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A forum for the owners and enthusiasts of General Motors B-Bodies from 1977-1990, but dedicated to the owners of 1977-1979 Impalas and Caprices. Join up now!


4 posters

    venting gas tank vapors

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    paulboncz
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    Post  paulboncz Sun Nov 15, 2015 2:53 pm

    My 1979 Impala has a new stock 350 SB crate engine (no performance add-ons, no headers, no emissions control). The new intake manifold and 600 cfm carb  are Edelbrock. The tranny is automatic. I wish to vent the gas tank vapors to the correct place. I don't want to affect engine performance nor do I want to smell gas after the car is parked in the garage. So, what connections should I make in the engine bay to the hose which runs from the gas tank. Right now it's connected to a charcoal canister filter. If that's ok, where should I vent vapors from the canister? That's my question. For those of you who have an engine set up similar to mine, what do you do with your vapors. Maybe the answer is obvious. If so, I'm sorry but I'm not sure what it is. In my State, I'm exempt from emissions testing. Thanks for reading my post.
    oldsbuickhybrid
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    Post  oldsbuickhybrid Mon Nov 16, 2015 2:46 am

    lol I had just posted a thread similar to this in another forum Very Happy I am not as lucky as you though, and my charcoal canister is gone. Anyways, since you do have the charcoal canister, a hose runs from the fuel sender in the gas tank, to the canister, and from the canister, it goes to the carb.
    Sweet Seventy9
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    Post  Sweet Seventy9 Mon Nov 16, 2015 10:11 am

    What he said ↑↑
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    paulboncz
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    Post  paulboncz Mon Nov 16, 2015 10:26 am

    So, I'm going to send the vapors from the charcoal canister to the unused non-ported vac inlet on my 600 cfm Edelbrock carb and not worry about any effect on engine starting or performance? Thanks to both of you for the replies.







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    Myloth
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    Post  Myloth Mon Nov 16, 2015 10:37 am

    That doesn't sound right to me it should go to the ported vacuum on some it is bowl vent

    but on the edelbrock just hook it to the left side of the front of the carb. Your distributor goes

    to the right the manifold vacuum. Ported vacuum for distributors was a cheap emissions trick

    of Car companies in the 70s before computers it lowers emissions at idle but does nothing

    for mpg or hp.
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    Post  paulboncz Mon Nov 16, 2015 1:18 pm

    Thank you Myloth. I will try your suggestion. The reason the distrib vac, at this time, is taken from the ported side of the carb is because an Edelbrock YouTube video directed me to do so. No matter. One last dumb question on this subject. Does moving the distrib vac from ported to non-ported affect the timing? I'm guessing no.
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    Post  Myloth Mon Nov 16, 2015 4:23 pm

    Yes it does at idle it increases the timing as long as you are at or near factory specs on timing

     it smooths the idle out, it may increase your idle speed just lower it and you should get better

    mpg and throttle response. And as I said before the only benefit to having it the other way

    around is lower emissions at idle nothing else.

    Many think it's proper to use the ported for the distributor advance but that

    is because the cars came that way from the factory and it was all just an emissions thing.

    There are several good articles about this one was in Hot Rod I think it's online.

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