* Size and shape of the ports: Intake ports are generally larger and more rounded than exhaust ports. Exhaust ports are often smaller and more oval or irregularly shaped to facilitate better flow. This difference is subtle but usually noticeable upon close inspection.
* Runner Length: Intake runners are typically longer than exhaust runners.
* Casting markings: The manifolds themselves might have casting numbers or markings that could indicate intake or exhaust. However, this is not a reliable method as these markings are not always consistent or easily visible. You might need to refer to a parts diagram or service manual specific to your engine's year and model.
* Location of the EGR valve (if present): The exhaust gas recirculation (EGR) valve, if equipped, will always be connected to the exhaust manifold. Identifying the EGR valve's connection point helps pinpoint the exhaust manifold.
* Thickness of the manifold: The exhaust manifold is generally thicker and heavier-duty than the intake manifold, designed to withstand higher temperatures and pressure.
* Sensor placement: Various sensors like oxygen sensors (O2 sensors) will be present on the exhaust manifold, but not on the intake manifold.
The best way: If you have any doubt, refer to a repair manual or parts diagram specific to your engine's year and model. These resources will clearly show the intake and exhaust manifolds with their respective locations and connections. Online resources like websites specializing in GM parts or repair manuals may also be helpful.
