Can you put a 1.6 geo engine into a car that had a 1.8?

Yes, you can generally install a 1.6-liter geo engine into a car that originally had a 1.8-liter engine, but there are several factors to consider. You may need to modify the engine mounts, wiring harness, and possibly the transmission to ensure compatibility. Additionally, performance and power output will differ, so the vehicle's overall dynamics may change. It's advisable to consult with a professional mechanic for a successful swap.