Comparing bmw engine sizes

Generally with BMW's the numerical model tells you a good bit. The first number is the series (3, 5, 6, 7) the next two are normally the engine displacement. So a 87 325 has a 2.5L I6 motor in it, and a 96 328 has a I6 2.8 (but more electronic limiters).

I don't know the exact sizes off the top of my head but going off the fact that they are both In-line 6, it should fit. You will just need a good bit of parts off of the 325i though.

this is different engine and can be changed but you will have to chage the wiring harnes as well

No, the '87 has the M20 engine, with a rubber timing belt, and much less power. The '96 should have the M52 , with a timing chain, multi-valve head and more power- Go with a used , correct engine for your BMW, it's not worth "reverse engineering" the good old, but mainly "old" M20 engine for your E-36 3 series[E-36 is your body code, BMW gives body codes to each model they build]
Lastly, make sure your overheating problem isn't failed impeller blades on your water pump. The stock pump often uses a plastic impeller blade assembly for pumping the coolant inside your engine, these come loose from the water pump shaft, and you lose actual water/coolant movement. Only cure is a new water pump when this happens. Some people make a metal impeller version of the pump to prevent this nasty/sneaky overheating from happening.

The 325i engine is 2.5 liters, while the 328is engine is 2.8 liters. Additionally, the '87 is an e30 generation car while the '96 is an e36. I am not sure that engines between generations are interchangable, at least not without some fabrication. Check with RoadFly.com under the BMW e36 section and post the question. If no one here can tell you definitively, RoadFly guys will.

The electronics for the two engines are completely different. Theoretically you can put any engine in any car, however practically I would not. The 325 has a 2.5l engine the 328 has a 2.8l engine. Different engines, different electronics, different transmissions. Wouldn't recommend trying to swap the engines. Your best bet would be to resolve the over heating issue which could be due to a defective thermostat or even a broken water pump.

Hello There

The engine in an E30 325i is not the same as the E36 328i. the 325 has a 2.5 litre engine and the 328is has a 2.8 litre engine. They are from a diffrent era. The engine in the 328i Has the engine code M52 and conpletely redesigned.

Hope this helps. Pleas don't forget to rate me.