DUI is a brand, they just repackage GM V-8 HEI ignitions and make them available for use in all kinds of vehicles. They do have some of their own components, but using a stock GM HEI where possible will yield the same result. DUI is good stuff though, great products at an appropriate price. Which is a lot.

20R and 22R distributors/complete ignitions are completely interchangable. I installed a complete 1990's era electronic system, bolt in with no mods, in my points-ignited 76 20R in about ten minutes. The vacuum advances were different but also interchangable from distributor to distributor. I don't know of compatibility amongst EFI engines and carbs, however. Very little hands on time with RE's. I can't remember offhand what the other port is for but I can tell you with 100% certainly on this and many other makes of vehicles, only one port is necessary. You're asking me to dig DEEP into an area of my brain that hasn't been used for ten years, lol. Cobwebs, cobwebs, HELP!

Negative on the timing at WOT. It's only function is to increase timing at a steady cruise and very light throttle to also increase fuel economy. Any serious performance engine with a carb cannot run vac advance since the throttle plate generally has to be open too far as to allow the ported vacuum to stay off at idle. At WOT regardless, the vacuum advance is not operational. Here's a good article for you: http://www.camaros.org/forum/index.p...ic=2680.0;wap2

WOT advance is handled by the mechanical advance in the dizzy. Vacuum advance has no vital function and any engine will make just as much HP/TQ and run just as well without it. It will only impact mileage if unused and drivability if there is a malfunction, which is pretty rare. I mean, it's a diaphragm with a lever to an advance mechanism. There just ain't much there.

The above article illustrates my frustration with 'do it just like the factory sez' mentality. The 1970's to 1980's in the US were a vacuum, heh-heh, of idiocy and sillyness concerning engine tuning. There was a lot of BS spread about what works, and an FSM will absolutely not explain to you that the factory specs aren't what's best, but what was required by the EPA and was a stop-gap effort made by OE's to comply with the fascist EPA and CARB requirements. The necessity of this LONG teething period is debatable, however it happened and we are left to deal with it. Check into DEF 4 standards for Diesels, it's happening all over again right now.

Since most folks here are not professionals but honest, well-meaning, helpful and intelligent they figure a lot of it out through trial and error. Even other professional mechanics (guys today are taught NOTHING on carbs. Why should they be? I wasn't taught about them in trade school from 2002-05) don't know this stuff because carbs are extinct except for lawn equipment and precious few motorcycle/marine applications. Don't get me started on 'spark energy' and 'plug gap.' Oy. The mysteries of the spark plug... psych.


It's harder going from modern tech to older tech than visa-versa for the professional. I say this because I work on everything, though no longer professionally. I left the industry in 2005 after a year as a Dodge tech and 4 months as a Swift Transportation shop tech. I had my first car at 13 and built an engine for it with my dad at 15. I had done other projects with him (he's a truck mechanic to this day, engines mainly.) before then and even by trade school time I knew a lot about carbs because my car and every car I maintained for my family with my dad was also a carb with only one exception. Carbs are way more complex than EFI systems, one of the many reasons EFI is a better system. I still prefer carbs, even though they are inferior in every way I can think of at this moment. I just like old crap I guess.

On your final point, I learned long ago that I'd rather take it in the wallet than to fuss with factory carbs from the 70's and up. The Weber, contrary to popular opinion here, is not a great carb. It is exceedingly simple and easy to use. I'd probably fork over the extra cash and go Barry Grant next time, but Webers do their job and are easy to use and troubleshoot vs any 70's on factory carb I've ever seen. I try to avoid them. They really aren't that difficult, just difficult enough to justify my laziness in that regard. I had done the exact same thing as you with my 20R. Ordered the lifetime warranted stocker and I replaced it shortly after with the Weber for reasons of simplicity.

Wish I would have known you were a mechanic earlier, our conversations could have been more in depth in the past. If I ever have EFI problems you're getting a PM.

Lastly, I agree with your sentiment. This is a great community with so many DIYers who are overly generous with their time and commitment to help each other out. It is very heartwarming to encounter. There is a similar mentality on candlepower forums as well, I'm a huge flashlight geek. I very much appreciate your kind words, though I assure you I'm really just a huge dick.

edit - I just had a thought; I don't remember seeing a dashpot on the factory carbs. It's possible the second vacuum line on these could serve that type of function. Not certain, just thinking out loud, dusting off cobwebs. I have a journal around with notes upon notes all on engine tuning left over from school. If I feel motivated maybe I'll sift through it and see if I wrote anything down about it. Even though carbs weren;t covered in detail I added a lot of my own carb specific info to my notes knowing I would always be a geek.

 

That's why I went with Weber, finally. My last experience with National Carburetor wasn't good. Huge vacuum leak where the throttle bar goes through the carb. After sending it back & forth to them and getting a 15 minute lecture over the phone on all the technical tests they do so they couldn't possibly have missed anything, paying two different carb specialists who sent me home saying "I can't tune it", and National insisting it must be a problem with my truck, I bit the bullet and bought a Weber. 2 hours later, truck was driving better than it ever had.

This was all going on days before I was leaving for year long trip around the country in my truck.

 

Moroza, DUI in this case stands for Dewey Unified Ignition ( I think ). They are a company in Tennessee that will build a GM HEI type distributor to fit almost any engine made. On a 20R, they look kinda funny sticking so far out past the head and they are fairly big in diameter too. But they only require one ignition wire and one vacuum line and they put out quite a bit of voltage so it is a good upgrade from stock. Combined with E-3 plugs, a 38/38 Weber, exhaust header and complete de-smog, my 20R runs like a sewing machine and runs really clean too.

 

That would be Davis, not Dewey.

 

Jimbyjimb,
Thanks for the clarification. It's been too long since I put that DUI distributor to remember what DUI stands for. Of course, being old and senile doesn't help much either.

 

Still have to see how it handles over the next couple days, but I think I'm good.

I can tell you that it does not like 10,000 + ft elevation. I drove over Vail Pass yesterday, and it was all I could do to keep it above 40mph, floored, in 3rd gear. Going downhill slightly...

But once I got back down to the valley, probably more like 5,000ft, it had no problem going 65-70mph again. We'll see how it does over the next couple days, with some fine tuning of the carb if it seems like it needs it, and checking my timing again. Probably larger jets couldn't hurt. But we'll see.

 

Sorry I mislead you, if you are running lean at sea level, you will be running richer in gas at higher altitude since the air is less dense at altitude (less oxygen, needs less gas for a proper air/fuel ratio). I mixed things up.

 

No problem. Didn't effect what I was doing anyway. I figure I'll just go back through the Weber tuning instructions if I feel like I need to. So I'll listen to the engine, not some idea in my head of whether it should be running more rich or more lean because of my altitude.

 

When adjusting a carb for elevation the proper procedure is to increase air jet sizes, not decrease fuel jet sizes just as an FYI. You want that fuel but because the air is thinner the mix richens, as was pointed out. So increase the amount of air coming in. For brief excursions through high alt it's probably not worth messing with jetting.

In any case, these engines are grumpy at high altitude in general. They're making 90hp at the crank on a good day. The thin air makes R angry.

 

I was mostly just meaning adjusting for best lean idle again. Re-jetting will be something I'll look into when I'm staying put somewhere for the summer. But now that I'm back in mountain elevations, I figure it might need some fine tuning.