Carb 308 Smog Test

Discussion in '308/328' started by bowserrh, May 12, 2009.

  1. bowserrh

    bowserrh Rookie

    Oct 16, 2007
    Poway, CA
    Full Name:
    Robert Bowser
    Got my annual Kalifornia smog test notice for the old '78 308GTS, and duly took it down to the local Test Only station. It passed, although just barely.

    It is funny, there is a perception that these old carb cars are impossible to keep in tune and very difficult to smog successfully. I never touch the carbs, and the car has NEVER failed smog in the (almost) 12 years that I have owned it. Six biennial smog tests. Six passes. All I really do is drive it regularly. Perhaps that has something to do with it.

    In contrast, my brother has a '78 Porsche 911SC. Same year, different manufacturer. Although it is a product of German engineering, and fuel injected, it fails smog
    regularly. He has to take it to his mechanic to get the mixture adjusted so it runs like s**t, get it smogged, then return it to put the mixture back to a drivable setting.

    I think perhaps the reason my car barely passed this time is because I went back to the standard 55 idle jets. I had been using 60s. With the 60s, it seemed to run a bit better right off idle, but worse at higher throttle settings, especially when hot. The smog test has the car running at 15mph and 25mph on a dyno, which is right in the flat spot of the 55 jets. I think next time I'll put the 60s back in for the test.

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  3. Ferraripilot

    Ferraripilot F1 World Champ
    Project Master Owner

    May 10, 2006
    Full Name:
    It's man
    When these carb engines are right on to factory spec idle timing, cam timing, and carb settings then yes, they will pass. For me, I tune my engine with about 38-39degrees total timing at 5000rpm. The 2 valve engines can take more timing than that of the 4v 308 engines. The problem is this leaves idle timing at about 13 degrees which, although I have not tried it, will probably not pass CA or NV emissions. Emissions are yearly here in NV, and just to be sure I always change my oil, spark plugs, reinstall 220/135 air corrector and main carb jets, set timing to spot-on factory 7 degrees, reattach air pump belts, get it super hot and presto no emissions issues. It just worries me because the inside of my pipe tips always shows white which means it is running lean and hot (good for emissions but bad for the engine and heat).

    I guess I do this because I failed once and decided from that point on I would never go through that again. It's a good time to change the plugs and fluids anyway.

    '76 gtb no cats!
  4. SoCal308GTSiQV

    SoCal308GTSiQV Formula Junior

    Nov 3, 2008
    Ojai, Ca.
    Full Name:
    I'll be coming up for another smog in November and I'm a bit nervous. I also live the in "Peoples Republic of California". I have a 1983 308 QV, so I'm Fuel Injected. I passed last time dead on the numbers I was allowed.

    But this past weekend I pulled my exhaust off for donut gaskets only to find out that both Catalytic’s are EMPTY!

    I can only assume that either:
    A) Someone gutted them earlier
    B) They burned out??? (Can this happen?)

    But either way, the car pasted with out Cats!

    I did however, have fresh oil, a new air filter, new plugs, caps and rotors, wires, a lean mixture on the FI, factory timing AND (possibly) most important I ran a can of "GARANTTEED TO PASS" fuel system cleaner.

    Also, I got my smog in Bakersfield on a hot day (90 degrees plus). The car actually heated up towards the end of the test.

    I plan on having the Cats rebuilt for the future. I just don’t want to deal with “THE MAN” on future smog’s!
  5. CliffBeer

    CliffBeer Formula 3

    Apr 3, 2005
    Seattle, Washington
    Full Name:
    There's something wrong with your brother's 911sc. I have a 911sc and actually took the cat off and she passes by a very large margin. Tell him to replace the oxygen sensor - if the O2 sensor is going bad then that will dramatically affect the mixture in a bad way when it comes to passing smog.

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