Carb ran great right out of the box! I put it on my built 440 big block Chrysler. Compared to Edelbrock that I used to break the motor in with, it is a completely different car. I mean bad fast, It gave me goosebumps fast. Yes, I have a lot of other high performance parts on my motor, it's far from stock (550-600 H.P.), this carb really made my car the monster I planned on it being. Great product.