Whats this mean? Taken from a cosworth workshop manual..


The oil gallery of the cylinder head is fitted with a non-return valve which eliminates oil drain back after the engine is switched off
When starting the engine the anti-drain back valve opens for immediate lubrication of the camshaft journals and hydraulic tappets.

Anti-drain back valve in cylinder head
1 = Ball in closed position (engine switched off)
2 = Cross drilling
3 = Cylinder head bolt drilling (oil gallery)
4 = Main oil gallery

Anti-drain back valve in cylinder head
1 = Ball in open position (with engine in operation)
2 = Direction of oil flow

The cylinder head gasket differs from the standard OHC gasket in that it has revised openings to match the Cosworth cylinder head.