PRC LS3 As-Cast 257cc Rectangle-Port Cylinder Heads — 68cc Chamber

PRC LS3 As-Cast 257cc Rectangle-Port Cylinder Heads — 68cc Chamber

Part Number: PRC-SSLS3AC

Precision Race Components PRC-SSLS3AC cylinder heads are high-flow as-cast LS3-style rectangle-port heads designed for LS3, L99, L92, LSA, and LS9 applications. The heads combine 257cc as-cast intake runners with CNC-machined 68cc combustion chambers and valve-guide machining, providing a strong airflow increase without requiring a fully CNC-ported intake runner.

PRC flow-bench testing reports up to 369 CFM of intake airflow at 0.650-inch valve lift. The casting uses a thicker deck surface intended for power-adder applications, relocated valves with a 13-degree valve angle, 2.170-inch hollow-stem stainless-steel intake valves, and 1.600-inch stainless-steel exhaust valves. The assembled set is supplied with TSP .660-inch dual valve springs using PAC springs and titanium retainers.

Key Features

• 257cc as-cast LS3-style rectangle-port intake runners
• 68cc CNC-machined combustion chambers
• CNC-machined valve-guide areas
• PRC flow-bench tested intake airflow up to 369 CFM
• Thicker deck surface for improved cylinder-head clamping strength in high-load applications
• Relocated valves with 13-degree valve angles
• 2.170-inch hollow-stem stainless-steel intake valves
• 1.600-inch stainless-steel exhaust valves
• TSP .660-inch dual valve-spring package with PAC springs
• Titanium valve-spring retainers
• Uses factory LS3-style rocker arms
• Cast and machined in the USA

Kit Includes

• Pair of fully assembled PRC LS3 as-cast cylinder heads
• 2.170-inch hollow-stem stainless-steel intake valves
• 1.600-inch stainless-steel exhaust valves
• TSP .660-inch dual valve springs with PAC springs
• Titanium retainers

Technical Specifications

• Intake port configuration: LS3-style rectangle port
• Intake runner volume: 257cc
• Combustion chamber volume: 68cc
• Combustion chamber finish: CNC machined
• Valve angle: 13 degrees
• Intake valve diameter: 2.170 in
• Intake valve construction: Hollow-stem stainless steel
• Exhaust valve diameter: 1.600 in
• Exhaust valve material: Stainless steel
• Valve-spring configuration: TSP .660-inch dual spring kit with PAC springs
• Retainers: Titanium
• Rocker-arm compatibility: Factory LS3-style rocker arms
• Published peak intake flow: 369 CFM @ .650-inch lift
• Published peak exhaust flow: 233 CFM @ .650-inch lift

Published Flow Data

Application Notes

• PRC/Texas Speed lists these heads for LS3, L99, L92, LSA, and LS9 applications using the LS3-style rectangle-port intake architecture.
• The LS3-style rectangle-port configuration requires a compatible LS3/L92-style intake manifold and corresponding intake-port components.
• The 68cc chamber is the standard configuration for PRC-SSLS3AC. Final compression ratio depends on displacement, piston configuration, deck height, head-gasket dimensions, and actual chamber volume.
• The thicker deck surface is intended to improve head retention and sealing margin in boosted, supercharged, nitrous, and other high-cylinder-pressure combinations.
• Pushrod length, piston-to-valve clearance, and complete valvetrain geometry should be verified for the specific engine and camshaft combination.
• Head gaskets, head bolts or studs, rocker arms, pushrods, intake manifold, exhaust components, and installation gaskets/hardware are not listed as included with this cylinder-head set.

Emissions and Competition-Use Notice

This product is not legal for sale or use in the state of California. Installation or use on an emissions-controlled vehicle may also be restricted by federal, state, or local law. The purchaser and installer are responsible for confirming that the completed vehicle and application comply with all applicable emissions and vehicle-use requirements.