plugged exhaust?

Mopar Exhaust Systems

  1. pishta

    pishta I know I'm right....

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    put a NOS carb on a Mazda B-2000 (hey, it could be a D50 for reference sake!) and now the car doesnt want to exceed about 50 mph. Its like a rev limiter kicks in at about 3500 rpm, I mean it lays down hard like the ignition cuts out then when I let up on the gas, itll pick right up so I limp it home doing about 1100 rpm in 4th. ITs kinda weird that I drove 140 miles round trip on the old leaky shaft carb and this didnt happen. Is it timing? too far retarded/advanced/mechanical not working? (it times dead on at 8 BTDC with a timing light and advance plugged) Itll buck if I floor it enough to think some one is turning my ignition on and off. Someone told me it may be a plugged cat or muffler, and it aint the muffler because I cut it off and it still does it! What gives? right off the bat I can rev it up but it seems to get worse after it has a chance to "load up" as the plugged cat guy explains. I dont really buy his theory but im shooting in the dark here.
     
  2. 67Dart273

    67Dart273 FABO Gold Member FABO Gold Member

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    Seems to me you.............changed the carb and the problem appeared.

    Something "in" the carb inlet/ filter / needle/ seat, etc?
     
  3. inkjunkie

    inkjunkie Well-Known Member

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    This is where I would start poking around......
     
  4. pishta

    pishta I know I'm right....

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    Hard to reason why it would run so good at idle...maybe it just a p.ugged fuel line? It has a huge fuel bowl with a big sight glass and an electric pump and every time i look at it, its full. Ill check it out. Never had a carb go lean off and on though, was hoping it was timing, just ran out of tEsting time.
     
  5. zhandfull

    zhandfull Well-Known Member

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    I had a 87 Mustang 5.0 and a 93 F450 work truck with clogged cats. They both ran just like youre saying great at idle but wouldn't run over 45 mph and were getting really lousy fuel milage.

    I would also consider the carb or fuel system as the problem since you didn't have any issues before changing it, But the cat would be next for sure. On that 93 work truck I had. It had blew a head gasket and the anti freeze in the exhaust system just destroyed the cat.
     
  6. 67Dart273

    67Dart273 FABO Gold Member FABO Gold Member

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    Your description matches things like a failing fuel pump, plugged filter, collapsing suction line, or otherwise obstruction in the fuel system. Since it sounds as if the trouble appeared right after swapping the carb, it might be something right in the carb fuel inlet area
     
  7. pishta

    pishta I know I'm right....

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    after sleeping on it, thats a great diagnosis as all the pieces fit:
    Perfect idle (low fuel consumption)
    falls flat right when the fuel bowl would become exhausted if badly restricted
    seems to recover when I let off gas (back to low consumption)
    and seems to recover randomly (fuel making it past restriction at times)
    and it has to be at the inlet, EZ one nut visability....will advise.
     
  8. Revhendo

    Revhendo Master ACME Tech

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    I know this will sound stupid, but did you change the fuel filter when you put the carb on? Is it on the right way? (Don't ask how I know). How old is your NOS carb? Is it possible that the jets are clogged and it will run on the idle/transition circuit but not through the main?
     
  9. pishta

    pishta I know I'm right....

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    carb was vacuum sealed, circa 1984. not even tarnished. old fuel filter (duh on me) never even crossed my mind. It is a clear plastic one and it looked fine last time I was back there (rear frame above leaf spring, before the electric pump)
     
  10. RustyRatRod

    RustyRatRod I was born on a Monday. Not last Monday. FABO Gold Member

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    I just eat a few good chili dogs when my exhaust gets plugged.
     
  11. pishta

    pishta I know I'm right....

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    Its dairy for me, lactose intolerant!
     
  12. pishta

    pishta I know I'm right....

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    Well, removed fuel inlet and it was clear. Removed both main jets and blew out passages and blew out all vacuum ports. Seemed to clear it up just fine. I bet my secondary was plugged. Runs great now, was able to weld my exhaust back up ( thanks for THAT advice!) And we should be good to go. New rad cap and coolant too. Wish i could isolate that 1 little valve tick, other than that im happy.
     
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