The first step is finding a solid donor car. A 330ci or 330i with a factory manual transmission will take no small amount of effort to find, but will be the simplest to convert to a Spec E46 racecar.

A few years ago, I wrote a series on building a Spec E30 as an average guy, doing a home build in his garage. I don’t have a shop with a lift and tons of specialty tools to make the job easier. However, I have collected some specialty tools along the way. I suspect there are many out there just like me, who also wonder if doing a home build is feasible and cost effective?

Why Spec E46?

A spec class levels the playing field to some degree. There are some who have an unlimited budget and can afford all the best bits. That never changes but, at the end of the day, the cars are more similar than they are different, compared to a non-spec racing series. The more I looked at the rules, the more I learned that the class would in no way emulate the Spec E30 class in terms of cost. The required parts list carries a measure of sticker shock without a doubt. Coming from the world of Spec E30, I had to get used to the reality of the expense of some of the parts. It is a growing and popular series in many regions despite the cost of doing a build.

First, we had to find a chassis. Perhaps it’s too early in the life of the E46 chassis, but I can tell you I have bought running 325is chassis back in the day for $500 and built them into a Spec E30 for around $8,000. More recently, the only thing you could find available were 325E chassis, something for which you would pay $2,000. This won’t be the case for Spec E46, but I like a challenge! This won’t be a how-to-do-it-cheaply-and-affordably kind of story. This is more of a how to do it at home and what parts you should change and why. It’s also not a blank-check story, either.

The model needs to be a 330i or 330ci, but you can use 323, 325 or 328 variants, but you have to update it to be a 330i. You should look for a model year 2001-2005 sedans and 2001-2006 coupes. There are some model-change differences from the first years to the last years of production, but for the most part, nothing that can’t be dealt with. You cannot use the 330ix model or the ZHP optioned cars. Sadly, nor can you use a wagon. Yeah, that one hurt me, too. How cool would a wagon be! I digress.

I believe the ideal candidate is a 330ci manual five-speed coupe, slick top! The extra work saved by not having to deal with the sunroof and its added aesthetics make this, to me, a desirable car. Having said that, the slick top is rare. Seems that the average commuter really liked having a sunroof, and BMW sold a bunch of 330s with sunroofs. BMW also sold a ton of cars with automatic transmissions. So that can add some cost to a build if you were to find an automatic and have to change it for a manual. But it can bring the purchase cost of the car down if you find a running car with a bad automatic transmission! Using some strategy when on the hunt for a chassis can pay off.

The Hunt

It took a few months to find a car. When they do show up cheap, they sell fast. Once, when I was on my way to look at a car, I was notified via text that the car had just sold before I got there. Such a strange experience! The cost of a used car can vary. In my area, I found that most are listed from $2,000 and up.

All are in various stages of maintenance neglect, wear and tear and even abuse. But patience paid off and I was able to obtain an early 2001 coupe, five-speed with a slick top! The only downside was it had 190,000 miles on it. So the motor is probably tired and all of the rubber bits are done including the suspension pieces. And that’s OK because I’m building a racecar. Racecars don’t have rubber suspension components!

Sourcing New and Replacement Parts

The first thing to do is compile a parts list you need to be spec compliant, or competitive. That’s one list. Then you need to evaluate the car and find out what parts need to be replaced, or serviced. That’s the  second parts list!

For example, within the E46 world, I’ve learned that the VANOS cam-timing mechanism can cause issues and can need to be rebuilt. I researched doing the rebuild myself and buying a rebuilt unit. I chose to rebuild it myself.

Another failure point is the DISA valve. It’s an engine management device in the intake  that helps increase torque down low to help with “around town driving.” I’m certain it won’t affect the way the car drives on track at all, but if the plastic valve fails and gets into the intake, which they are known to do, then this is definitely another maintenance item that should be replaced before hitting the track. I can pay a little now, or I can pay more later. You know the story. I ordered a DISA repair kit too.

Those are the two main items I didn’t know about with the E46, and was glad to find out about them so I could make the needed repairs. I also ordered lots of maintenance items, hoses, pumps and what not, but I’ll get into that as I get to it in the build.

The seating and interior components in an E46 are heavy. Sedans and coupes have curb weights of more than 3,400 pounds, but the class minimum weight is 2,850 pounds, so there’s a lot of weight that can be pulled from these cars.


First thing first: The interior needs to be stripped, all of it, including the dash. That is a full day’s work in itself. There are a ton of fasteners, wiring and plastic bits all over the interior of the car. In addition, all of the airbags in the car needed to come out. I wasn’t aware of how many airbags and airbag sensors they crammed in that car! The obvious airbag is in the driver’s steering wheel and on the passenger side dashboard. Then there is a very long curtain of airbags on each side for the side-impact protection. Yellow airbag electrical connectors are all over the car. It was intensive. The amount of weight reduction from the interior alone, I’m sure is enough to cover the added weight of the cage.

Once all of that was done, it was time to remove all of the interior sound deadening material. Tar strips everywhere. I will say that with a little added heat it all came out without too much fuss, but there was a lot of it to remove.

The stock interior comes with a lot of sound-deadening tar on the floorboards and transmission tunnels. It comes off more easily by heating it or chilling it with dry ice

The next step was to gut the doors, for weight reduction and so the cage can extend into the space in the driver’s door for added protection for the driver. With the removal of one bolt, the doors are easily removable from the car! I love that feature and it makes working on the car in a confined garage much easier. Plus the neighbors love seeing racecar doors leaning up against the front of the house.

There is also a lot of wiring for body control modules and the side curtain airbags that came on the E46 cars. Yellow connectors are for airbags. Be sure the battery is disconnected when stripping the interior.

Gutting the doors while they’re off the car is much easier than trying to do it on the car. Using a cutoff wheel, I cut as much of the sheet metal away from the door as I dared. You need to retain some of the metal to keep the doors from flopping when open. I had the lovely experience of having the driver’s side glass shatter when I was trying to remove the lower hardware on the window regulator. Glass everywhere! In fact, I still find glass in the garage and in the car! It’s amazing how one window can fill up a 5-gallon shop vac! With the wiring and regulators out of the door, it was time to remove the factory reinforcement bars. They are actually nice pieces, but for my build it’s unnecessary. Remove the two bolts and out they come.

Removing the doors creates ample access to the interior.

The last step of this process involved the removal of the front and rear glass, because all of the glass needs to come out of the car to make it easier for the cage builder. You could leave it all in if you wanted to. If your cage builder is not careful, it’s easy to damage the glass when welding. Welding splatter can burn pits in the glass and ruin it. Plus it just gives the builder more room to maneuver and it overall makes the job easier for them to have multiple access points. I wish I had removed the glass before I stripped the interior. Some of the bolts are up against the front glass A pillar, which made for an awkward time with removal.

The dash and forward section of the center console come out all as one piece. According to the rulebook, “Stock dash must be retained. The portion of the dash extending below the middle trim strip may be modified or removed. The factory dash support may be removed.”

E46 glass is mounted to the car via a bead of silicone. It’s laid on the car and the glass is set on top of it and when the silicone cures, it bonds the glass to the car and seals it from the elements. To remove the glass, you will need a special tool, which is readily available from common online sources. The tool for this job is a roll of very thin wire and two handles. Another tool, which came with my kit, will push the wire thru the silicone and out to the other side. Install the handles on each end of the wire, one inside the car and the other outside the car. Then you saw back and forth, keeping pressure on the direction you want to cut the silicone. Make the cuts all the way around the windshield and it will simply lay over and can be removed easily. Mine was pitted from its 190,000 miles and likely will be replaced with a new one. The old one will make a nice spare. The rear window comes out the same way.

Next Steps

Cage! I don’t have a MIG or TIG welder, nor a bender, nor the tubing and plating. That just means I won’t be building this cage in my garage. Some things need to be outsourced. I’ve built cages in the past and I’m happy to have it done for me this time.  I sourced an experienced cage builder who is an hour drive away from me, a little pricey perhaps, but to me, worth it. He is not a cage builder. Oh no, he is so much more. He is an artist who does amazing work with his TIG and anything metal. I found some time in his schedule and dropped the car off at his shop for him to work his magic. We’ll pick this up in the next installment after it’s back from the cage builder.

The doors come off easily, which makes gutting them much simpler. There are no limitations to how the doors can be gutted, but remember they need to be structurally sound and must be able to be opened from inside and outside the car.
Image courtesy of Shawn Meze


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