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Why Would Exhaust Manifold Gasket Blow
  • awca12a
    Posts: 42Senior Contributor
    My '29 Essex kept stalling every time I took my foot off the gas and I

    had to resort to rolling starts to make it home because the battery was

    finally exhausted from all the restarts. Once in the garage, I found

    black smoke puffing from under the exhaust manifold next to both of the

    long exhaust manifold studs. (Part #BM 63553) I'm probably getting the

    wording wrong but I believe it is directly under the carb riser to

    exhaust manifold and bounded by the long studs.



    My question is before I simply take off the carb and exhaust manifold

    to replace the gasket, what would cause exhaust to blow-by this area at

    idle (and running) when it was working like a top all morning?



    I'm still new to motor teardown so perhaps I'm missing somthing basic

    like ????



    THanks



    David Weinstein

    '29 Essex Roadster

    '72 Corvette Cvt
  • Dave53-7C
    Posts: 2,523Platinum Member
    As far as exhaust maifold gasket failure goes, age and improper installation are causes, but heat is the true enemy.
  • Harry HillHarry Hill
    Posts: 1,303Platinum Member
    It sounds like you have an obstructed exhaust system. Has the car been sitting, possible rat nest. Also, check to see if your the flapper in the manifold is stuck closed.



    Harry
  • Steve E.
    Posts: 520Platinum Member
    Also check to see if the gasket surface of the manifold is true and flat.
  • Harry HillHarry Hill
    Posts: 1,303Platinum Member
    Dave, does it seem like it doesn't have any power? I'm wondering if it was running fine before this started happening or was this the first time you had it out. Does this car have a heat exchange butterfly flap to push hot exhaust gasses up to the intake until the car is warmed up. Maybe the it's stuck closed and is causing the manifold to get too hot. It could also cause the gas to boil in the carb and vapor lock.



    Harry
  • ESSX28-1ESSX28-1
    Posts: 995Platinum Member
    Check your that both your vacuum tank & your carb float are working as they should.
    Dave Y
    New Zealand
  • Posts: 0
    Did it ever back-fire? If so, that would be an above-average amount of exhaust pressure, perhaps above the design pressure of the gasket, and potentially leading to the premature failure. When you replace it be sure to torque to specs and recheck the torque twice a year.