* Engine Mounts: The 2.4L Ecotec will likely require different engine mounts. The mounting points on the chassis might not perfectly align, requiring custom fabrication or significant modification.
* Transmission Compatibility: The transmission from the 2.2L might not be compatible with the 2.4L Ecotec. You might need a transmission from a car that originally came with the 2.4L, which adds to the complexity and cost. Even if the bolt pattern matches, internal components might not handle the potentially higher torque of the 2.4L.
* Wiring Harness and Computer (ECU): The 2.2L's wiring harness and Engine Control Unit (ECU) are not compatible with the 2.4L Ecotec. You'll need the entire harness and ECU from a donor car with the 2.4L, and even then, significant wiring modifications are likely required to integrate it into the Cavalier's existing system.
* Exhaust System: The exhaust manifold and piping will almost certainly need to be replaced or significantly modified to fit the 2.4L Ecotec.
* Other Components: Consider the compatibility of other components like the cooling system (radiator, hoses, thermostat), intake manifold, and accessories (alternator, power steering pump). These might need to be swapped as well.
In short: It's feasible but incredibly difficult and expensive. Unless you're a very experienced mechanic with access to parts and tools, it's strongly advised against. The cost of parts, labor, and potential unforeseen issues could easily exceed the value of the vehicle. You're likely better off finding a Cavalier that already has the 2.4L Ecotec or focusing on repairs or a replacement for the existing 2.2L engine.
