To tell you the horsepower, I need more information. Please tell me:
* Model Year: What year was the engine manufactured?
* Series: Is it a 453-T, 453-C, 453-E, etc.?
* Configuration: What is the engine's displacement (in cubic inches or liters) and number of cylinders?
Once you provide this information, I can help you find the horsepower rating for your specific Detroit 453 engine.