If you're planning on boring out your 305 engine, you'll want to know what the maximum bore size is. The answer may surprise you - the maximum bore size for a 305 engine is 4.030 inches. This means that you can increase the displacement of your 305 engine by bored it out to 4.030 inches.
Of course, there are other factors to consider when boring out an engine. For example, you'll need to make sure that the new pistons you use are compatible with the new bore size. You'll also need to take care not to damage any of the engine's critical components while boring. But if you're up for the challenge, boring out your 305 engine can be a great way to increase its power and performance.