How fast does 638 SAE Certified horsepower get you? When it’s coming from an LS9 in a ZR1, it goes all the way to 205 MPH. I had seen the 205 MPH figure in a Detroit News article this morning, but the video below from GMNext proves what kind of top-end prowess the ZR1 will have. Note also that top speed is in 6th gear, not in 5th as the Z06, showing what kind of grunt the new King of the Hill has.