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Thread: black smoke

  1. #1
    Junior Member APPRENTICE
    Join Date
    Jan 2004
    Location
    South Dakota
    Posts
    18

    black smoke

    having problem with tow rig. 350 chevy engine, single plane intake (i know its not perfered for towing) holley 600cfm with vac. secondaries manual choke, in a 74 gmc 4speed manual. Had same problem with 750 vac. secondary, this 600 carb came off a good running 454 about a year ago Smokes black while driving, could this be a power valve problem
    ? Vac. advance seems to be working, choke is off. any advise appreciated.
    Ryan

  2. #2
    Senior Member MASTER BUILDER
    Join Date
    Nov 2007
    Location
    Wisconsin cheesehead!!
    Posts
    213
    could be the power valve if it smokes after a certain vacume is achieved. otherwise I would think going from a 454 to a 350 you will probably have to downsize the jets a little. Im thinking the BB needed a little more fuel.

    what model carb is it?

    I have a dual plane SBC wieland stealth mani sitting in my garage if you want one. I dont have any need for it right now.
    1987 Pontiac Fiero GT
    418ci SBC v8, manual 5-speed.
    dual stage nitrous injected

  3. #3
    Junior Member APPRENTICE
    Join Date
    Jan 2004
    Location
    South Dakota
    Posts
    18
    the carb is 1850-2 and has factory 66 primary jetting in it, pv holds vac. but will i nstall a new one anyway and see if it helps.

  4. #4
    Senior Member MASTER BUILDER
    Join Date
    Oct 2003
    Posts
    144
    350 cubic inch motor would create a higher vacume rate than a 454 due tot he restricted cubic size, thus the fuel is just being pulled out of the bolsters. try downjetting from 66 to possibly 60 then try it out.


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