You don't ruin cars by engine-swapping them, regards Workshop Manuel
The Internet has been awash with random people claiming Marty and MOOG have "ruined" their E30 BMW by replacing the 125kW 2.5-litre six-cylinder with a 320kW 6.2-litre all-alloy LS3 V8. However, I would wager nearly all the people raging online haven't actually driven an E30 BMW, let alone well set-up LS-swapped one.
The basis for a good engine swap is finding something easy to source, light and powerful that improves the car's dynamics in the way you want. Marty wanted a well-rounded street car he could take to track days and skidpans, but also something reliable and docile enough to drive to the Slop Shop for lunch, or up a twisty mountain road on a sunny weekend.
Because E30 BMWs have generous engine bays you can fit all sorts of cool engines into them, and this means personal preference comes into the discussion, because we all have our own preferences when it comes to motors. Some people love the rush of rotaries and turbo four-cylinders coming onto the power band, while others prefer the smooth torque and booming exhaust of a V8.
With so many potential engines you can jam into the tiny German rockets, I'll run you through some of the good - and bad - engines which have been jammed into E30s over the years.
Why should you care what I think? Well, not to toot my own horn, but I've spent nearly 20 years working as a motoring journalist, professionally reviewing cars for magazines and websites, and writing hundreds of feature stories on custom-built tuner cars, hot rods, street machines, pro tourers, and the like (PS: *toot*!). I have also owned a bunch of E30 BMWs as they are potentially my favourite car to own and do up, so I reckon I have a pretty good handle on how a well-sorted E30 drives.
When I say these cars have huge engine bays I'm not lying - that is a BMW V12 crammed into the front of an E30! OK, so a V12 is just two in-line six-cylinders having a snuggle but it still presents packaging issues for exhaust clearance around the steering, coolant lines, and more. In Australia we don't see these swaps because BMW V12s make about 6hp and even broken ones cost more than what most other good engine swap options start at. Guys in Europe have successfully swapped twin-turbo V12s into E30s, though that is an expensive way to make less power than a cammed LS...
While all manner of V8s have been swapped into E30s over the years the LS is potentially the most popular thanks to its small size, light weight, great power potential and ease of purchase. With most of the engine's weight low in the chassis and behind the front axle line the steering feel is still good and it retains the E30's wonderful sense of balance BMW endowed it with.
The trick with LS swaps is to not go nuts with big camshafts or massive power outputs as the engines make so much torque you'll easily over-power the E30's chassis and trailing arm rear-end. I know about over-powering E30s because I did just that when I put a cammed 6.0L LS into a 1989 E30 more than 10 years ago. The theory was 1000kg & 500rwhp, but the reality is it was too crazy to be a street car and too slow to be a race car.
While you'll get mad respect on Instagram for a 7000hp E30 the reality is it'll be a pig to drive... unless you're looking to build a drag car. Using the broad powerband of a stock LS3 means the MCM E30 can lope along in any gear as a civilised street car or fry the tyres off when you want it to. It also means you can get spares anywhere in Australia, and it will be reliable with easy service intervals.
It is these last two points which normally kills the option of fitting a multi-cam BMW, Toyota or Nissan V8, though these swaps have been done plenty of times over the years. Fitting the headers around the steering and the fat overhead cam cylinder heads is one issue, but the main reason people go LS over a multi-cam V8 is because they don't make great power compared to the purchase price. They're also not significantly lighter than the LS
People On The Internet also wanted to see a Honda four-cylinder, with most opting for the K-swap. To be honest this is a swap I haven't personally driven but I am very interested to drive one as I feel the K-series (turbo or aspirated) would be an excellent fit for the E30 platform.
Two of BMW's most beloved models - the E30 M3 and E30 318iS - both ran DOHC 4-cylinder engines and they allow for a wonderfully engaging driving experience that is the equal to any MX-5 I've driven. I believe Marty seriously considered a K-swap for his E30 before going down the LS route as there was more local information on how to make a RHD LS E30 work compared to a RHD K-swap (most of the kits are for LHD, which complicates the exhaust/steering clearance greatly).
If you ignore the exhaust note (V8 fan talking here) the SR20DET and rotary-powered E30s keep the wonderful steering and light weight, though the base price of these engines has been rising massively over the last few years. The power delivery of the smaller capacity engines can be quite tricky to tame in a street car but they deliver an amazing rush as they come on boost that no aspirated BMW engine could ever replicate.
Stories of maintenance issues for SRs and rotors aside, these are excellent options if you're wanting to engine-swap your E30 with a different engine. Just budget for an engine rebuild as the newest 13Bs and SR20s are almost 20 years old now!
I love JZ six-cylinders but I'm yet to drive a JZ-swapped E30 that retains the model's famous handling, steering and chassis balance. This is actually true for many "big-cube" six-cylinder swaps, as I've also driven a Barra-swapped E30 (far too nose-heavy), and the BMW M30 six (heavily compromised engine bay, heavy and not great power output).
The price of a good JZ motor also puts it outside the realms of most engine swappers today. You'll be paying thousands of dollars for a base motor, which will these days need to be opened up and checked through before you sling it into your swap car. The weight of the iron block hanging a long way in front of the strut towers blunts the steering feel and it will take bulk time refining the tune to have a single-turbo set-up come onto boost smoothly and cleanly so it doesn't violently overpower the rear-end.
Way back when I first started playing with E30s, approximately 16 years ago, the absolute God Mode engine swap was to cram the twin-cam S38 3.6-litre (or 3.8-litre!) out of a BMW M5 into an E30. As you can see in the pic above there is next to no room length-wise in the bay, even when you ditch power steering and air conditioning. The S38 makes truly glorious intake and exhaust noise but it turns the little E30 into a total lead-tipped arrow, the engine costs more than most people's whole car, they are maintenance intensive, and they are incredibly expensive to work on. But the kids on Insta will give you mad likes bra!
BMW's late-model turbo six-cylinder engines are a great option for a swap into E30s... if you can find one for a good price down here in Australia. Even the naturally aspirated M54-series six-cylinder engines from the E46-generation cars gives a stout increase in power, smooth performance and will bolt in.
While I'd argue this is the purist's choice for an E30 engine swap the tricky part of this conversion comes when you need to wire it up and get all the variable-rate cam control and valve control working, but it is definitely worth the effort to get all that electrospacewizardry going because it broadens the spread of power and makes the car much faster as there is grunt available all through the rev range.
An excellent entry-level swap for people new to E30s or working on cars is to fit an M50 or M52 out of an E36-generation 3 Series. These engines bolt in on factory mounts and require just a few wires to change from a single-cam M20 six-pot, but they grant you twin-cam six-cylinder smoothness, more power and the ability to make bulk grunt down the track with a turbo.
Short of swapping an exotic S-series M3 engine, the alloy M52B28 would be my 2nd favourite engine-swapped E30 to actually own and live with after an LS3 swap, as the M50/M52s can be swapped no time, have enough power to be huge fun, make great exhaust note, and yet still be cheap to build and run.
Finally there were some people asking for exotic swaps, like McLaren F1 S70/2 V12s or the 5.0-litre S85 V10 from the E60 M5. Brintech has actually fitted an S85 into an older BMW and found the finished product disappointing despite the fact it makes 500hp and revs to 8000rpm.
After you source one of these engines and have to pay for it, getting the electronics working is another expensive hurdle to overcome, let alone maintaining it or buying parts for such an exotic engine.