Small Block Chev 327-350-400 186cc Aluminium Cylinder Heads Pair

Aeroflow 186cc Small Block Chevy Cylinder Heads Pair (327-350-400) – Aluminium

Upgrade your small block Chevy with a pair of Aeroflow 186cc aluminium cylinder heads designed for 327, 350, and 400 builds. Built from robust A356-T6 alloy, these heads blend modern casting design with a street-friendly chamber and flow characteristics that wake up idle-to-6500 rpm performance. The result is stronger low- and mid-range torque, snappier throttle response, and a more responsive street/strip package without blowing your budget.

Why these heads stand out

• Ultra-smooth A356-T6 aluminium with 5-angle valve job and hand finishing for improved airflow and combustion efficiency.
• 67cc combustion chamber paired with 186cc intake runners delivers a balanced, performance-oriented compression and breathing path suitable for flat tappet or hydraulic cams.
• 1.43" (stock-like) valve spring capability is surpassed by larger springs to handle higher lift while maintaining valve control, supporting up to performance cam profiles.
• 5-axis improvement touches—diamond-honed bronze valve guides and hand bowl blending—for better longevity and reliability under street/strip use.
• Long-term value: complete heads that come with everything you need for installation and performance—valves, valve springs, retainers & locks, guide plates and 7/16" rocker studs.

Performance profile and ideal applications

Designed for idle to 6500 rpm operation, these 186cc heads are ideal for 4.00" bore engines and larger. They’re suited to both flat tappet and hydraulic camshafts, offering improved flow without sacrificing street manners. The larger intake and tuned exhaust ports contribute to a flatter torque curve, making it easier to drive on the street while still delivering exciting peak power on the strip.

Key specifications at a glance

• Material: A356 Aluminium (T6) with lightweight, strong casting
• Chamber: 67cc
• Intake port volume: 186cc; Intake port dimensions: 2.00" x 1.20"
• Exhaust port volume: 72cc; Exhaust port dimensions: 1.42" H x 1.53" W
• Spark plug location: Straight
• Intake valve diameter: 2.02"
• Exhaust valve diameter: 1.60"
• Valve stem diameter: 11/32"
• Valve spring pocket I.D.: 1.49"
• Valve guide material: Manganese Bronze; Guide O.D.:.530" (0.570" at base)
• Rocker stud thread size: 7/16" x 14
• Valve angle: 23°
• Deck thickness:.625"
• Valve spring details: installed height 1.790", installed pressure 130lbs, open pressure 290lbs @ 500"
• Maximum valve lift:.530" @ 1.260"; coil bind: 1.200"
• Valve spring outside diameter: 1.450"; inside diameter: 0.700"; free length: 1.350"
• Valve spring retainer outside diameter: 1.400"; inside diameter: 0.395"
• Valve spring retainer steps: Step 1 1.060"; Step 2 0.680"
• Valve spring locator outside diameter: 1.570"; inside diameter: 0.565"
• Includes: valves, valve springs, retainers & locks, guide plates, and 7/16" rocker studs
• Bore compatibility: fits 4.00" bore and larger
• Cam compatibility: suits flat tappet and hydraulic cams
• Recommended installation note: IMPORTANT – check installed spring seat pressure and open pressure before installing to ensure correct spring pressure for your application

What’s included

• Pair of complete heads
• Valves, valve springs, retainers & locks
• Guide plates
• 7/16" rocker studs

Installation guidance and considerations

These Aeroflow aluminium heads are designed to offer strong performance with a sensible budget. They are intended for entry-level street performance builds that still demand solid flow characteristics. When installing, verify spring seat pressure and open pressure to match your camshaft profile, especially if upgrading or changing camshafts. Ensure you have compatible 7/16" rocker studs and hardware for a reliable, safe setup. For best results, pairing with appropriate intake and exhaust components and a well-tuned carburetor or EFI calibration will maximize the gains these heads offer.