Designed for Gen IV LS engines equipped with LS3, L92 and L76 cylinder heads, this manifold is for EFI or carbureted racing applications operating between 3500-7500 rpm. This manifold uses a standard square-bore carb flange that is compatible with both Edelbrock EFI intake elbows and single bore 90mm throttle body or four-barrel #4150 throttle bodies. EFI manifold #28455 has additional bosses and machining that allow for the use of fuel injectors when combined with the #3638 fuel rail kit (sold separately. The LS3, L92 and L76 all use the same cylinder head. L92 heads are only compatible with a 4.00" and larger bore diameters; smaller bores (including most 5.7L blocks) will require valve reliefs cut into the block. Throttle Body Recommendations: Edelbrock #38783. Installation Notes: Uses LS3/L76/L92 style individual port O-ring seals GM PN19256623, L92 heads are intended for 4.00" bores and will not work with 5.7L blocks without valve reliefs. Manifold Dimensions: R-1.85", F-0.57", H-2.42", CH-7.40", CA-0°. Carb height (CH) for this manifold is measured from the valley cover flange to the carb pad.