This valvetrain architecture places the intake and exhaust valves parallel to the cylinder bore, opening upward into a combustion chamber cast into a simple cylinder head. The design eliminates the need for pushrods or overhead camshafts, making the engine incredibly simple and compact. However, the tortuous path the airflow must take severely limits volumetric efficiency and compression ratios, leading to its replacement by overhead valve designs.
We're rebuilding a flathead Ford V8, so we've to lap every side valve directly in the block.
Also heard as
- flathead
- L-head
Do not mix it up with
- Overhead valve: A side valve engine has valves in the block, whereas an overhead valve engine places them in the cylinder head above the piston.
Related terms
Overhead valve
An engine design where the intake and exhaust valves sit in the cylinder head above the combustion chamber.
Overhead cam
A valvetrain layout where the camshaft is located in the cylinder head above the combustion chamber.
Cylinder head
This cast metal component bolts to the top of the engine block to seal the combustion chambers.