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CFI and dual exhaust-will it run too lean?

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    CFI and dual exhaust-will it run too lean?

    I want to run dual exhaust on my 85 Grand Marquis, but I thought I remember reading somewhere that there were issues with lean conditions after that. So who has done it successfully? And would you relate your experiences please?

    #2
    it will work fine as long as you keep the cast iron manifolds or you use 90 town car manifolds or stock mustang shorty headers.
    2" would be the best size for a stock engine

    1986 lincoln towncar signature series. 5.0 HO with thumper performance ported e7 heads, 1.7 roller rockers, warm air intake, 65mm throttle body, 1/2" intake spacer, ported intakes, 3.73 rear with trac lock, 98-02 front brake conversion, 92-97 rear disc conversion, 1" rear swaybar, 1 3/16" front swaybar, 16" wheels and tires, loud ass stereo system, badass cb, best time to date 15.94 at 87 mph. lots of mods in the works 221.8 rwhp 278 rwt
    2006 Lincoln Town Car Signature. Stock for now
    1989 Ford F-250 4x4 much much more to come, sefi converted so far.
    1986 Toyota pickup with LSC wheels and 225/60/16 tires.
    2008 Hyundai Elantra future Revcon toad
    1987 TriBurner and 1986 Alaska stokers keeping me warm. (and some pesky oil heat)

    please be patient, rebuilding an empire!

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      #3
      I am for sure keeping the manifolds. Do you think the fuel pressure regulator will need adjusted?

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        #4
        Nothing will need adjusting if you're not changing the headers. The computer should be able to compensate for dual exaust without issue. If you're doing a cat-back setup (remove the Y pipe, put in H-pipe and driver side muffler/tail)... then you're fine without any tuning.

        Only two things are infinite, the universe and human stupidity, and I'm not sure about the former. -- Albert Einstein
        rides: 93 Crown Vic LX (The Red Velvet Cake), 2000 Crown Vic base model (Sandy), 2003 Expedition (the vacation beast)
        Originally posted by gadget73
        ... and it should all work like magic and unicorns and stuff.
        Originally posted by dmccaig
        Overhead, some poor bastards are flying in airplanes.

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          #5
          My '84 CV was converted to duals way back in the late 80's by my Dad and it remains like that today with over 400K on it. Stock exhaust manifolds/pipes used. No issues, so go for it.
          These are highly engineered precision vehicles, the first step in diagnosing the problem is to strike the suspected offending part sharply and repeatedly with a blunt object, then re-test.

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            #6
            Cool beans! So I can still get the OE walker tail pipes on Ebay. Does anyone know the part number for the original Walker H-pipe? It shows it in their catalog, but I think it is obsolete; because there is no current part number.

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              #7
              Like others have said, it'll be fine. Dual exhaust was an option from the factory. I put duals on my '85 CFI car and it was fine, not to mention someone deleted the cats before I bought it.
              1985 LTD Crown Victoria - SOLD
              1988 Town Car Signature - Current Party Barge

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                #8
                You can use a newer 92-94 H-pipe no problems.
                1990 Country Squire - weekend cruiser, next project
                1988 Crown Vic LTD Wagon - waiting in the wings

                GMN Box Panther History
                Box Panther Horsepower and Torque Ratings
                Box Panther Production Numbers

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                  #9
                  The ECM doesn't care what you're running past the O2 sensors.

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                    #10
                    the heads and intake can't move enough extra air for dual exhaust to make it run lean anyway.
                    86 Lincoln Town Car (Galactica).
                    5.0 HO, CompCams XE258,Scorpion 1.72 roller rockers, 3.55 K code rear, tow package, BHPerformance ported E7 heads, Tmoss Explorer intake, 65mm throttle body, Hedman 1 5/8" headers, 2.5" dual exhaust, ASP underdrive pulley

                    91 Lincoln Mark VII LSC grandpa spec white and cranberry

                    1984 Lincoln Continental TurboDiesel - rolls coal

                    Originally posted by phayzer5
                    I drive a Lincoln. I can't be bothered to shift like the peasants and rabble rousers

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                      #11
                      Originally posted by 86VickyLX View Post
                      The ECM doesn't care what you're running past the O2 sensors.
                      Kinda sorta...it has long been rumoured/reported that EEC-IV CFI throws a lean code after dramatically improving exhaust flow, after the heads.

                      There are all sorts of reasons why that might happen and they basically all come back to a design that doesn't scale well, and that's kind of whatever.

                      I never did check mine for codes after going dual...

                      OP: the correct direct-fit H pipe is a Walker 40483. It is kind of hard to find now, but RockAuto just started indicating they can get it again, with a delay, which probably means it's built to order by Walker. The price isn't pretty compared to what they used to be, either. The box Lincoln one is 40492 - it's longer because the Lincolns are longer. It won't fit at the muffler end without some hackery, but depending on what you're running for mufflers, it might be easy to make fit.

                      Reports that you can use an Aero H-pipe are something I tried to figure out some time back and the answer looked like it was probably no, because the exit pipes on the cats were not positioned quite right. I'd love to know with 100% certainty that they'll fit if that's the case.
                      Last edited by kishy; 12-23-2019, 01:53 PM.

                      Current driver: Ranger
                      Panthers: 83 GM 2dr | 84 TC | 85 CS
                      | 88 TC | 91 GM
                      Not Panthers: 85 Ranger | Ranger trailer | 91 Acclaim | 05 Focus
                      Gone: 97 CV | 83 TC | 04 Focus | 86 GM
                      | Junkyards

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                        #12
                        Thank you for that info and the part number! After doing a bit of research, I learned that AP Exhaust still makes an h-pipe for it. Their part number is 93950. Has anyone used this kit? https://www.macautoparts.net/80-88-f...st-super-turbo

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                          #13
                          The kit looks like exactly what I wanted to do, but it seems a little pricey. I am tempted though. It would be nice to just put it together in my own shop.

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                            #14
                            As long as your existing muffler and tail pipe are in good condition you could always buy just the h pipe, muffler and drivers side tail pipe and save some money. The only issue you’ll run into is finding a way to hang the tail pipe on the drivers side. The original part is long since discontinued and even the alternate bracket with the hook and rubber hanger has been out of production for years. Now if you took it to a shop they could fab something up no problem.


                            Sent from my iPhone using Tapatalk

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                              #15
                              I think I am going to just have to take it to a muffler shop anyway. I finally crawled under it and looked around. Someone cut off the factory flanges behind the cats and welded up a new y pipe, so just bolting up the oe duals is out of the question. Does anyone know if I can remove the cats without any ill affects? I wouldn't normally do this, but the air tube coming from the air pump is rusted off at the cat. I wouldn't mind just getting rid of the whole air system and the cats if I could. I thought I had read somewhere that if you had a one-wire non-heated oxygen sensor, removing the cats would make it fail to work correctly because of the lack of heat. Anyone know?

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