How much does brand new rebuilt motor add to value af a 1995 z28.

Unless it's a special motor, you have only "maintained" the car. It will definitely be a big selling point if you want to sell it or a good point if you are buying it. You know the motor should be good for many years. Did the motor have high mileage and that's why it was rebuilt? Was the motor raced and abused and that's why it was rebuilt? Has the rest of the car been totally restored to new? These are all thing to consider. You can look on various sites to determine the car's value. Honestly, a rebuild motor, in my opinion, does not increase the value, but just makes it more desirable. It's kind of like having a very low mileage car.