Dual exhaust on a 368 w/ DFI
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500, 472, 425, 368 Discussion, Dual exhaust on a 368 w/ DFI in Cadillac Engine Technical Discussion; I recently got a 1980 Seville(w/ the 368) for free. The guy just wanted it out of his driveway. The ...
  1. #1
    tmoore8828 is offline Cadillac Owners Member
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    Dual exhaust on a 368 w/ DFI

    I recently got a 1980 Seville(w/ the 368) for free. The guy just wanted it out of his driveway. The car fired up as soon as I charged the battery. I did all the basics, oil change, plugs, cap/rotor, wires, transmission fluid, fuel filter etc... The car ran, but pretty poorly. I ran the diagnostics and determined the computer was dead. I replaced the computer ($102 for a reman) and it was the difference between night and day! Now for the question. The stock exhaust is shot from the Cat back. I have a friend that specializes in custom exhausts. How would the computer react to a true dual exhaust with an x or H pipe. I did some searching on the sight and read some posts where people stated the stock fuel system pressure was too low to keep the engine from leaning out. What do you guys think? Thanks in advance Tom

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  3. #2
    TorqueInc's Avatar
    TorqueInc is offline Cadillac Owners Member
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    Re: Dual exhaust on a 368 w/ DFI

    a dual exhaust will make it VERY lean...its been done

  4. #3
    tmoore8828 is offline Cadillac Owners Member
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    Re: Dual exhaust on a 368 w/ DFI

    Is there any way to avoid the lean condition??

  5. #4
    TorqueInc's Avatar
    TorqueInc is offline Cadillac Owners Member
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    Re: Dual exhaust on a 368 w/ DFI

    Not that im aware of i havent messed with the factory FI systems enough to have a fix.

  6. #5
    maybelline is offline Cadillac Owners Member
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    Re: Dual exhaust on a 368 w/ DFI

    Just to add to the knowledge base. If a person increased the fuel pressure the injectors would flow more. add an aftermarket fuel pump to boost pressure and a fuel pressure reg that operates on manifold vacuum (like from FAST.) and you have a pretty simple solution to the problem. I don't know much about this particular engine but i assume it has an O2 sensor. If it does, the computer will be able to handle the added flow with no problem.

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    Just to add to the knowledge base. If a person increased the fuel pressure the injectors would flow more. add an aftermarket fuel pump to boost pressure and a fuel pressure reg that operates on manifold vacuum (like from FAST.) and you have a pretty simple solution to the problem. I don't know much about this particular engine but i assume it has an O2 sensor. If it does, the computer will be able to handle the added flow with no problem.

  7. #6
    BRUCE ROE is offline Cadillac Owners Fanatic
    Automobile(s): Eldorado
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    Dual exhaust on a 368 w/ DFI

    I don't think duals will hurt much; don't expect spectacular performance.
    I believe the car has an OX sensor which will compensate automatically.
    Bruce Roe

  8. #7
    drmenard is offline Cadillac Owners Enthusiast
    Automobile(s): 95 fleetwood 81 deville
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    Re: Dual exhaust on a 368 w/ DFI

    I had a DFI 368 that I put on 425 exhaust manifolds and Y pipe and cat on... The rest was stock. It made a big difference and I had no problems... If I thought it was running a little lean I would just adjust the fuel pressure regulater up a few lbs...I bet, like Bruce said, the O2 sensor will take care of it...

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