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By Florida_Phil - 2 Years Ago
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I've been chasing a strange noise in my engine lately. Maybe someone has run into this before? The noise is very intermittent and only happens when I rev the engine slightly. It is a kind of popping sound similar to a cracked exhaust manifold and it seems to be coming from the intake manifold. The engine runs perfectly with no miss or hesitation. I installed metal exhaust manifold gaskets and I have no exhaust leaks. I adjusted and checked the valves and they are perfect. I have a 1957 "B" manifold on my engine with a Holley 465 and an electric choke. I have a PCV. The center exhaust ports that lead to the intake are open. I suspected the noise was coming from the hole in the intake manifold where the original choke was connected. I blocked it off yesterday and it seems to be better. I understand there can be problems with the exhaust crossover in these manifolds? What's the story?
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By 312YBlock - 2 Years Ago
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Probably nothing to do with it but try re-torquing the carb to the intake.
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By Ted - 2 Years Ago
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There is a metal tube going through the heated crossover on the 1957 ECZ-B intake manifolds. That tube is specific for supplying heated air to the automatic choke coil. Air is pulled in on the drivers’ side (left) of the crossover and by way of suction from the carburetor, it is transferred to the passenger side (right) of the crossover and then up to the automatic choke coil. The exhaust going through the crossover simply heats that tube with the air for the choke being isolated from the exhaust.
With time, those tubes within the intake manifold crossover do rust away and can create an exhaust leak at the sides of the manifold. If not using the original automatic choke that requires the heated air from the intake manifold, most people will just tap those holes and install a bolt on each side to eliminate a potential exhaust leak. Those holes will only leak if the tube has been compromised. If retaining the factory automatic chokes, then those tubes are available as replacements at which point the old tube is pressed out and the new one is installed.
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