Swap Guide

Putting a GM V8 into a BMW E9x 3-series or E8x 1-series gets you a stiff, well-balanced chassis with cheap, proven V8 power. We've been building this swap since 2016. Every part starts in CAD and gets tested on our own cars before it ships, and there are hundreds of completed swaps on the road running this hardware.

This page is the outline: what happens at each stage and where the detailed write-up lives. The complete parts list is the companion to this page and covers every part, system by system.

Step 1: Know your chassis

Every E9x and E8x shares the same front subframe, so the same mounts and crossmembers bolt into all of them: E90 sedan, E91 wagon, E92 coupe, E93 convertible, E82 coupe, E88 convertible, and the early X1. The body styles guide covers all eight body styles and what each one means for the swap. Three special cases:

M3 cars use their own front subframe, so they take the M3 version of our mounts and need a standard rotation power steering pump.
xDrive cars have two routes: keep the xDrive subframe and remove the front diff and axles, or convert to a RWD front subframe, which frees up exhaust clearance and steers better, for a few hundred dollars of junkyard parts. Either way the tunnel is still xDrive shaped, so you'll run the xDrive transmission crossmember, and there's no keeping AWD. Fitment photos are in the xDrive subframe post.
N55 cars keep their DME under the intake manifold instead of in the DME box, which moves a few wiring points. The N55 notes cover it.

Step 2: Pick your engine

Any LS bolts to the same mounting points, from a junkyard 5.3 truck motor to an LS7. The only one to skip is the front-wheel-drive LS4. Iron block truck engines are still the budget boost play: stock bottom end 5.3s and 6.0s have made 700 hp and more with a turbo, a cam, and supporting fuel system work.

Building naturally aspirated? Look at a Gen V LT before you commit. Complete LT1 dropouts come with the intake, accessory drive, harness, sensors, and often the matching transmission. A stock LT1 makes mid-400s at the crank, a cam puts it in the 500 to 550 range at the wheels, and the factory GM ECU can be reused with our E92 conversion box instead of buying a standalone. The full comparison is in LS vs LT.

Step 3: Mounts and transmission

Our swap kits bundle the engine mounts, transmission crossmember, and accessory drive brackets for your exact combo, and each piece is available separately if you're building up from parts. Crossmembers exist for the T56/TR6060, the GM automatics (4L60E, 4L80E, TH400), and the DCT/8HP, with xDrive versions for the T56/TR6060, 4L80E, and 8HP.

On the transmission itself: the GM boxes are the well-worn path, the 335i's own GS6-53BZ 6-speed works with a PMC adapter plate, and the ZF 8HP is the modern automatic option with MaxxECU control. The transmission section of the parts list breaks down all nine options with what each one needs. For the 8HP, our guide Why the ZF 8HP Is Perfect for Your E9x LS Swap covers that swap end to end.

Step 4: Fuel, cooling, and accessories

The stock fuel system is returnless at 72 psi and feeds about 400 hp as it sits. One high capacity in-tank pump covers 400 to 600 hp, dual pumps past that. Pump control depends on your ECU: MaxxECU can keep the factory EKP module, Holley replaces it with a relay. The wiring diagram and pump options are on the fuel system page.

The stock radiator and PWM electric fan handle most builds. On the engine side you'll pick an accessory drive spacing (Corvette, F-body, or truck) and decide on AC: the Sanden drive plus the CAN box keep cold air working through the factory buttons. Both systems are in the parts list, and belt routing is in the accessory drive instructions.

Step 5: Wiring and engine management

Plan this before you pull the stock engine, because the ECU choice drives the parts list. A standalone ECU runs the LS, and our CAN conversion boxes tie it into the BMW's network, covered in the next section. Nearly all of the chassis wiring happens at the DME box in the engine bay.

Three platforms we stock and run: Holley Terminator X Max (the budget pick with a huge tuner network, needs our CAN box, no cruise control), MaxxECU (native E9x CAN so it doesn't need a box, cruise works, controls the 8HP), and the Haltech Nexus Rebel LS (built for LS swaps, cruise works, pairs with our Haltech CAN box). The ECU comparison lays out the tradeoffs between all three. Wiring is documented connector by connector in the wiring guide and on video in the Holley wiring walkthrough.

Electronics and CAN bus: what keeps working

The E9x runs nearly everything through BMW's CAN network, and the swap leaves the chassis side of that network alone. The factory modules keep talking to each other like they always did. The CAN box, or MaxxECU's native CAN support, joins the new engine to that conversation. After the swap:

The swap doesn't touch windows, locks, radio and iDrive, heat and defrost, or the convertible top on E93 and E88 cars. Interior functions stay close to 100 percent.
The CAN box brings back the factory tach, the 335i oil temp gauge (repurposed to read coolant temp), wheel speeds fed to the ECU, the factory AC buttons requesting the compressor, starter function through the BMW ignition, and a clean dash with no brake or DSC lights on RWD cars.
Cruise control depends on your ECU: MaxxECU and Haltech support it, and the CAN box converts the factory stalk into Holley LCD switch inputs.
You lose DSC stability control, precise automatic AC temperature blending (you still get cold air on demand, the compressor is just clutched now), and OBDII readiness. Manual conversions also want a little coding for reverse lights, covered in the reverse lights guide.

Step 6: Driveline

The BMW differential stays. Our adapters mate it to the GM driveline: the 335i/135i large case diff is the strength pick with the most LSD options, and the 325i/328i medium case holds up fine at moderate power. Between them runs a custom single-piece driveshaft, measured after the drivetrain is sitting at final height on torqued mounts. Big power and drag builds swap the BMW diff for our Ford 8.8 kit instead. Start with driveshaft basics, and read the rear knuckle and hub guide before you touch the rear end, because the 325i/328i and 335i hubs are different sizes.

Step 7: First start and sorting

Fuel pressure, grounds, and coolant bleed cause most first-start problems, so check those before anything exotic. The 4-part video series shows the whole swap on a real E90, including the small stuff written guides skip. After it runs: reverse lights take one wire and some coding (here's how), some cars want a small cluster recode, and then it's just tuning and seat time. When it drives, submit your build and get featured with the rest.

Questions

Cost, brakes, what still works in the interior: the FAQ answers the ones we get every week. Anything else, use the contact form or email Sales@lse90.com.