McLaren 765LT Stage 3 Engine Build: Building the M840T for Serious Power

The McLaren 765LT is already the most aggressive car in McLaren’s longtail lineup. The Spider version adds open-air driving to 755 horsepower from McLaren’s twin-turbocharged 4.0L M840T V8, a 7-speed SSG transmission, and a dry weight that undercuts nearly every competitor in its class. For owners who want to push that platform well beyond factory output, the limiting factor isn’t the chassis or the turbos. It’s the internals. That’s exactly what our Stage 3 engine build program at Motek EuroWerkz in Dallas is designed to solve.

If you’re researching what it takes to build a 765LT, 720S, or any M840T-powered McLaren for big numbers, this is the breakdown of our top-tier Stage 3 program and every option that goes into it.

Why the M840T Needs a Built Engine

The M840T is a 4.0-liter twin-turbocharged flat-plane V8 that McLaren introduced in 2017 across the 720S, Senna, GT, Speedtail, and the 765LT. It’s a significant step up from the 3.8-liter M838T used in earlier cars. The platform found its crowd quickly — on the drag strip it has gone door to door with GT-Rs and R8s while holding its own identity.

But as more owners started modifying their cars, the failures started showing up. Teardowns on high-output builds kept pointing to the same things: excessive oil consumption, early wear, and bent connecting rods. The OEM internals were never built for that kind of load, and McLaren wasn’t offering replacement parts. That gap is exactly what led us to develop our McLaren engine build program.

How Our Engine Program Works

Motek EuroWerkz has been building race engines and high-performance road engines for over 27 years. Every engine that leaves our shop is a complete sealed longblock — no short blocks. You send us your core, we tear it down, recondition everything, and rebuild it to the spec you choose. You get the engine back fully assembled with timing components installed and valve covers and engine covers in place. We also do M838T 3.8L to M840T 4.0L conversions for owners who want to take that step.

The program is tiered. Stage 1 is a complete refresh on our proprietary pistons and connecting rods — a reliable foundation for most high-output street and circuit builds, rated to 1,200 HP. Stage 2 goes further with crankshaft-guided connecting rods, a billet crankshaft, upgraded fasteners, and a complete gasket set, built for serious drag and track cars at 1,500 HP. And then there’s Stage 3.

The Stage 3 Engine Build: Built Around Your Goals

Stage 3 is our top-end program, and it isn’t a fixed parts list. It’s built entirely around your specific goals — your target power level, your fuel type, your turbo setup, and your intended use case. We put the spec together around what you are actually trying to do with the car, whether that’s a no-compromise drag build, a high-horsepower street car, or a dedicated race program. Pricing starts at $80K and scales depending on what goes into the build.

Here are the options that can go into a Stage 3 build:

• Billet Block — A billet-machined engine block for maximum strength and consistency under extreme cylinder pressure, replacing the OEM casting’s limits.
• Dry Sump Conversion — Eliminates oil starvation under sustained high-g cornering and hard launches, critical for track and drag use.
• Syvecs S7+ ECU — A plug-and-play standalone engine management system that unlocks full control over fueling, boost, and timing for big-power tunes.
• M838T to M840T Upgrade — Converting the earlier 3.8L architecture to the 4.0L M840T platform for owners stepping up displacement and capability.
• Custom Crank Profile — A crankshaft ground to a profile that matches your stroke and power targets rather than a one-size-fits-all spec.
• Race Bearings — Race-spec bearings engineered for the loads and RPM of a full-output build.
• Head Porting — Cylinder head porting to improve airflow and support the power the rest of the build is capable of making.

Because every Stage 3 build is configured to the owner’s goals, no two are identical. The right combination of these options depends entirely on what the car is being built to do — and that conversation is where every Stage 3 build starts.

Platforms We Support

Our engine program covers the full McLaren twin-turbo lineup, not just the 765LT:

• M838T (3.8L Twin-Turbo V8): MP4-12C, MP4-12C GT3, 650S, 675LT, MSO 688 HS
• M838TQ (3.8L Hybrid): P1, P1 GTR, P1 LM
• M838TE (3.8L Sport Series): 540C, 570S, 600LT, 620R
• M840T (4.0L Twin-Turbo V8): 720S, 720S GT3, 720S GT3X, 765LT, Speedtail
• M840TR (4.0L Race Spec): Senna, Senna GTR, Elva
• M840TE (4.0L Grand Tourer): GT

Built In-House, Sealed and Ready

Everything that goes into a Stage 3 build — proprietary pistons, connecting rods, crankshafts, cylinder liners, head gaskets, and precision fasteners — is machined to our specs to keep a high-output build together long term. The engine comes back to you as a complete, sealed longblock, ready to drop in.

If you’re planning a build on a 765LT or any McLaren in our supported lineup, the full program breakdown, stage specs, and component part numbers are on our McLaren Engine Builds page.

Talk Through Your Stage 3 Build

Every Stage 3 build starts with a conversation about what you want the car to do. Reach out and we’ll walk through the options and put together a spec around your goals.

Contact Motek EuroWerkz
Phone: (469) 298-2880
Location: 1601 N Central Expy, Plano, TX 75075
Website: motekeuro.com