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bosco0104's avatar
bosco0104
Explorer
May 22, 2013

Failed Smog Test

I have 1985 Class C Ford E350 with a 460 carberated engine. I just had the carb rebuilt and it is now running like a top. Carb is a Holley 4180 I believe. Problem is it failed its smog test today. I have turned a few wrenches and even rebuilt a motor or two but I am not good at diagnosing these types of problems. I have searched the web and forums for ideas and now I am turning to my fellow RVers. It did not pass the HC Test. The HC readings were 950 first idle and 1000 second test idle after reving the engine. Passing is 350. Where should I start? Should I lean out the air/ fuel idle mixture? If so how much? 1/2 turn ? 1/4 turn? I will check the timing but I am not sure about the dura spark distributior on it. Do I check it like a regular distributoir for time? Can it be the EGR valve? I just hate to throw parts at something without knowing whats wrong. Thanks for any help that you may have.
Class C
  • carringb's avatar
    carringb
    Explorer
    May 22, 2013
    Its definitely carb tuning. If its tuned right it will pass no problem. My old boss always used a cylinder balance analyzer for tuning. You can also use a wide-band O2 sensor. You could just try small changes on your own (lean it out), and just keep going back to DEQ for a free air-check (you don't have to do ay paperwork if you ask for the free air-check) until it passes.

    The good thing about this all is you will stop wasting extra fuel once you get it tuned right. I just realized yesterday how big of a jump fuel prices made again:E
  • jdog's avatar
    jdog
    Explorer
    May 22, 2013
    Not a lot of people here with a FORD 460 motor in a motorhome. Seems like everybody I know with a 460 motor in something has problems with the carb. The original can't be replace, so something else has to used. You might have to go to a smog repair shop to have it tuned or de-tuned for smog. If you start changing the vacuum valves or jets, you could easily get too lean causing more problems. New standards for older motors do not help your motor at all. Good luck.

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