Too know were 1 and 8 is on a 2000 grand marquis 406 engine?

On a 2000 Ford Grand Marquis with a 4.6L (281 cubic inch) V8 engine (often referred to as a 4.6L Modular engine, *not* a 406), cylinders 1 and 8 are located on the *passenger side* of the engine. They are at opposite ends of the "V" configuration.

* Cylinder 1: Is typically at the *front* of the engine (closest to the radiator) on the passenger side.

* Cylinder 8: Is at the *rear* of the engine (closest to the firewall) on the passenger side.

To be absolutely certain, consult a repair manual specific to your year and engine. These manuals will have detailed diagrams showing the cylinder number arrangement. You can find these manuals online or at auto parts stores. The diagrams will often include markings on the valve covers or intake manifold to help you identify the cylinders.