[sycraft]

Engine Component Description (LFX)
The High Feature V6 (VIN Code Identifier “3” for both cars and trucks) RPO LFX is a 3.6 Liter VVT (Variable Valve Timing) engine with direct injection. The LFX has E85-compatible valves and seats with special materials and coatings that require slightly different service procedures from gasoline valves. The direct injection system places the high pressure injectors in the cylinder heads. This engine incorporates 2 intake and 2 exhaust valves per cylinder, and uses a dual overhead cam design with individual intake and exhaust camshafts. A camshaft position actuator is mounted on each camshaft. The cylinders are arranged in 2 banks of 3 with a 60 degree included angle. The right bank of cylinders are number 1-3-5 and the left bank of cylinders are 2-4-6, viewed from the flywheel end of the engine. The engine firing order is 1-2-3-4-5-6.

as per GM technical Info