I have a 1968 Coervette conv. with 4-speed 370 rear end, motor: 427 CAME WITH 3 2BARREL CARBS HOLLEY NOW I HAVE A 850 4BARREL,I RAN THE 1/4 MILE AT GAINESVILLE RACEWAY AT 12.43 @ 111 MILES PER HOUR WITH STREET TIRES, NOT TO BAD. FOR A UNDER CARBURETED 427.