ATK High Performance 250cc LS1/LS6 Aluminum Cylinder Heads

ATK High Performance 250cc LS1/LS6 aluminum assembled engine cylinder heads are complete new builds. They include valves, valve springs, valve spring retainers, valve stem seals, and soft plugs. All threads are checked and repaired, if necessary; and all passages and part interfaces are pressure checked. Product specifications: * Material: A356 aluminum * Bolt count: 6-bolt head * Intake port volume: 250cc * Intake port dimension: 3.227 in. H x 1.119 in. W * Intake port location: Stock cathedral port * Intake valve size: 2.080 in. * Intake valve material: Stainless steel * Exhaust port volume: 105cc * Exhaust port dimension: 1.628 in. H x 1.722 in. W * Exhaust port location: .086 in. raised * Exhaust valve size: 1.60 in. * Exhaust valve material: Stainless steel * Combustion chamber size: 61cc * Valve cover bolt pattern: Perimeter bolt * Valve angle: 11 degree * Valve spring pocket diameter: 1.610 in. O.D. * Valve spring pac: 1905 dual spring (hydraulic roller) * Valve spring setup height: 1.800 in. * Valve spring closed pressure: 160 lbs. (with retainer) * Valve spring open pressure: 1.200 in., .600 in. lift, 425 lbs. / 1.150 in., .650 in., lift 445 lbs. (with retainer) * Valve spring max lift: .650 in. * Valve guide material: Manganese bronze * Valve seal material: Viton© * Valve seat material: Powder metal * Retainer material: Titanium * Deck thickness: .750 in. * Minimum bore diameter: 3.900 in. (will not fit stock bore 4.8L/5.3L) * Flat mill: .006 in. per cc * Spark plug dimensions: 14mm x .708 in. with tapered seat * Torque specifications per application based on factory or aftermarket bolts/studs Show Less