McLaren Cylinder Heads 720s 765LT 4.0 V8

cylinder heads for the McLaren 4.0L V8 (M840T engine) used in the 720S and 765LT are masterpieces of thermal management and high-revving efficiency. While they share the same fundamental architecture, the 765LT versions feature specific internal refinements to handle increased boost and higher thermal loads.

1. Core Engineering: 720S & 765LT

The M840T engine is an “all-aluminum” 90° V8 with a flat-plane crankshaft. The cylinder heads are designed with several key racing-derived features:

• Enhanced Cooling (Water Jackets): Redesigned from the previous 3.8L (M838T) engine, these heads feature optimized internal water channels and jackets to maintain consistent temperatures across the combustion chamber during sustained track use.

• Dual-Fuel Injection: The heads house a sophisticated 16-injector system (two injectors per cylinder). This allows for precise fuel atomization at low loads (efficiency) and massive fuel delivery at high RPM (power).

• Valvetrain: They utilize a dual-overhead-cam (DOHC) layout with four valves per cylinder and finger-follower valve actuation for high-rev stability (redline is typically 

   

2. Technical Specifications

3. The 765LT Distinction

While the 720S and 765LT heads look nearly identical externally, the 765LT heads (and their supporting internal components) include:

• LT-Specific Head Gaskets: Three-layer stainless steel head gaskets designed to withstand the higher peak cylinder pressures of the 765LT’s increased boost.

• Valvetrain Tuning: While the heads themselves are compatible, the 765LT uses a more aggressive ECU map to manage the variable valve timing for a sharper “crescendo” exhaust note.

Installation & Service Notes

• Timing Covers: These are often sold separately or as a set. The part numbers 20000519 (Left) and 20000520 (Right) frequently refer to the complete head assembly including the timing gear covers.

• Compatibility: The 720S cylinder heads are technically a “direct fit” for the M840T engine block, but if you are using them on a 765LT, ensure you use the LT-spec head bolts and gaskets to handle the additional torque.

• Condition Check: If sourcing used heads, it is critical to inspect the cam journals and valve seats. These engines operate at extreme tolerances; even minor scouring on the cam journals can lead to oil pressure issues.