Cylinder Head¶
Where the engine breathes. Port flow and valve size set how much air gets in, which is the biggest single influence on VE.
What it is¶
The cylinder head carries the valves and ports through which the engine breathes. Its tuning properties: port flow coefficients, valve sizes and valves per cylinder, combustion efficiency, and a head type spanning from mild commuter castings to full race heads. Better heads flow more air and burn more completely.
Why it matters¶
- Breathing → VE — port flow and valve area are dominant inputs to volumetric efficiency. A head that flows well lifts the whole VE curve, especially up top.
- Combustion efficiency — a better chamber burns more completely, and a good head tolerates more advance and a leaner mixture before knock — it effectively raises the knock limit.
How to tune it¶
The head is one of the most effective power upgrades because it raises VE directly. Match it to the rest of the build: a race head's high-RPM flow only pays off with a cam, intake, and exhaust that can use it, and injectors sized for the extra air.
Rule of thumb
A better head raises VE and buys timing/lean tolerance — but it shifts the engine's character upward. Pair it with breathing hardware tuned for the same RPM band.
In the game¶
Head selection on the Setup page changes the derived VE curve and the knock/advance behavior. Confirm fuelling keeps up after a head upgrade — more air needs more fuel.