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    #1

    Exhaust Backfire

    Does this happen to EFI lopos? I was on my way home from job #1 and as I came off the parkway, I downshifted out of OD into 3rd at 50 mph. It did one sorta loud pop and two lower pops. I've downshifted B4 and driven down the street in first (letting off at 25 mph) and this never happened. I figure that the H-pipe and EFI prevents this from happening. Is something getting ready to let go or is this just a fluke of some sort. I don't really care if it's just a fluke, I kinda like it like that.



    Packman
    Tags: None
    #2
    what kind of exhaust are you running. is it stock? does it have cats? my buddys mustang does that when he downshifts since he has no mufflers but he still has all the cats. hes got no h pipe though

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      #3
      BBk Mustang headers, cat'd H-pipe, and a 2.5" Impala catback. My Malibu used to do that, but it was carb'd and most carb'd cars do that. Also cars with true duals like your buddy's Mustang will do that. But EFI lopos, IDK.


      Packman

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        #4
        usually a sign of being rich
        Builder/Owner of Badass Panther Wagons

        Busy maintaining a fleet of Fords

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          #5
          A little off topic but a few guys out there might get a kick out of this. If you have and old carb'd 5-speed car cruise down the road 30-45 mph and shut off the engine while leaving it in gear. Wait a few seconds then turn the ignition back on. You will get the biggest backfire you've even seen. Of course its best with no cats and a good flowing or no muffler. I don't suggest doing this to a nice vehicle though. Works great when someone is tailgating you.
          Sorry for the thread jack it just reminded me of old times.
          1984 CV tudor 351W, 4bbl, 5-speed best time in the 1/8 8.39 at 80 with 1.80 60ft time.
          2006 P71, 1988 Bronco II, 1986 Baby LTD(5.0 & T5 swap in progress), 1976 16' Hobie Cat, 12' AquaFinn
          http://www.cardomain.com/ride/2651997 UPDATED 20100826
          sigpic

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            #6
            Ehaust leaks can do that too, but yeah usually it means its rich and building up fuel in the pipes.
            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

            Everything looks like voodoo if you don't understand how it works

            Comment

              #7
              Originally posted by Pesty351 View Post
              A little off topic but a few guys out there might get a kick out of this. If you have and old carb'd 5-speed car cruise down the road 30-45 mph and shut off the engine while leaving it in gear. Wait a few seconds then turn the ignition back on. You will get the biggest backfire you've even seen. Of course its best with no cats and a good flowing or no muffler. I don't suggest doing this to a nice vehicle though. Works great when someone is tailgating you.
              Sorry for the thread jack it just reminded me of old times.

              A friend of mine did that in his old overcammed Buick Century. There was this one stretch of the main road where the kids used to walk down and hang out. He would shut the ignition off about half a block away from a crowd of kids and then turn it on right as he passed. Had to have scared the piss outta them, literally. After replacing the exhaust system twice (explosions in the exhaust tend to break things) we called it quits.

              Running rich. Hopefully that was a one-time event, unless I can somehow tune the stock speed density.



              Packman

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                #8
                I had an old work truck that would bang every now and again. It might go months without doing it, but then it would sort of stumble for a bit, backfire once and then it would be alright for a long time.

                My favorite was some lady in a red BMW (or was it a Saab? I forget...) with the window rolled down. She was just about even with the end of the tailpipe when it went off. I knew it was coming, and let up on the gas, but it let one loose anyway.

                KABOOM!

                She swerved all over the place and just about lost her phone out the window. Man, did I ever get a nasty look out of that one.
                Owner of the only known 5 speed box wagon with a lift kit.
                AKA, Herkimer the Hillbilly SUV.



                Axle codes
                Open/Lock/Ratio #
                -----------------------
                G / H / 2.26
                B / C / 2.47
                8 / M / 2.73
                7 / - / 3.07
                Y / Z / 3.08
                4 / D / 3.42
                F / R / 3.45
                5 / E / 3.27
                6 / W / 3.73
                2 / K / 3.55
                A / - / 3.63
                J / - / 3.85

                Comment

                  #9
                  Originally posted by Pesty351 View Post
                  A little off topic but a few guys out there might get a kick out of this. If you have and old carb'd 5-speed car cruise down the road 30-45 mph and shut off the engine while leaving it in gear. Wait a few seconds then turn the ignition back on. You will get the biggest backfire you've even seen. Of course its best with no cats and a good flowing or no muffler. I don't suggest doing this to a nice vehicle though. Works great when someone is tailgating you.
                  Sorry for the thread jack it just reminded me of old times.

                  nice I read this somewhere before but forgot about it.. just be careful cuz i heard it can blow your muffler apart
                  Give a man a fish and he will be fed for a day. Teach a man to fish and he will promptly forget that he once did not know, and proceed to call anyone who asks, a n00b and flame them on the boards for being stupid.

                  Comment

                    #10
                    Originally posted by GoodSamaritan View Post
                    My favorite was some lady in a red BMW (or was it a Saab? I forget...) with the window rolled down. She was just about even with the end of the tailpipe when it went off. I knew it was coming, and let up on the gas, but it let one loose anyway.

                    KABOOM!

                    She swerved all over the place and just about lost her phone out the window. Man, did I ever get a nasty look out of that one.

                    Probably didn't help things to be laughing and pointing at her when she finally caught up to you.:evil:




                    Packman

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                      #11
                      have you seen the movie uncle buck? it would be so kool to have a car backfire like that haha. mine does it once and a while (little pops) but pretty much solved itself and i wouldn't worry about it. Carbed could more likely be running to rich, but EFI is safer bet that its nothing much to worry about sometimes little hickups happen haha.
                      Finally have an on the books porting/custom fab business!
                      HO bottom end,GT40Ps,cut/welded/ported upper+lower GT40 intakes,Comp XE258 cam,MS3X megasquirt computer,8 LS2 coils,2 dry systems + a 3rd wet,3 core rad w fans..1100hp Lentech WR AOD,custom 4" aluminum/moly Dshaft,custom rear/back half chassis adjustable 4link,wilwood 4 piston,moser 9" axles,locker, M/T 30x12's,4 staged fuel pumps,100lbs sound insulation,power/remote everything,2000W sound.4480lbs. 4.5s 0-60,12.8 1/4

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                        #12
                        Originally posted by cld783 View Post
                        nice I read this somewhere before but forgot about it.. just be careful cuz i heard it can blow your muffler apart
                        This is why I mentioned having practically no exhaust system. My buddy tried it in his 82 s-10 a blew the muffler in to a million pieces. It was still cool though.
                        1984 CV tudor 351W, 4bbl, 5-speed best time in the 1/8 8.39 at 80 with 1.80 60ft time.
                        2006 P71, 1988 Bronco II, 1986 Baby LTD(5.0 & T5 swap in progress), 1976 16' Hobie Cat, 12' AquaFinn
                        http://www.cardomain.com/ride/2651997 UPDATED 20100826
                        sigpic

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                          #13
                          I have done that in my dad's old station wagon, but thats an automatic and the NSS has been disabled.

                          There used to be this landclearing place next door to my dad's that had an '87 F250 2WD. It was a 351 4 bbl, C6, etc. It had those strange dual tailpipes that come out next to each other (I've always thought that was peculiar on those trucks). Anyway, that thing would backfire when you let off on the gas... religiously. Anywhere more than half throttle, when you let off quickly, it would do it. And it was LOUD...

                          Incidentally, my dad used to service AT&T trucks of the same era, and they used to blow the front portion of the exhaust apart all the time. That and melting converters...
                          **2012 Ford Mustang Boss 302: 5.0/ 6 spd/ 3.73s, 20K Cruiser
                          **2006 MGM,"Ultimate": 4.6/ 2.73/ Dark Tint, Magnaflows, 19s, 115K Daily Driver
                          **2012 Harley Davidson Wide Glide (FXDWG):103/ Cobra Speedsters/ Cosmetics, 9K Poseur HD Rider
                          **1976 Ford F-150 4WD: 360, 4 spd, 3.50s, factory A/C, 4" lift, Bilsteins, US Indy Mags, 35s Truck Duties

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                            #14
                            Had an 87 F250 at the marina that would blow fireballs out the tailpipe if you revved it. Going down the road it was like random small arms fire. I removed all the pollution control shit, and the problem went away completely. I suspect it was one of the smog pumps not bypassing and pumping air in all the time, but I never really diagnosed it beyond the fact someone had extensively butchered the vacuum plumbing.
                            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

                            Everything looks like voodoo if you don't understand how it works

                            Comment

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