1. What Is a Top Swap?
A “top swap” involves removing the naturally aspirated components (intake manifold, throttle body, etc.) from an L36 or L26 3800 engine and replacing them with the supercharged parts (intake manifold, supercharger, throttle body, injectors, etc.) usually found on the L67 or L32 3800 engines. The goal is to gain forced induction while keeping the original engine block in the vehicle.
Important Note: The bottom end (rods, pistons) in the NA engine is not as robust as the L67/L32. If you plan to push high boost levels, internal upgrades or a complete L67/L32 swap may be a safer route.
2. Parts and Components Required
Here’s a typical list of parts you’ll need for a successful top swap. Some of these can be sourced from a donor L67/L32 engine or purchased new/remanufactured.
– Supercharger Assembly (Eaton M90 Gen 3 or Gen 5)
– Supercharged Lower Intake Manifold (L67 or L32)
– Supercharged Cylinder Heads (L67/L32)
– Harmonic Balancer/Pulley
– Idler/Tensioner Pulleys & Brackets
– Fuel Injectors (Higher flow; typically 33 lb/hr or more)
– Fuel Rail (shaped differently for SC)
– Throttle Body (SC TB recommended)
– MAP Sensor (2-bar or 3-bar)
– Head Bolts (New, torque-to-yield)
– Spark Plugs (colder heat range recommended)
– Belt(s) (SC belt and accessory belt)
– Engine harness if going L26 to L32 due to the dual map sensor setup to avoid EGR and SES issues
Note: This only applies to the 2004+ Grand Prix with the L26
Optional / Recommended:
– PCM Tuning (required) We do offer a base tune. Reach out via the forums for pricing.
– Upgraded Exhaust
– Cooler Thermostat (180°F)
– Knock Sensors / Wiring
3. Preparation
– Gather All Parts
– Label or Organize components
– Drain Fluids
– Disconnect Battery
4. Removal Steps (NA Components)
– Remove Engine Cover & Accessories
– Fuel System: Relieve pressure and disconnect lines
– Exhaust (if needed for clearance)
– Intake & Heads
– Clean and Inspect all surfaces and parts
5. Installation Steps (SC Components)
– Install Supercharged Cylinder Heads
– Supercharged Lower Intake Manifold
– Supercharger Assembly & Throttle Body
– Fuel Rail & Injectors
– Front Drive & Harmonic Balancer
– Belts & Pulleys
– Sensors & Wiring
– Exhaust System
– Coolant & Oil
6. First Start & Break-In
Double-check all connections, prime the fuel system, and monitor for leaks or issues during the first start. Adjust tuning as needed.
7. Tips and Considerations
– Knock/Detonation management
– Pulley Size caution
– Supporting Mods for reliability
– Transmission impact with increased torque
8. Conclusion
The top swap is an excellent way to gain supercharged power without a full engine replacement. It requires careful planning, mechanical skill, and a proper tune to ensure reliability. Always refer to a factory service manual and perform modifications at your own risk.
Need Help? Join the Discussion!
If you need additional help, have questions, or want to share your progress, join the community discussions on our forums. Connect with other enthusiasts who have completed the 3800 top swap and learn from their experiences.
Visit the forums at: WBodyTech Forums
Are you having issues? Check out the Official Support Thread – 3800 NA to Supercharged Top Swap Guide
