So you want to build an E30 track car, huh? Well, I don’t know you personally, but that might be the best idea that you’ve ever had. From a fun-per-dollar perspective, anyway. The E30 is truly one of the best possible chassis to transform into a certified track classic. Lightweight, direct, and communicative, agility is the name of the game here, forget about power figures.
While the E30 is a prime canvas to work with, there are a lot, and I mean A LOT, of considerations that go into building a competent E30 track car. Here, we’re going to cover the basics, including choosing a donor car, picking the right powertrain, dialing in suspension, finding the right wheels and tires, making sure you can stop effectively, stripping out as much weight as possible, and ensuring you’re as safe as possible.
Since the National Auto Sport Association’s Spec E30 class is the most respected E30-specific racing series and has set out tried and true guidelines for building a well-rounded E30 track car, I’ll be referencing their guidelines quite a bit. They set out to outline the best way to build an E30 track car for the least amount of money, and I respect and agree with their part choices and build specs. With that being said, a Spec E30 car might be a bit tame for some track veterans who are looking for a more visceral experience, so I threw in some recommendations for those folks too.
Choosing a Donor
One of the first things that you’ll need to sort out is what type of E30 you’re going to begin your journey with. Duh. While that might seem like a pretty straightforward task, there are a couple of factors that complicate things a bit. If we are going off of the guidelines set by the National Auto Sport Association for Spec E30, any 1984-1991 E30 that was made available by BMW through its authorized dealer network is eligible to compete in the series. Obviously, if you aren’t planning on conforming to Spec E30 guidelines, screw the rules.
So, with that requisite, there are a total of 8 different E30 variants to choose from, each with their own benefits and shortcomings. In the next section, I’m going to cover the basics of choosing between E30 variants and their different pros and cons for a track build but I’m not going to go into too much detail. If you want to learn more about the differences between E30 variants and pretty much everything else you need to know about the E30, check out my BMW E30 Buyers Guide.
Let’s start by talking about 4-cylinder models. 4-cylinder E30 models include the 318i and 318is, with the 318i using either an M10B18 or M40 and the 318is utilizing the M42. Okay, now for the pros and cons.
The good news is that the 4-bangers are extremely light, removing around 220 pounds from the curb weight of the M20 cars. The bad news is that even the most powerful 318is E30 variant produces a measly 134 horsepower. It goes without saying that horsepower is even remotely the biggest factor in an E30 track build, but if you are planning on conforming to Spec E30 guidelines, you’ll be at a significant performance disadvantage compared to 6-cylinder cars, barring ETA models.
For that reason, if you are planning on keeping the factory powertrain and aren’t looking to engine swap, the 318is is truly the only 4-cylinder E30 worth buying as a track car. While the M42 might not be the most powerful engine, they are a hoot. 318is’ got the name “Baby M3” for a reason, as the high-revving 4-banger is the closest that you can get to an S14 in a standard E30 chassis.
With the 4-cylinder cars out of the way, we have the 6-cylinder models to deal with now. In the US, we got the 325, 325e, 325es, 325i, 325is, 325ix, and 325ic models, all utilizing some variant of the M20 engine. This is where things get interesting again, as there are certain models in the 6-cylinder range that you want and some that you should definitely avoid.
Starting with the models that you should probably look past if you are planning on sticking with the factory powertrain. The immediate no-go models include the 325ic and 325ix. The cabrio is a no-go as it weighs a couple hundred pounds more than a coupe while also having less chassis rigidity due to the lack of a roof, both issues for a track car. You should also pass on the all-wheel-drive 325ix (unless you are planning a rally build) unless you like rampant understeer and slower lap times.
That brings us to the ETA models, including the 325e and 325es. The lower revving 2.7L M20s found in the ETA cars also use far more restrictive cylinder heads and inferior valvetrain components, hampering performance significantly. They are good candidates for stroker builds, but in factory form, they aren’t optimal track cars.
325i and 325is models are by far the best donor track car variants. The M20B25 is hands down the best factory E30 engine from a performance perspective. For that reason, if you are participating in a near-stock class like Spec E30, you’ll have the best competitive chance from a 325i or 325is.
There are some other important considerations that you’ll need to think about besides just the model of E30 that you choose as your blank canvas. The state of that canvas also matters a substantial amount. The condition of your donor car can determine the difference between a fun project and a wallet-draining nightmare, especially if rust is involved.
It’s important to recognize that E30s are over 30 years old at this point and old BMWs don’t have the best reputation as far as rust resistance and holding up to the elements are concerned. Most established racing programs have safety inspections that ensure that the vehicle is structurally sound, with rust being the main disqualifier. Instead of spending a small fortune on rust repair, it is far more worth it to just find a rust-free E30. Here are the places that you should look for rust before pulling the trigger on one:
- Jack point pinch welds on either side of the car
- License plate light bezel
- Floor pan
- Rocker panels
- Battery tray (can be found in the trunk on the passenger side and in the engine bay)
- Rear subframe
- Rear shock tower
- Tail light bezels (also check under the trunk carpet around the tail light area)
- Rear fender arches
You should also make sure that the car that you end up buying doesn’t show any signs of major structural damage in the past that could be dangerous in a track setting. Check the car fax for any serious accidents that may have resulted in frame damage, as untrustworthy frame repairs could cause serious safety issues in the future. I won’t go into all of the specifics of finding a quality E30 here, but if you want to know more, read my E30 Buyers Guide where I cover the subject in more detail.
Powertrain Refreshes, Swaps, and Light Modifications
By now, I’ve mentioned that power is one of the least important aspects of building a fun E30 track car and I stick by that statement. The real sources of fun come in the form of suspension and chassis mods which we’ll get to in a second. With that being said, it is very important to have a well-tuned and prepped powertrain, whichever engine that may be, that can reliably handle track duty.
This is another area where you’ll have to make some important decisions. If you are intent on sticking to Spec E30 guidelines, you’ll have to make do with all factory engine components with the allowance of up to a 0.020 overbore and a horsepower cap of 160.9, which is right around where a well-tuned and refreshed M20B25 will end up. In that case, the name of the game is making sure that every aspect of the factory engine is as in-spec as possible.
If you aren’t looking to abide by Spec E30 rules then you have even more decisions to make, especially if you do want more power than a lightly modified factory engine can provide. E30s are one of the most swapped classic BMWs for good reason. There is plenty of space in the engine bay for everything from an S50/S52 to an M62 or even a Chevy LS. Of course that takes a lot more cash and dedication than building out an M20 or M42.
There are also forced induction and franken-build options for factory E30 engines as well. The M20 is notoriously good at holding boost, and stroker builds are also very straightforward and can be done with all OEM hardware. Let’s discuss some of those options.
Spec E30/OEM+ Powertrain
For simplicity’s sake, I’m just going to approach this section from the standpoint that you have an M20B25 to work with, but most of the advice here applies to the other factory E30 engines as well. Spec E30 is very strict when it comes to engine modifications and doesn’t permit any aftermarket bolt-on components if you want to compete. However, every component in the engine can be refreshed to get it as close to factory performance as possible.
Most serious competitors in the class take that to heart, rebuilding their engines as far as their budget allows. The most important rebuild considerations include a fresh rebore (no more than 0.020 overbore), remanufactured cylinder head including new valves and springs (with everything being re-speced to factory standards), a new camshaft and rocker arms, and a fresh tune. Obviously, various gaskets, bolts, and seals can also be replaced as needed. With those refreshes, you’ll have an M20B25 that comes very close to the maximum horsepower cap.
Spec E30 also mandates that you use a specially designed Spec E30 exhaust which includes a forward section with collector, a middle section, and a muffler/tailpipe assembly which has to be purchased from Paul Poore who you can call at 267-374-8365.
If you aren’t looking to conform to Spec E30 but want to keep the factory powertrain in OEM+ form, there are a couple of aftermarket modifications that are worthwhile including a performance chip and a cam upgrade. If you want to learn more about quality OEM+ M20 upgrades, check out my M20 Performance Upgrade Guide.
E30 Engine Swaps
I won’t go too deep into E30 engine swaps here, mainly because I’ve already written an entire article about the subject. However, it is still important to mention that E30s are great candidates for a massive array of swaps from relatively simple 24v swaps to hulking V8 swaps. As I covered in my guide, the most common and worthwhile E30 engine swaps include engines like the M30, S50/S52, M52, M54, and S54.
The complexity and cost of those swaps depend on the age of the engine, as well as how sought after the engine is, with engines like the M30 only costing around $500 and being a nearly plug-and-play swap and engines like the S54 costing around $5,000 and requiring extensive modifications in order to work in an E30 chassis. It all depends on your budget and what you are looking to accomplish from your engine swap.
When choosing the right engine to swap into your E30, there are a couple of important considerations that you should think about outside of just cost and complexity. E30s are very well balanced from the factory, which is also what makes them such great track cars. If you’re planning on going all out with an M62 or LS engine swap, you have to think about how those heavier engines will change the handling characteristics of the car. There are ways to counteract that, but that usually involves adding more weight as ballast.
Power-to-weight is also very important to consider, as it doesn’t take much to make a very quick E30. 300 horsepower in an E30 can feel like 500 or 600 horsepower in a heavier car, so take that into account before going truly hog wild.
Forced Induction and Strokers
The last powertrain option involves heavily modifying the factory E30 powertrain. The M20B25 is a fantastic engine to turbocharge. An unopened M20B25 is capable of supporting around 300 boosted horsepower reliably and the bottom end is capable of around 400 horsepower without issue. The B25’s lower 9.7:1 compression ratio is the key to its ability to hold boost better than any of the other factory E30 engines, except for maybe the M42, which comes with a factory-forged crankshaft and rods.
The M20B27 is a far less ideal engine to turbocharge in factory form. Its higher compression ratio, in addition to its restrictive “200” cylinder head with smaller ports, tamer camshaft, and softer valve springs make it a lot less capable than the B25. Not to mention the B27’s lower redline, which prevents boost from being built fast enough for turbocharging to be worth it. However, that is where mixing and matching engine parts comes into play.
While the M20B27 is the worst candidate for boost out of the gate, it is the best engine to stroke. From the factory, the M20B27 is a 2.7L engine compared to the 2.5L B25. The cylinder head is really the B27’s true weakness, but it is possible to swap an “885” cylinder head (from a B25) onto an M20B27, which increases displacement to 2.8L while raising the redline and decreasing the compression ratio dramatically.
That is by far the best way to create an M20 stroker, which also happens to be the best engine to turbocharge. I have owned a non-turbo 2.8L M20 stroker E30 for years now and I find that the additional power is just where I want it personally.
Now that we have powertrain considerations out of the way, it’s time to move on to the fun stuff. Of all of the elements of an E30 track build, suspension is truly the bread and butter. In fact, I’d argue that you can build a pretty decent E30 track car with only suspension-related modifications and nothing else. So, what are the main suspension upgrade options? When it comes to track-appropriate suspension setups, the main two options consist of a nice spring/shock combo or coilover suspension.
Once again referencing Spec E30 guidelines, they allow both spring/shock combos and coilover options depending on your preference. The Spec E30 spring/shock setup is a set of Bilstein B8 Sport Shocks combined with a standardized set of fixed spring rate H&R race springs. In terms of pure handling, this is one of the best setups available for any E30. It is a tried and true combo of class-leading parts that ensure flat cornering while also being soft enough to daily drive on without any discomfort. Spec E30 also allows for camber plates and unrestricted camber adjustments so you can dial in your setup to best suit you.
Spec E30 also offers a coilover conversion option, which works in combination with the factory struts. Ground Control actually makes a kit specifically for Spec E30, which is the only approved coilover option for the class. Coilovers are beneficial as they allow for ride height adjustments which you don’t get with an upgraded spring/shock combo. If you aren’t conforming to Spec E30 guidelines, more advanced coilover systems will provide the best handling characteristics on track, but they aren’t the most comfortable on the street.
Other Suspension-Related Mods
Suspension modifications span outside of just shocks and struts. There are many other important suspension-related modifications that also have a serious impact on how a car handles and are important to think about when building an E30 track car.
Anti-roll bars are a crucial component when it comes to dialing in a car’s suspension geometry. Anti-roll bars link the suspension on either side of the axle via the control arms in order to significantly reduce body roll, a crucial component for a track car that needs to corner as flat as possible for the best lap times. Adjustable anti-roll bars enable you to dial that characteristic in even further, allowing for improved balance. Spec E30 prohibits the use of aftermarket adjustable anti-roll bars and only allows non-adjustable ones which get the job done just fine.
Bushings are another important point of discussion, as they can play a big role in handling as well as safety. E30s are old as sin at this point and it’s nearly impossible that any of the factory rubber suspension bushings are in good shape at this point. Replacing them is pretty much a requirement if you want your E30 to be competitive.
Polyurethane suspension bushings allow less suspension component play and keep suspension geometry in check. They can really tighten up the way that your E30 handles, especially when paired with a good set of coilovers. The main bushings that you want to pay attention to are front control arm bushings, differential bushings, trailing arm bushings, and rear subframe bushings.
I currently have polyurethane suspension bushings installed on my E30 and I could tell an immediate difference in steering directness compared to my old and worn-out suspension bushings. For a couple hundred bucks, it’s a worthy upgrade.
Wheels and Tires
Wheel and tire upgrades are not only one of the most important upgrades for a track E30 (second only to suspension upgrades) but are also one of the most expansive. There are so many wheel and tire options available for the E30 that you can get lost in a sea of choices. While there aren’t any wrong options, there are certainly some guidelines that you’ll want to abide by to get the most out of a wheel and tire combo.
Reducing unsprung weight is extremely important, as any weight that isn’t supported by a vehicle’s suspension (like wheels and tires) is especially detrimental to handling performance. For that reason, you want the lightest wheels possible on your E30 track car. The 4×100 bolt pattern used by E30s can be difficult to find wheels for, however, manufacturers are starting to accommodate the bolt pattern a bit more these days. Spec E30 mandates that wheels must be 15”x7” and be no lighter than 13 lbs, limiting options even more. However, there are still some good options out there like Team Dynamics Pro Race 1.2’s (which are also common Spec Miata wheels) or Kosei K1s.
Tires are also one of the most important factors in an E30 track car build, as they dictate how much grip you’ll have on track. The options are truly endless here, but there are a few tires that shine above the rest. Spec E30 uses 205/50/15 Maxxis Victra RC-1 for competition, which is an aggressive dry traction semi-slick race tire. Prior to switching to Maxxis, Spec E30 used Toyo RR tires of the same spec, which are also fantastic race tires.
All of the mods that we have discussed so far help an E30 go faster, but being able to stop effectively is obviously just as crucial. OEM E30 brake assemblies, including the factory rotors and calipers, can handle track duty if you upgrade other surrounding elements like the brake pads, lines, and fluid. However, upgraded rotors are a good idea if you opt to use upgraded pads (which you should) to help with overall performance.
The most important brake system upgrade that you’ll have to do at a minimum is swapping out the factory pads for performance ones. Race pads have the benefit of absorbing more heat generated while braking and take longer to reach their fade point. That is crucial on the track, where brake fade is the primary killer of lap times if you plan on doing more than a couple of laps in succession.
Drilled and slotted brake rotors are allowed in Spec E30 and also aid in venting heat away from the brakes themselves. Additionally, slotted rotors help release gasses built up from off-gassing brake pads, which prevents any delay when stomping on the brakes.
Smaller upgrades like upgraded braided metal brake lines and upgraded brake fluid can also make a big difference on the track. Stainless steel brake lines provide a quicker, firmer, more consistent pedal response by maintaining consistent brake pressure. Additionally, stainless steel lines provide precision brake modulation, especially during threshold braking. Switching to a brake fluid with a higher boiling point is another relatively inexpensive way to improve braking performance. The higher boiling point of upgraded fluid will prevent brake fade and other issues caused by overheating brakes.
E30s are already extremely light cars, especially by today’s standards. Depending on the variant, an E30 can weigh anywhere between 2,380-2,811 lbs from the factory. There isn’t a new car on the market that can get even close to that figure. The E30’s lightness is one of its biggest selling points as far as being a great track car goes, and the good news is that it can get even lighter!
Weight savings can be as extreme or moderate as you want, with some enthusiasts drilling down to the gram while others want to retain a relatively stock-ish interior while still shedding a few pounds. Regardless of your plans, I’ll break down what you can remove and how much weight you can shave down as a result.
The biggest ticket weight reduction items include swapping from early metal bumpers to plastic bumpers (pre-’88 cars -20 lbs), undercoating removal (-25+lbs), A/C compressor and brackets, lines, and wires (-50+lbs), front passenger and rear seat removal (-58+lbs), interior trim (-25 lbs), carpet removal (-15 lbs), removal of jack and spare tire (-30 lbs). There is more that can be removed, of course, but those are the major items that have the least impact on drivability. If you want to learn more about potential weight savings, there’s a great forum post with a breakdown of pretty much every item that you can remove and how much it saves.
Go-fast bits are obviously a big part of building a good E30 track car, and while safety mods aren’t the most fun, they are vitally important. Most racing series have their own requirements as far as safety requirements are concerned, and almost every racing series is extremely rigid and strict when it comes to meeting those standards.
The most common safety requirements for most organized E30 racing series include a six-point roll cage (with additional rules and regulations surrounding how that cage was installed and assembled), some kind of fire suppression system, tow eyes for quick retrieval should anything go wrong on track, code-approved lug nuts, firmly secured oil lines, up-to-code fluids, a kill switch, and an appropriate helmet and race suit. Once again, safety requirements can vary significantly based on the racing series, so it is important to thoroughly look over the requirements of the series.
In most cases, if you fail even one aspect of the safety inspection, you aren’t allowed to compete in the day’s event, so it is important to have everything dialed in before showing up at the track.
Have Fun and Enjoy Your E30 Track Car
While I did my best to outline most of the basics required to cobble together a pretty capable E30 track car, there is no perfect recipe. There are hundreds if not thousands of E30 track car threads on all of the major E30 forums and no two of them are the same. Building a track car always boils down to personal preference and your driving style, but the good thing about the E30 chassis is that it can accommodate any personalized build under the sun.
If you really are considering going deep on this adventure, I highly recommend reading about other enthusiasts’ E30 track day build experience. There is so much information out there about any potential modification, powertrain swap, suspension setup, tire choice, and everything in between. Since there are so many factors involved in the process, it is a great idea to see where other E30 owners have experienced issues, wished they would have gone another route, or found a better way to do things. Knowing those things beforehand will save you a lot of time and money in the long run.
Regardless of your individual goals, there is little chance that a purpose-built E30 track car will do anything besides put a massive smile on your face. It is a long and expensive journey getting there, but the results almost always pay off a hundred-fold.
If you enjoyed this article and are curious about other potential BMW track car options, I wrote a very similar article to this one on E36 track day cars. Take a look at that article and decide for yourself which is better for you.