WARNING: Cancer and Reproductive Harm – 
The XSFLOW 365cc Big Block CNC-Ported Heads are engineered for maximum airflow, efficiency, and power in high-performance Chevrolet big block applications. Designed using advanced computational fluid dynamics (CFD) modeling and precision CNC machining, these heads deliver superior flow characteristics, combustion efficiency, and horsepower potential across a wide RPM range. Each head is cast from high-density 356-T6 aluminum and heat-treated for durability and stability under high-load conditions. The port and chamber design is optimized for consistent cross-sectional area and surface finish, ensuring balanced cylinder-to-cylinder performance. Ideal for naturally aspirated, nitrous, and boosted big block builds. Recommended for race, marine, and high-performance street engines.
Technical Specifications:
- Engine Compatibility: Chevrolet Big Block (Mark IV, Gen V/VI
- Finish: Natural / Machined
- Valve Seat Machine Style: 5-Angle
- Intake Valve Diameter: 250”
- Exhaust Valve Diameter: 880”
- Valve Length: Intake = +.100″ Longer / Exhaust = Stock Length
- Valve Stem Diameter: .3415″ – 11/32″
- Intake Runner Volume: 365cc
- Exhaust Port Volume: 156cc
- Combustion Chamber Volume: 135cc
- Intake Port Dims: 510” x 1.820” x 3/8” Radius
- Exhaust Port Dims: 690” x 1.900”
- Intake Port Location: Stock
- Exhaust Port Location: .357” Raised
- Deck Thickness: .450”
- Accessory Bolt Holes: Yes
- Intake Valve Angle: 24 deg. / 4 deg.
- Exhaust Valve Angle: 15 deg. / 4 deg.
- Valve Seat Material: Hardened Ductile Iron
- Valve Spring Pocket Diameter: 750” OD (Max Machining)
- Valve Guide Material: Intake = Manganese Bronze & Exhaust = Phosphor Bronze
- Valve Guide Size: 1/2”
- Valve Guide clearance: .0014″ – .002″ (with .3415 Dia valve stem)
- Spark Plug Dimensions: 14mm x .750” with Gasket Seat
- Block Use Type: Iron or Aluminum
Key Features:
- Precision CNC-ported intake and exhaust runners for maximum airflow efficiency
- Raised runner design for improved volumetric efficiency and high-RPM power
- Reinforced rocker stud bosses and thicker decks for high-compression or boosted applications
- Compatible with standard BBC valve train geometry and intake manifolds
SKU# XSF-4365CM
