Running very rich & black smoke when I nail it

Discussion in 'The Mixing shop.' started by rkammer, Aug 15, 2015.

  1. rkammer

    rkammer '71 GS455 Arctic White

    I'm posting this here 'cause I believe my problem starts with the carb. Whenever I nail it I get black smoke out of the tailpipes big time. And, just to see what kind of fuel mileage I'm getting I checked it on the last tank of gas. Mileage was about 9 MPG on combination city and Highway driving (highway was averaging about 65 MPH). I'd hate to think what it might be in pure city driving. :ball:

    The basics of my combo are:

    462 with 10.6 CR (ported TA Stage 1 Aluminum heads)
    Turbo 400
    Custom Comp cam with .499 lift and 228/237 @.050
    3.55 posi gears
    10.5 in. tight converter that stalls about 2500
    800 QJet built by Mark with .074 primary jets & .042 rods. DA secondary rods with M hanger
    Dave Ray HEI in stock distributor with 13 deg initial, 20 deg centrifugal, and 10 deg vacuum advance hooked to manifold vacuum.
    Engine idles at 800 RPM with 16 in of vacuum.

    Don't get me wrong. I'm not trying to maximize fuel mileage but, I'm thinking that 9 MPG is a bit low. What are some of you getting with similiar combos? I was expecting something in 12-13 MPG range at least.
    Last edited: Aug 15, 2015
  2. rkammer

    rkammer '71 GS455 Arctic White

    Anyone like to chime in on this one? :pray:
  3. alan

    alan High-tech Dinosaur

    My first thought is maybe the primary metering rod doohickey is stuck up.
  4. rkammer

    rkammer '71 GS455 Arctic White

    You mean the power piston? I'll check it, hadn't thought about that one.
  5. Jim Rodgers

    Jim Rodgers Well-Known Member

    Check for trash in needle and seat.

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