Catching back up on what's happened with this car, which is random progress. I'm using my at-home desk time to finish the spec-out phase and get some major decisions made and re-start momentum.
In November I bought Alex Buchka's C30 front seats from his white 242 after he upgraded to some very nice black Recaro LS seats. The C30 seats are much firmer than 240 stockers but still quite comfy, and they do have a bit of bolstering to them. This material has some grip to it as well, it's nice. They are 100% manual which is fine with me. They have the C30 slider mechanism and are bolted to the floor with a version of Doug's brackets. The tilt forward feature is redundant in this car but doesn't hurt anything.
I'm pretty happy with the way they look in the early 240 interior. The door cards and carpet are brown, so the gray doesn't match, but doesn't clash either. If I keep these long term I'm sure I'll want to re-cover them along with the back seat in some kind of coordinating fashion.
Engine & trans fit-up and mounts are on hold for a bit as I figure out my front suspension and crossmember, since that's all interrelated. After talking with Eric O (Poik) and Dave Coleman about a particular unorthodox idea, I'm pursuing it full speed ahead now. That is converting the entire front end to an E36 setup. Crossmember, lower control arms, spindles, hubs, brakes, struts, steering rack will all be E36 M3 spec.
Racing a V8-swapped E36 in Lemons for the past 4 years has gotten me super familiar with these parts, their shortcomings, and how to set everything up for longevity and great performance. The lower control arm has a balljoint mount to the subframe where the 240 stock design has a bushing - this helps tremendously with steering feel as all of your lateral cornering loads are translated through metal all the way to the steering column. From the tire the load path is through the wheel, bearings, spindle, outer balljoint, inner ball joint, subframe, and steering rack. No rubber bushings anywhere in that stackup.
The wheel bearings are quite a bit bigger than 240 spec as are the brake rotors. Any E36 M3 brake upgrade, strut insert, or coilover should now be a candidate. I may stick with the stock M3 single piston calipers. By mounting them on bronze instead of rubber bushings, brake wear is incredible on our Lemons car. The caliper and pads stay straight and true vs the rotor and endurance spec pads last for 4 or 5 races on our car...that's like at least 4,000 to 5,000 miles of hard use, braking at the limit most of the time. Rotors last almost indefinitely now.
I started out with a test fit of the E36 front crossmember, strut, lower control arm, hub, etc. on one side. I think it's going to work. The crossmember width is within about 1/4" of the 240 crossmember, and the vertical height is about the same too. It attaches with 4 bolts into the frame rail members just like the 240, but the bolt holes are closer together and the crossmember sits at an angle in the E36. I think all of this is solvable though, but I may need to drop the back of the subframe down to correct geometry. I need to get the engine back in so I can finalize the position of everything.
Then I have a bunch of mounts / brackets to design & build.
- Engine mounts to frame rails
- E36 crossmember adaptation mods so it bolts into the body
- E36 strut top adapter to 240 towers
- E36 lower control arm rear bushing adapter / mount to the 3 bolt holes in the 240 where the bushing carrier bolts in
- Trans crossmember
Here's the E36 crossmember in place
Strut and spindle mocked up
The strut and spring I'm using for mockup is from a 325i, not M3. Comparison back to the stock '75 240 parts:
If you look at the relative positions of different points, the E36 spindle is up higher and further forward vs outer balljoint position. That effectively will act as a drop spindle and it builds in some caster. The spindle bolts onto the strut in a way that allows shimming between the two parts for static negative camber. I will see if I can get away with stock style upper strut mounts using BMW bearings and rubber, for a nice quiet ride. I'll avoid solid camber plates if possible for this car.
For now I'm working on making the final brake component decisions including master cylinder and booster, after which I'll finalize the crossmember position, then move on to the lower control arm rear mount adapter and upper strut adapter.