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Would this work?

Discussion in 'Repairs, Maintenance, Help' started by Diplomatic, May 10, 2014.

  1. Diplomatic

    Diplomatic Member

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    I've decided to do a lean burn delete. I think some of my woes come from the 29 year old computer system. There is a mixture solenoid that I think is going bad, because it wants to idle up and down every 10-15 seconds.

    I'm going to change the carb to the Holley non-computer 6280, and according to the seller, this is a "ready to run" distributor, that doesn't require the "orange box" ignition control module.

    This would be cheaper than spending 150 on the "kit" that contains the orange box. Thing is, would it work?
     
  2. KOG

    KOG KOG
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    This is the Diplomat with a 318 referenced above. You can switch to any stock electronic (non lean burn) distributor, but I would strongly suggest a '73 model as this was the first electronic model and the last to have a "normal" advance curve not hobbled by later NOX emission requirements. Thers's no need for an orange box, any later four pin amplifier such as one for an '81 truck will be fine. A '73 model carb will work fine with this combination as well.
     
  3. Diplomatic

    Diplomatic Member

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    The 73 uses a carter BBD which I've heard is kind of a joke. I wonder if switching to a thermoquad would net me better mpg?
     
  4. KOG

    KOG KOG
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    BBDs work fine. Any spread bore four barrel will, in theory, give you slightly better mileage. But not nearly enough to repay the cost of the carb and manifold.
     
  5. Diplomatic

    Diplomatic Member

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    Would the bbd hook up OK? Idk if.the choke thermostat would fit it .
     
  6. Diplomatic

    Diplomatic Member

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    The car has a voltage regulator that ties into the alternator, and the supposedly the distro, can the new distro's 12volt run off of any 12v source?
     
  7. KOG

    KOG KOG
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  8. Diplomatic

    Diplomatic Member

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    Since the egr used to go to a solenoid, can it just hook to a vacuum? What does the delay valve do?
     
  9. Bob Lincoln

    Bob Lincoln "CHECK FAULT CODES"
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    The EGR solenoid modulates (adjusts) how much exhaust gas is fed back into the intake. So you do need it for the EGR to work.

    The delay valve (I think you mean the vacuum delay valve to the distributor's vacuum advance, was used to delay spark advance to control NOx emissions. Some were controlled by a timer, some were activated only when the coolant temperature reached normal. I'm not sure of the system that your car has.
     
  10. Diplomatic

    Diplomatic Member

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    I know. Thing is, I got rid of the computer. Although it survived 29 years, I can't see a component that sits so close to the engine lasting much longer. The car won't run without it, so I don't want to stall out on the free way with a bad one.

    Ford had a major issue with it's TFI (thin film) system causing cars to cut out on the free way. Modern stuff is ok because the computer is usually in the interior.

    The computer ran the solenoids to the EGR and the vapor canister. I am retrofitting a non-feedback carburetor on it. I may loose 2 mpg, but it's safe insurance eliminating a 29 year old computer part.

    According to earlier diagrams, the EGR valve fed into a coolant vacuum switch on the manifold. I have the same switch in the same spot, but on my car it runs the vapor canister, which is soon next to go.

    I would assume I can plumb the EGR valve to that switch and then another hose to the EGR fitting on the carb.
     
  11. Bob Lincoln

    Bob Lincoln "CHECK FAULT CODES"
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    I think all of these changes are not only going to result in worse performance, but make it a lot harder to diagnose.

    Cars today still have an underhood computer that controls ignition and fuel systems.
     
  12. Diplomatic

    Diplomatic Member

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    Doubt it, lean burn didn't came out in until 1976, I've been to many car shows and cars from the model T to the '72 duster all seem to run pretty good to me.

    The lean burn system is kind of an add on, as it doesn't infest the wiring as much as the modern EEC-IV and OBD II systems do. The oil pressure sensor and coolant temp sensor go directly into the gauges versus modern cars where it goes into the computer and in turn, the computer moves the gauges. I spent several hours tracing the wiring to make sure removing the harness for the lean burn didn't mess up the gauges for oil pressure and temp sensor, didn't tie into the electric choke, alternator, coil, voltage regulator and other electrical components.

    The lean burn system is a rather "dumb" computer because it doesn't even have a CEL (check engine light) or a diagnostics port.

    My neighbor used to work for a ford-dodge dealer years ago and he told me that the lean burn system was such a pain to work on, some of the most seasoned mechanics couldn't even figure it out, and some went as far as removing it and converting it back to the mopar orange box (ECU).
     
  13. Rickorino

    Rickorino Well-Known Member

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    Unfortunately, the Lean Burn was often misunderstood and blamed for problems. People who weren't familiar with it often blamed it for problems and replaced it when something else was at fault. It is not that complicated of a system if you do your homework. I have seen many of these systems run worse and gas mileage suffered after a labotomy. Peformance gains did not offset the effort.
     
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  14. KOG

    KOG KOG
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    Removing the vapor canister will result in no improvement in any type of engine performance.
     
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  15. valiant67

    valiant67 Rich Corinthian Leather
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    I have a 1981 Dodge Mirada that still runs fine on the original Lean Burn system.
    So did the 1989 Chrysler Fifth Avenue I sold maybe 4 years ago. It was my daily driver and it ran smoothly and efficiently easily passing the emission tests here in Georgia.
    By the way, both those cars appear to have the original air cleaner mounted spark computers - no issues there.
    Yes, the computers can fail but most of the problems I've seen recently are related to the carb, not the computerized ignition. Carbs and modern gas don't get along well, no matter if the car is Lean Burn or not. Of course, swapping out the Lean Burn means a new carb is used so the carb problem is fixed when the Lean Burn is removed.

    The Lean Burn go some bad press when new because the electronic components did not hold up well. That hasn't been an issue for decades. More of an issue now is the lack of quality orange boxes in the Mopar electronic ignition conversion kits.

    Having been driving and fixing these cars since new, here are my predictions on the swap if done properly:
    1) The car will feel faster. The regular electronic ignition will advance the timing faster than the old Lean Burn system.
    2) MPG will go down slightly over a properly working Lean Burn system. if the system was hacked up or the carb was bad at the time of the conversion you may see MPG increase replacing bad parts with good parts. But MPG would go up more fixing the LEan Burn system.
    3) The car probably won't pass emissions, though now that isn't likely to be an issue as most quit testing at 25 years. I tried to get my 1988 Plymouth Gran Fury through with the converted electronic ignition on it and had no luck. I fouund a cash for clunkers car and got the computer, carb and distributor from it. I installed them as is and sailed though the emission test.
     
  16. mopar56

    mopar56 Active Member

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    so I have been following along in this thread and it seems clear that no one is in favour of the swap, now I realize from the very first post that you said you wernt looking to hot rod the car but some times simpler is better, many years ago I owned a 78 Lebaron 318 factory four barrel lean burn car, the lean burn computer did fail and I went to the dealer in my town purchased what was then know as a " Direct Connection", ( now known as Mopar Performance ) conversion kit,..orange box, new distributor, new ign module, and a wire harness, installed it in a couple hours, never changed the carb, the car never ran so good!, no noticeable fuel economy drop, in 81 I purchased a brand new Dodge truck, 318, after the one year warrenty was up, I installed a 360 cast iron intake, blocked off the egr valve with a plate, installed a thermoquad carb, while the intake was being swapped I put on a set of 273 Commando heads, again the truck was a rocket, no noticable fuel economy loss unless my foot was in it, no running issues, no emmissions left on the truck, I wonder how much being posted is speculation and how much is fact?
     
  17. Diplomatic

    Diplomatic Member

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    How can you change the lean burn without changing the carb? The lean burn is hooked to a mixture control solenoid, at least it is on this carb.
     
  18. mopar56

    mopar56 Active Member

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    well I dont remember that carb having one, this was a four barrel TQ, maybe different from yours ?, Canadian model ?, just swapped the dist, orange box, and harness, ran like a champ, dont remember messing with a solinoid, that was 25 years ago though
     
  19. ImperialCrown

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    The electronic carburetor fuel control solenoid and O2 sensor feedback system came in 1981 (California was 1980). Before that, Lean Burn was just an electronic spark advance with a specially calibrated carburetor.
     
  20. KOG

    KOG KOG
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    And the lean burn carbs had no vacuum tap for advance, a real problem when converting to normal distributor, forcing you to swap carb for a normal model.
     

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