Small Block Chev 327-350-400 204cc Aluminium Cylinder Heads Pair

Unlock street‑and‑strip performance with Aeroflow’s Small Block Chevy 327-350-400 204cc Aluminium Cylinder Heads (Pair). Built from precision‑cast A356‑T6 aluminium, these heads push flow numbers higher thanks to a fresh runner and chamber design, a 5‑angle competition valve job, and hand‑finished details that help them outperform many brands in the same price bracket. The result is impressive idle to 6500 rpm capability with strong mid‑range power for daily driving and weekend sessions alike.

Key features that set these heads apart

• 204cc intake runners paired with a 67cc combustion chamber for efficient air/fuel mixture and favorable compression characteristics
• Intake port: 2.22" x 1.31" and Exhaust port: 1.34" x 1.39" with straight spark plug location for straightforward installation
• Valve arrangement and sizing: Intake valve 2.02" diameter; Exhaust valve 1.60" diameter; Valve stems 11/32"
• 23° valve angle designed to improve flow and quench characteristics compared to older designs
• Rugged build with Manganese Bronze valve guides and bronze guide honing for durability and reliability
• Deck thickness.625" for a robust foundation and consistent sealing
• Includes everything needed for installation: valves, valve springs, retainers & locks, guide plates, and 7/16" rocker studs
• Designed for entry‑level street performance engines to maximize flow while remaining budget‑friendly

Complete kit highlights

• Valve springs: larger‑than‑stock dual springs with a 1.43" (approx.) outer diameter to handle the rigors of higher lift
• Valve spring specs: installed height 1.790", installed pressure 135 psi; open pressure 290 psi @ 500"; maximum lift 0.540" @ 1.250"; coil bind 1.210"
• Spring dimensions: outside diameter 1.450", inside diameter 0.700", free length 2.350"
• Valve spring retainer outside diameter 1.400"; retainers feature Step 1 1.060" and Step 2 0.680"
• Valve spring locator outside diameter 1.560" and inside diameter 0.560"
• Guide plates and 7/16" rocker studs included for quick, reliable setup
• Spark plug location: Straight for straightforward wiring and plug choice

Technical specifications at a glance

• Material: A356 aluminium
• Chamber: 67cc
• Intake port volume: 204cc
• Intake port dimensions: 2.22" x 1.31"
• Exhaust port volume: 70cc
• Exhaust port dimensions: 1.34" x 1.39"
• Rocker stud thread size: 7/16" x 14
• Valve guide material: Manganese Bronze; guide O.D..530" (0.570" at base)
• Max lift (valve springs): 0.540" at 1.250" installed height
• Deck thickness:.625"
• Intake valve diameter: 2.02"; Exhaust valve diameter: 1.60"
• Valve stem diameter: 11/32"
• Valve spring pocket I.D.: 1.49"
• Valve spring locator I.D.: 0.560"
• Fitment: Suitable for bore sizes 4.00" and larger; supports flat tappet and hydraulic camshafts

Why choose these heads

These Aeroflow aluminium heads are built for drivers who want more flow without sacrificing street manners. The combination of a high‑flow 204cc intake with a compact 67cc chamber delivers improved low‑to‑mid range torque and a potent overall power curve. With premium assembly details and ready‑to‑go components, these heads dramatically reduce setup time and help you realize your engine’s potential on a budget.

Important installation note

Before final assembly, check installed spring seat pressure and open pressure to ensure it matches your camshaft and drivetrain requirements. This step helps guarantee optimal valve train performance and reliability for your specific application.