25534371 Vortec Bow-Tie Large Port Cylinder Head, Bare
GM Performance Parts' latest and most powerful iron cylinder head with "large ports" for Street or Racing. This Vortec design Special Performance cast iron cylinder head features revised intake and exhaust ports and machined for 2.00" intake valve and 1.55" exhaust valves. The deck surface is .450" with 65 cc combustion chambers, 206 cc intake and 77 c exhaust ports.
All Vortec intake ports are taller and narrower than early model Chevrolet heads. The valve cover mounting holes are for both early model flange and late model center. This head also includes intake manifold mounting holes for both early model 6 bolt main and late model 4 bolt Vortec design. The head is machined for 3/8" screw in rocker studs, large valve spring pocket machining and will accept up to .530" lift camshafts without modifications. Heads are identified with the Bow-Tie logo on the exterior of the head below exhaust flange and Vortec logo on top of intake port area. They also feature GM logo cast into bottom of intake ports.
Technical Notes: You must use a raised runner design intake mainifold P/N 10051103 (6 bolt mounting), or Vortec design 12366573, 12496820, 12496821, 12496822, and 12499371 (4 bolt mounting) with this head. You can use production Vortec intake gaskets P/N 12529094 (torque spec. 11 ft-lb/ 15Nm) for mounting Vortec design heads or use P/N 12497760 (torque spec. 30 ft-lb) with conventional material when using on early model raised runner or Vortec design intake manifolds, this gasket has both 6 bolt and 4 bolt Vortec attaching holes. Head casting P/N 25534371C. Straight spark plugs.