7.4L, L29 GM Vortec Marine Engine Cylinder Head. This product data sheet is originally written in English. Replaces Mercruiser & Volvo Penta applications years 1991-newer. This is a BRAND NEW. Marine cylinder head for all 7.4L/454 Vortec marine engines. Oval port intake manifold engines. This is an aftermarket replacement cylinder head for Mercruiser, Volvo Penta, OMC, and GM marine 7.4L engines used between the years 1991-newer and comes complete with valves and springs. Complete with valves and springs. Replaces casting #’s: 279, 156. Direct replacement for 7.4L marine engines years 1991-newer. 2.070/1.720 valves. Listing and template services provided by inkFrog. Mercruiser #883492R1 7.4L, L29 GM Vortec Marine Engine Cylinder Head. Complete with valves and springs Direct replacement for 7.4L marine engines years 1991-newer Listing and template services provided by. Marine Engines 4 Less. Track Page Views With.