The roll pin in the distributor drive gear may be broken. Remove distributor and check.
Camshaft broken, But not very common in stock engines.
Timing chain broken. Not common either. Cam gear on the timing gear may be striped off/teeth gone. Check timing chain.
The engine turns the rotor through a transmission.
The engine is driving a transmission which turns the rotor
1 - 5 - 3 - 6 - 2 - 4 The distributor rotor turns CLOCKWISE
1-2-3-4-5-6 Rotor turns clockwise1-2-3-4-5-6 Rotor turns clockwise
All Chevy V8 engines in 1968 1-8-4-3-6-5-7-2 rotor turns clockwise.
Rotor turns clockwise.
For a Mercury / Ford 3.0 liter V6 engine : ( the distributor rotor turns CLOCKWISE )
The 406 is a Ford engine with firing order 1-5-4-2-6-3-7-8 Rotor turns counterclockwise. Chevrolet never made a 406.
The small block chevy turns in a clockwise rotation.
Ford V8 engine - COUNTERCLOCKWISE Ford straight 6 cylinder engine - CLOCKWISE
the turtle wins the race
The firing order of the Chevy 366 big block truck engine is 1-8-4-3-6-5-7-2 Rotor turns clockwise. Click the link and you will see a diagram of a 1982 Chevy 350 V8 which is exactly the same as the 366.