The M10 and M20 engines are designed around some old technology and the M42 engine is hampered by a small displacement. Turbocharging is not a valid option in some states (such as California). That leaves one option for increasing the horsepower of the E30: an engine swap.
The later 3-series engines, the M50 and S50 family, are easy to swap into an E30. This car has an S50 from a pre-1996 E36 M3.
Luckily for BMW enthusiasts, the company has used only a few different bellhousing bolt patterns and engine mount locations over the years. But before you get too excited, remember that any engine swap is a custom endeavor; even if it’s been done 1,000 times before, there are always small details that trip you up during the install process. What works for one car may not work for another, because of differences in engines and chassis.
With around 240 crank hp, the S50 and later S52 make great E30 powerplants. There are some tricks to the swap—mostly electrical, but they are straightforward and well documented.
The S38B38 “big six” engine from an E34 M5 can be swapped into an E30 but it is not an easy swap. The engine weighs about 100 pounds more than an M20 and the mounts, driveshaft, plumbing, and electronics all have to be fabricated.
This Tech Tip is From the Full Book, BMW 3-SERIES (E30) PERFORMANCE GUIDE 1982-1994. For a comprehensive guide on this entire subject you can visit this link:
The E30 engine bay is large and many engines, both BMW and non-BMW, have been swapped into it over the years. The BMW V-8 and V-10 swaps, while impressive, are difficult and the power advantage is not as great as the complexity of the swap.
Since an engine swap requires so much time and work, it does not make sense to swap in an engine that is only slightly more powerful than the E30 engines, such as the M50B25 and 28. Generally speaking, the best engines to swap into the E30 are the E36 M3 engines, S50B30 and S52B32. Both produce enough power to make the swap worthwhile.
The S54 from the E46 M3 is rated at 330 hp. It’s size, light weight, and power make it an attractive E30 swap candidate. However, it is not an easy engine to install. (Photo Courtesy BMW Group PressClub)
The simplest way to swap these engines into an E30 is to use the ECU and wiring harness from a pre-1996 325i, since this harness is simpler than the M3 harness that normally runs these engines, which has EWS (anti-theft). This converts the engine from OBD-II to OBD-I, which adds power and reduces complexity.
Unfortunately this conversion is not a simple electronics swap. Nearly every sensor on the engine and many hard parts, such as the intake manifold and fuel rail, must be changed as well. It’s not impossible, but there are numerous small details that have to be addressed—and this is before even beginning the process of installing the engine.
The only oil pan that fits an E30 must come from a E34 535i, as no other oil pan has the sump in the right location to clear the subframe. For reference here are the parts needed to swap the oil pan:
550/552 Oil Pan Swap Parts List
Oil pan: PN 11-13-17-40-346
Oil sump gasket: PN 11-41-17-03-947
Oil pickup tube: PN 11-41-17-48-150
Dipstick PN: 11-43-17-20-875
Dipstick tube PN: 11-43-17-38-169
Dipstick O-ring PN: 11-43-12-87-541
You don’t have to buy new parts, but they can be hard to find since there is only one car that can donate them. The other necessary parts are E36 mounting ears (these should have come with the engine if you are using an S50 or S52).
The S50/S52 engine bolts to the E30 Getrag transmission using the stock 325i clutch and single-mass flywheel. However, your transmission will be at a 10-degree angle to the right and will require some modifications to the transmission mount. If you use an E36 Getrag 250 you will not have to modify the transmission mount.
Once you have an engine and wiring harness you can begin installation. The brake booster on an E30 does not clear the intake manifold, so you have to swap to an E21 booster or a Porsche 944 booster. The E21 booster allows you to retain your stock master cylinder.
The exhaust system has to be custom made (the E36 M3 manifolds will clear the E30 chassis with some tweaking); the right control arm bushing, sway bar, and rear crossmember are the tightest points. The rest of the exhaust (or at least the part that connects to the E30 tail pipe) has to be custom made.
There isn’t enough room in this book to cover every single detail of an M50/S50-type swap but this should give you enough information to start your own research to determine which parts are needed for your particular combination of engine and transmission.
This shot tells a different story. The entire E30 subframe has been cut away and a tube replacement made. (Photo Courtesy Ryan Gangemi)
Not only has the car been modified, the factory S54 oil pan has been extensively modified to clear even the minimalist new crossmember. (Photo Courtesy Ryan Gangemi)
Here’s another angle showing just a tiny bit of the fabrication needed for this swap. Additionally, the engine has a very complicated ECU that must be modified or replaced.
The E30 driveshaft is a two-piece driveshaft with a rubber coupling and single U-joint for the front half, a solidly mounted center support bearing with a section of sliding splines in the middle, and a rear U-joint. The center support bearing and front rubber flex coupling are replaceable but the two U-joints are swedged in place in the factory driveshaft. (Photo Courtesy Vorshlag Motorsports)
Hard urethane engine mounts can make custom swaps easier by maintaining tight clearances between the engine and parts of the chassis. They can also be modified to situate the engine at any height. (Photo Courtesy Vorshlag Motorsports)
Written by Robert Bowen, author of BMW 3-Series (E30) Performance Guide 1982-1994