HPLS1250 Aluminum Cylinder Head for GM Gen III/IV LS Engines, LS1/LS6 Cathedral Ports

Name: HPLS1250 Aluminum Cylinder Head for GM Gen III/IV LS Engines, LS1/LS6 Cathedral Ports
Brand: ATK ENGINES
SKU: 059-HPLS1250
Price: 1029.00 USD
Availability: InStock

^$1,029⁰⁰

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GM Gen III/IV LS

Aluminum Cylinder Head

GM Gen III/IV LS Engines

LS1/LS6-Style Cathedral Ports

Combustion Chamber: 61 cc

Intake Valve: 2.08 in.

Exhaust Valve: 1.60 in.

Intake Port: Stock 250 cc

Exhaust Port: Raised .086 in.

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ATK Engines HPLS1250 Aluminum Cylinder Head Specs:

Material: A356 Aluminum
Bolt Count: 6-Bolt Head
Intake Port Volume: 250 cc
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: 105 cc
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: 61 cc
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 (Hyd. Roller)
Valve Spring Setup Height: 1.800 in.
Valve Spring Closed Pressure: 160 lbs. (w/Retainer)
Valve Spring Open Pressure: 1.200 in. .600 in. Lift 425lbs / 1.150 in. .650 in. Lift 445 lbs. (w/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: Based on Factory or Aftermarket Bolts/Studs

ATK Engines HPLS1250 Recommended Components:

Intake Port Gasket: Factory GM
Exhaust Port Gasket: Factory GM
Head Gasket Factory Block: 3.900 in. GM 12589226 or 4 in. GM 12610046 (each sold separately)
Head Gasket Aftermarket Block: 4.125 in. Cometic MLX
Spark Plug Starting Range: NGK TR55 or equivalent (sold separately)
Lifters: .600 in. per applications (lifters w/aftermarket tie bar recommended)
Pushrods: 3/8 in. Pushrods are recommended (must check length)
Rocker Arms: OEM w/upgraded Trunnions or aftermarket

ATK Engines HPLS1250 Flow Data:

Flow Tested on a Super Flow SF600 bench with a 4.030 in. bore size @28 in. water. Clay intake radius was used, Flow tube was not used on the exhaust port.,

Please CLICK HERE for ATK Warranty

Upgrade Your Cylinder Heads

ATK High-Performance Cylinder Heads save time and trouble sourcing cores and or waiting for machine shops. ATK has multiple head combinations. The valve springs provided are an upgrade to OEM and allow for the use of a Hydraulic Roller or Hydraulic Flat Tappet camshaft.

Part TypeCylinder Head

Product LineATK High-Performance Cylinder Heads

BrandATK ENGINES

Package Height9.0

Package Width9.8

Package Length24.3

Weight35.44 PG

Part CategoryPerformance Parts

Valve Springs IncludedYes

Cylinder Head MaterialAluminum

Rocker Arms IncludedNo

Intake Port Volume (Cc)250