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E30 M3 (1986-1991) {Euro 86-892.3L: 200hp @ 6750} {1990 2.3L Evo2/Cecotto/Ravaglia: 220/215/215hp @ 6750}
{1991 2.5L Sport Evo: 238 @ 7000} {US -- 88-91 2.3L: 196hp @ 6750, 170tq @ 4750}
Total produced: 5,280 US, ~13,300 Europe/world


 
 
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Old Sun, Apr-05-2015, 04:30:37 AM   #1
peter*g
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Default Building an E30 M3 gravel rally car :-)

Some of you likely saw a '90 M3 rolling chassis show up on Bring-a-Trailer auctions late last year. The bidding climbed surprisingly fast with people trying to score a cheap starting point for a restoration project.

Well, much to the chagrin of a number of other bidders, I was the lucky buyer.

Some folks were upset that I won the car; not just because I scored the chassis, but also because of what I plan to do with it: the ratty M3 Roller Project is being turned into a no-holds-barred Group 5 rally car.

“Sacrilege!” some of you may say. I can not tell you how many people tried to convince me to accumulate original parts and make this thing garage queen. I was barraged with negativity from the E30 M3 purists, upset that yet another car is being “lost” to racing.

To that, I say, “THBPBPTHPT!”

The M3 is a homologation special. That’s a fancy way of saying, “built to be a race car”. I have the opposite view of the purists; every E30 M3 that doesn’t get it’s neck rung on a regular basis is a travesty to me. This is my idea of the correct use of all M cars:



Before the auction came up I was already planning to build an E30-based rear wheel drive rally car – going so far as to even pick up an ‘84 325 to act as a basis for the build. The chance to build a rally monster around an M3 (saving a ratty old chassis in the process) was too good to pass up. In fact, the missing M3 subframes, brakes, and engine didn’t phase me, as using stock E30 parts never even came into the equation for me.

As many others have done before, I plan to combine the light weight and short wheelbase of the E30 chassis with the superior driveline, suspension, and brakes from more modern BMWs. In my case, I’ll be adding the subframes, suspension parts, steering rack, and brakes from the Z3 and the 3.0l motor, transmission, and differential gearing from the ‘95 US M3. This will give me durability and reliability in a car with a power to weight ratio better than 9:1. I helped build a similar car for Targa Newfoundland 10 years ago and always wanted to recreate that car for gravel.


Starting the Build

The M3 project made it’s way to me before the holidays, and we have begun the long process of converting it into a competitive racer. The first step was to get it on a frame rack and see just how bad the obviously-repaired right front corner is.



The car had clearly been hit very hard on the right front at some point (hard enough to bend the passenger side floor!), and was repaired by cutting away the old frame rail and grafting in a new section.



Unfortunately the repair was pretty poorly done, and not only is the chassis still clearly twisted but the weld was sloppy and the metal at the seam is rusted and thin.



Rally cars need to have stout bodies to deal with the stresses of competition, so the repaired sections will need to be re-done before we do anything else. Thankfully, much of the sheet metal is still available through the dealer or specialty parts suppliers. We’re basically going to graft in a new right front corner from new old stock parts.



It’s at this point most people would have run screaming from this project, but in my case this isn’t a big deal. Why? Well, unlike most restorations a rally car needs to be fully seam-welded in order to not literally tear itself apart from vibration and shock. Adding a $1000 worth of additional sheet metal is no big deal when we were going to have to hand weld each section already anyway. Thankfully I have a great build partner in Nate Walton of Bay Street European, who is not only a master technician but an artist with a welder.

The project may seem daunting to some, but the plan is fairly straightforward:
  1. Repair the body, strip it down, seam weld, and then adjust/reinforce the suspension mounting points to accommodate our newer suspension parts and Reiger rally coilovers. Once fabrication is done, we’ll send the body for blasting and then on to the cage builder.
  2. While the body is away, rebuild the suspension, steering, and brake parts we’ll reuse from the Z3 while collecting all of the new parts we’ll need (control arms, bushings, bearings, etc.). We’ll also reinforce the subframes and trailing arms to deal with the abuse of gravel stages.
  3. Rebuild the donor engine, refurbish the transmission, and source an appropriately geared and built differential.
  4. When the cage builder is complete and the car is repainted, we’ll begin the assembly process; first suspension and brakes, then driveline, and the last step will be plumbing and wiring. As a proper rally build we’ll be doing some fancy things here; including a race dash and limited wiring harness, all stainless braided brake lines throughout the car, custom pedal box and hydraulic handbrake, and even a kevlar-reinforced stock fuel tank.
  5. The last order of business will be rally prep; installation of safety gear and fire system, mounting of spare wheel, triangles, jack, and tools, and installation and sorting of all of the odds-and-ends that go into a competitive build.

The goal is to race the M3 in a national rally event before the year is out. That’s a tall order given the state of the car today (and with this being a weekend project), but it’s not unreasonable. I’m grateful to have the help of Bay Street European in San Rafael, CA to speed efforts along. The car will be a “shop project” of sorts; giving the guys something interesting to work on outside of the maintenance and repair work they do on late-model customer cars all day.

Stay tuned to this thread for updates on the build. I’ll be posting all of our progress along the way, including an in-depth look at the mechanical and fabrication work we do to get the car rebuilt and competitive. I hope it’s entertaining and an inspiration to all of you to build something you love.
__________________
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- peter*g

.'02 E46 M3 (GTS roadracer)
.'96 E36 M3 (Dinan S3)
.'90 E30 M3 (rally racer)
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Discussing Building an E30 M3 gravel rally car :-) in the E30 M3 (1986-1991) Forum - {Euro 86-892.3L: 200hp @ 6750} {1990 2.3L Evo2/Cecotto/Ravaglia: 220/215/215hp @ 6750}
{1991 2.5L Sport Evo: 238 @ 7000} {US -- 88-91 2.3L: 196hp @ 6750, 170tq @ 4750}
Total produced: 5,280 US, ~13,300 Europe/world at BMW M3 Forum.com (E30 M3 | E36 M3 | E46 M3 | E92 M3 | F80/X)