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Vaccum Low After Heads Swap

This is a discussion on Vaccum Low After Heads Swap within the General Help forums, part of the LSx Technical Help Section category; Hi guys, I just finished installing my new heads 7 days ago and when it was all said and done ...

  1. #1
    Junior Member
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    Jul 2006
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    tx
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    Black
    2001 Trans Am

    Unhappy Vaccum Low After Heads Swap

    Hi guys, I just finished installing my new heads 7 days ago and when it was all said and done the car has very low vaccum.

    My gauge before that usually showed between 17-21 hg and now it only shows 9-11 hg. I tried torquing the manifold bolts down, and made sure all vaccum lines were connected.

    I sprayed starting fluid all around the manifold, throttle body and pcv areas and I hear no difference in the way the motor revs. Is it possible that the intake didnt seat properly?

    I had the headers welded to the y pipe. When I punch it, it backfires and may sound like the welder may have missed a spot.

    I didnt swap in a new cam, its still stock and I am now running 7.350 pushrods because the heads were milled.030 , the valves were bigger on the new heads and also have dual springs.Any ideas as to why my vaccum is lower?

    What else could cause the vaccum to be low? The car drives fine and idles okay, but every now and then it pings or surges. Any help is welcome

  2. #2
    Senior Member mrr23's Avatar
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    Jul 2005
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    dark bowling green
    2000 corvette

    the only thing it can be is the intake didn't seal. even though you sprayed around the top of the intake, it could be leaking from the bottom side. did you use new rubber seals?

  3. #3
    Junior Member
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    tx
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    2001 Trans Am

    mrr23,

    Thanks for your reply. No, didnt change the intake gasket seals. But I will do that. Thanks

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