What is the least you can bore over on a 350 engine?

The least you can bore a 350 small-block Chevy engine is generally considered to be 0.010 inches (0.25mm). However, going this small amount might not significantly increase displacement or power, and may not be worth the cost and effort. Some machinists may be unwilling to bore so little due to the difficulty of achieving precision at such a small increment. Going to 0.020 inches (0.51mm) is more typical for a first overbore.