atleast replacing the cap and rotor. never got around to replacing it. my question is how much differance do you guys think it will make. worth the $400. also if i just replace the cap i was going to install the bigger cap. but it looks like a light fit with power steering pump.

JoeDahero 08-16-2013 02:00 PM

Just my $0.02 but if you're expecting a dramatic difference and your current ignition is functioning properly you'll prolly be disappointed. I put a DUI in my 304 about two years ago. Was there a difference: yes. Was it huge and immediately obvious: no. For me it was worth it to eliminate the potential problems of points but others here will tell you you can get the same results cheaper through different methods. For me it was part of a process of elimination of potential trouble areas in my motor. As I'm just a shade-tree guy, the most effective method of engine troubleshooting is deductive reasoning and process of elimination. Along with all the other things I've done to it, my 304 is a sweet-running, reliable motor. The DUI is part of that but doesn't get all the credit. Ignition is just one piece of the puzzle. Research all the options out there and decide which way to go. For me the DUI made sense and I'm happy with it.

bradleybrb 08-16-2013 02:08 PM

Just my .02 but I would go with the DUI if I was going with an hei set up. That's based off the problems I have had with a cheaper hei that I bought.

jdarg 08-16-2013 02:10 PM

There's probably bigger gains in adjusting the curve on the waggy distributor. Its a heavy vehicle and that's probably reflected by a less aggressive advance in that jy dizzy. Then drop in a used MSD box. You'll be ahead of a DUI for less money IMHO.

LSUtiger 08-16-2013 03:36 PM

Personally I thought the hei dizzy was to large for the v8. The cap is huge and it's close to the p/s belt which make adjusting the timing more difficult.

JeepHammer 08-16-2013 04:49 PM

This has been beat to death...

When you trade one factory system for another (in this case, Ford/DuraSpark for GM Clone/DUI) you are just swapping 'Issues'...

Joe hit the nail on the head,
Once you have eliminated the 'Problem' issues, both ignitions work about the same,
The difference is, the upgrade DuraSpark distributor is much easier and cheaper to do than pulling the distributor and starting over from scratch.

With Joe's situation, '74 had Prestolite or Breaker points, both sucked in a HUGE way.
Anything would have been an upgrade...
DUI was probably a viable swap for him, since he didn't have a reasonable distributor to start with.

B-dog has an '85, and that's a different story...
'85 has a DuraSpark distributor in it, and that is one of the most precise, easy to tune units on the market. VERY DURABLE, strong signal, and with a simple cap, rotor, plug wire upgrade, it will deliver high voltage as well as it manages the low voltage/timing advance.

Cap, rotor & plug wires are cheap, and need replaced every 20 or 30 years anyway! (or sooner if you want things to run correctly).

If you look in my signature line, you will find an upgrade link for the factory style ignition, and that might give you some ideas before you shell out your hard earned bucks on something you have to start from scratch with...

The choice is yours, We'll support you with either choice!

JoeDahero 08-16-2013 05:24 PM

Jeephammer- thanks for the props but for me it really came down to laziness. I read and re-read your write ups and posts on ignition and in the end it just seemed easier to spend the cash and drop in the complete DUI unit than to hunt up all the parts to do the Duraspark.

And FWIW your comments on Chinese clones and cam gears ultimately led me to spend the cash on the DUI rather than taking a chance on a cheaper setup.

The DUI was super easy for me. Did it on a Saturday afternoon and went without a hitch.

Bottom line - replace or improve or refurbish your ignition. Which ever way you go it'll be worth it. Don't expect a miracle but a bunch of little things can make a big difference all together. My 304 isn't remotely the same animal that came home on the trailer when I bought the CJ and I haven't done any major engine work or spent a ton of money.

Get it running RIGHT - then decide where to put money. Don't look for a magic bullet because there isn't one regardless of what DUI wants you to believe.

John N 08-16-2013 11:37 PM


Originally Posted by LSUtiger (Post 15802034)
Personally I thought the hei dizzy was to large for the v8. The cap is huge and it's close to the p/s belt which make adjusting the timing more difficult.

The easy solution is to a 1" to 2" longer p/s belt. There's plenty of adjustment in the pump and it'll clear fine.

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