If you've seen the latest episode of the LS3 E30 project (CLICK ME!) you'll have seen the lads got Tuning Fork to tickle the keyboard and liberate 250kW (335rwhp) at the wheels from their stock 6.2-litre LS3 V8. So why does "everyone" on the internet think they are boring and crap if they such a popular swap into other cars?
I have owned half a dozen E30s myself, and so I understand some people would be disappointed in the choice of an LS as it is such a common swap and there are so many great engines which fit into E30s, like the manic 5-litre E60 M5 V10, the S54 E46 M3 in-line six, or late-model turbo N-series sixes, but engine swaps have to take into account many factors beyond simply identifying a cool, powerful motor.
E30 afficianados understand the four-cylinder models are renowned for their much better steering feel compared to the six-cylinder models. The over-simplified theory behind this is that the lighter the front-end of the car you're driving is, the better steering feel and front-end handling will be - obviously this is a massively simplified statement, but if you have a car with 100kg over the nose it will steer, handle and stop better than a car with 500kg over the nose.
The next area to think of is where the car carries that weight. If you have 2 examples of the same car, both with 100kg engines up front, and one carries that whole 100kg up top and out front (say, under the badge on the front) then basic physics tells us it won't handle as well as a car where the 100kg is mounted low in the chassis and as far back as possible.
Check out the above image of an LS3 (left) compared to an MX-5's stock four-cylinder. While many think of a "V8 swap" as being the quickest way to ruin a car's handling, the fact is the all-aluminium versions of the LS V8 are actually quite light and compact, with the bulk of their mass centralised and carried low. With the short overall length of V8 engines (they're just 2 four-cylinders next to each other), and the lightweight top-end of the LS this means there is only a tiny weight penalty to pay.
Compared to a 2JZ or Barra, which are longer and much taller, with more involved plumbing required, the LS actually moves the engine's weight lower and further back in the chassis. Yes, you could move the engine by recessing the firewall but now your heater box doesn't fit, the transmission tunnel will need to be custom-fabbed, and you won't be able to use off-the-shelf parts, which means a months-long build. How you work on the car can then also become a chore - can you lift the rocker cover off in the car?
Overhead cam engines also pay a huge penalty with the size of their cylinder heads, as seen below with a four-litre Toyota 1UZ V8 compared to a 5.7-litre LS1 and, when you're swapping these engines into a car you need to think how hard (and expensive) it will be to custom-make an exhaust to fit around steering linkages and crossmembers.
I can tell you from personal experience it is not simple to fit a well-designed exhaust into a UZ-powered E30, and you still end up with less power at the crankshaft than Black Ch-OPS has at its rear wheels! Modifying a UZ V8 is also more expensive on a dollar-spent-per-horsepower-gained factor than an LS.
So physics tells us the LS is a good theoretical swap for the E30, but practicality-wise how does it stack up? The lads took 5 days to turn the car from a stocker into a 250rwkW V8 monster, which they simply couldn't have done with the high-tech late-model BMW motors as their complex wiring and computer control requires intense work to make work as you can't simply get an off-the-shelf harness and computer to plug in and run the variable cam control and valve phasing. They're great engines, but not as cheap as the LS, easy to source, or make work so why put themselves through that hassle?
Many people are outraged Marty didn't choose a 1JZ or 2JZ. Ignoring the issues with nose-heavy weight distribution, sourcing a good, running JZ engine is an expensive process today, and many will need to be pulled down and require work as these are 20-year-old engines today that will have hundreds of thousands of kilometres on them so piston rings, valve stem seals, turbos and engine bearings will all need to be inspected or replaced before you strap a big ol' spooly boi to the side and send it to 11ty. Not a build you can do in 5 days for the same money as the LS3.
The 2JZ is capable of insane power levels, sure, but the LS3 is also no slouch. With upgraded valve springs, cam and pushrods it is easy to make over 400rwhp (300kW), while there are multiple bolt-on supercharger offerings (like the Harrop Engineering TVS2650 below) that will reliably make over 700rwhp (over 520kW at the wheels) with a cam and E85 but on an otherwise-stock LS3. The spread of that power will be broad and smooth, improving the on-road driving characteristics, too.
While I do like V8s I do happen to have an old, tired BMW M20 six-cylinder engine from an E30 featured on a popular Aussie YouTube show sitting under a workbench, waiting for the day I find a series 1 E30 coupe not entirely made of rust (good luck, I know) to put it back into. For that particular car I want a howling aspirated six that is way up there on the PuRitY scale, and for Marty he wanted a quick, simple, reliable and powerful engine in his E30, which could skid its leiderhosen off at will but still handle nicely.