• 255cc Intake, 95cc Exhaust & 69cc Chambers
• Virgin A356 Aluminum Castings
• 6 Bolt Head Casting with Extra Strength Decks
• Advanced 11° Valve Angle for Maximum Flow & PTV Clearance
• 2.165” Intake Valve 21-4N Alloy & 1.60” Exhaust Valve 23-8N Super Alloy
• 0.210" Intake Free Drop & 0.250" Exhaust Free Drop
• 23-8N Alloy has the same high temp characteristics of “Inconel” w/o the brittleness
• Available Complete w/ Chromoly Retainers, Ti Retainers, or Bare w/ Valves
• Billet Rocker Arm Stands Included - Compatible w/ OEM LS3 Rocker Arms
• Compatible w/ 4 Bolt OEM Engine Blocks - 4.000" Minimum Bore Required
• Price is for a Complete Set

0.660" Spring Specs:

• 145# @ 1.800"
• 400# @ 1.130"
• CB @ 1.070"

0.700" Spring Specs:

• 170# @ 1.800"
• 450# @ 1.115"
• CB @ 1.000"

Head Flow Data @ 28inHg, 4.125" Bore, Intake w/ Radius, Exhaust w/o Pipe

It MUST be noted that comparing flow data across different flow benches and cylinder heads is NOT the correct way to measure a cylinder head's performance. A flow bench measures static air flow while the engine's valve is at a stationary position. In the real world, the valve nor the air in the cylinder head's runner is ever stationary. The air/fuel mixture is constantly being pushed, pulled & pulsed by the pistons & other cylinder's valve events. A well performing cylinder head must be able to respond to the valve opening and efficiently deliver the air/fuel mixture that the engine is requiring, while also keeping turbulence to a minimum. This is where the Smeding 11° design is unbeatable. On the dyno these heads will out perform other manufacture's 12° designs, even though they advertise higher flow numbers. Below is a dyno comparison of our 11° 260cc CNC cylinder heads vs a competitors 12° CNC 260cc cylinder heads. The test engine was a mild 11.0:1 441" LS engine with our 245/256 Rectangle Port R4 Stroker camshaft. Both dyno pulls were done the same day, with both tunes optimized for each combination. As you can see the 11° Smeding heads outperformed the 12° competitor's heads across the entire curve.