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Unread 11-21-2013, 05:52 PM
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Default Re: Vorshlag BMW E36 LS1 "ST2 Build"

Project Update for November 21, 2013: We got really busy in the shop back in September but finally got some time freed up to work on the ST2 project a little in October and a bit more time in mid November. Let's cover the progress to date...

Olofagus washing the hail beaten M3 "donor car" behind our shop. Those hideous headlights are for sale!

Donor Chassis Stripped and Sold

We had picked up this silver 1997 M3 4 door "donor car" shown above a few months back, which was a rolling chassis that had severe hail damage. I bought this one just to get the good M3 bits like the front spindles/brakes and rear subframe/trailing arms/hubs/uprights/LSD diff/halfshafts/brakes. We always upgrade the non-M E36 cars getting an LS1 V8 to the M3 limited slip diff, stronger halfshafts, and stronger/bigger brakes, uprights, etc. This subframe is held in place with 4 bolts and is easy to swap - these should sell for around $800-1200 if you get one from a junkyard. All 1995-1999 M3s used essentially the same bits, with the automatic cars having a different gear ratio than the manuals. We've used these with up to 490 whp and 315mm Hoosiers without breakage.

The 1997 M3 willingly gave up it's rear subframe assembly, chock full of dusty but stronger M3 goodness

We also managed to get some good OEM M3 bumper covers (front and back), side mirrors, seats, door panels and a few other cosmetic pieces. Much of this will be used on the ST2 chassis, which was a plain jane 1992 325is with an open diff and itty bitty brakes.

The guys cleaned up the interior, washed the exterior, swapped the parts with the 325's subframes/suspension/brakes/wheels, bled the brakes, and we put the 97 M3 up for sale on Craigslist for $700. I figured this clear titled, rust free M3 chassis would sell easily. Nope. Weeks go by, no calls. So we lowered it to $500. Nope. Then some friends came buy and bought the front grill surround and radiator support for $200, so we dropped it to $300. Finally got a buyer when we dropped the price to $200...?! Sheesh, tough season to sell cars, but at least it is gone AND we have a truckload of good parts to use on the ST2 build and even more bits to sell off separately.

We took our body dolly and modified it to fit the E36 chassis. You see we often get cars stripped down to the tub (to work on or replace the front and rear subframe crossmembers) and need a way to secure them to a mobile table, so we built the dolly. Then for each new chassis we use it on we make crossbeams that attach to the chassis in some way. The E36 crossbeams attach to the four "T-hook" mounts common to all E36 unibodies. Once bolted in place the chassis can't come teetering off the dolly, and it can go on and off quickly.

Subframe Reinforcement Work

With the chassis secured to the dolly we could then remove the front and rear bolt-on crossmembers, which went onto the 1997 M3. The M3 has a unique rear crossmember (it is stamped "M3" and probably has more steel in it than the non-M), which we stripped down to the core fabricated steel. The front crossmember was similarly deconstruced, and the control arms, uprights, swaybars, steering rack and differential housing were removed. These crossmembers were then dropped off at CrossLink Powdercoating in McKinney, where they glass bead blasted the subframes down to the bare steel.

The front crossmember (above at left) looked fine, and there is no "M3" version, but we wanted it in bare steel so we could reinforce it. This work consisted of our fab guys stitch welding some items in the fabricated factory steel assembly that otherwise had no welds. Other areas that were already "stitched" were instead seam welded, to add rigidity.

An E36 Front Subframe Reinforcement Plate kit (link) from RallyRoad was then welded in place. This kit includes two different types of laser cut plates. The first part goes under the stock motor mount plate (the top piece), shown below left. This more than doubles the thickness of this location that is reported to crack easily. The second laser cut plate spans a large open gap on the bottom side of the crossmember, under the main motor mounting hole. Both of these plates were fully welded in place.

The rear subframe got much of the same attention. Unwelded seams got some stitches of welds and stiched portions got full seam welds. We also added a 2nd RallyRoad reinforcement kit of more laser cut parts, shown below left. Normally the OEM style rear swaybar mounts off of two tabs that are cantilevered off the back of the rear subframe. This RallyRoad kit beefs up the rear swaybar mounting position on the rear subframe, triangulating and boxing it all together. I don't have a great picture of this installed, but you can see this boxed section in the below left picture.

After the subframes were welded up and reinforced we sent them back to the coater for a shot of gloss black powder coat, which is super strong and last much longer than wet paint. While the subframes were still out the crew here at Vorshlag reinforced the rear subframe mounts and RTAB buckets on the chassis.

The RTAB buckets in the chassis can rip out under extreme loads (giant R compounds + lots of power) so we used another RallyRoad laser cut kit for this section. This "C" shaped piece of plate steel is precision cut to go around the front mounting hole for the rear trailing arm. To install this the chassis was stripped of undercoating and paint, the entire section was seam welded then ground flat, the RallyRoad laser cuts were bolted in place, then they were fully welded around the perimeter. There are also 3 open holes in the C-channel where rosette welds are added. Then this entire area was sprayed with self etching, zinc based primer.

Another area of potential failure on non-M E36 chassis (and all E46 chassis) that you always need to address (dual purpose street/track or full race cars) is at the rear subframe mounting positions on the unibody. These mounting points can crack and even rip out (not pretty!) under lots of load (grip + power) as well as from normal street driving if you have worn rear subframe bushings (they all wear out). BMW figured this out and added double-thick reinforcement plates to the E36 M3 chassis at the factory. These stamped steel plates can be purchased from BMW, which is where we got the ones from this car. The entire subframe has to be out of the car, then these areas have to be stripped to bare steel, these plates seam welded into the 4 mounting positions, then primed with the self etching primer. A must for all non-M E36 cars.

Pictures showing E46 BMW rear subframe mount damage (left), then repaired/upgraded by Vorshlag with a Turner reinforcement kit (right)

This is a chronic problem on ALL of the BMW E46 3 series chassis (see the cracks in an E46 M3 we repaired recently, above), as BMW neglected to reinforce these chassis at the factory and the used seemingly even softer rear subframe bushings. BMW lost a class action lawsuit due to this issue with the E46 chassis, too. We've seen entire trunks ripped out when this problem was ignored for long periods. We do a number of these E46 rear subframe mount repairs and reinforcements every month here at Vorshlag and after dozens of these repairs we have never seen a car that DIDN'T have cracks in the chassis - even super low mileage, totally stock cars. 100% failure rate on the E46.

More E46 BMW rear subframe mount repairs/upgrades

We only recommend using polyurethane subframe bushings for the E36 and E46 chassis, from sources like Powerflex; do not replace worn out OEM rubber bushings with more rubber bushings. We are a stocking dealer for Powerflex and they offer two types for the E36 chassis: the Purple street and Black race versions. The E46 above had some of the streetable versions, which are still considerably stiffer than the OEM rubber bushings. The stock rubber bushings have large air gaps and allow for far too much subframe-to-chassis movement, which eventually causes the chassis cracking problems.

On the ST2 E36 rear subframe (above), after this piece came back from the powder coater we installed the Race (black) Powerflex poly mount bushings. These are pretty stiff and only have the slightest NVH reduction over aluminum mount bushings. The diff cover mounts are aluminum and were sourced from Turner.

continued below
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