Baseline
The car, as it actually is
The car's as-delivered condition, September 2026, and the source of truth for everything else on this page.
Established by a full inspection, test drive, and service at a San Mateo, CA specialist shop, 13 September 2026. Shop verdict: safe, sorted, and it drives wonderfully.
Inspection score
17 green4 yellow0 red21 items checked
At a glance
- Car
- 1971 BMW 3.0CS (E9), silver, flared CSL-homage build. Chassis rust-free; custom fabrication throughout is well executed.
- Engine
- BMW S38B36, 3.6L, from an E34 M5. Confirmed. Runs strong, with minor oil weeps only.
- Transmission
- Getrag G280 5-speed from the same M5 donor. Confirmed. First gear slightly noisy.
- Brakes
- E24/E28 hydroboost system, fitted to clear the S38 plenum, on the original CS calipers with custom stainless lines. Accumulator just replaced and holding pressure. Pedal safe but still soft, a hydroboost trait. Wants a more aggressive pad.
- Suspension
- Custom: yellow lowering springs front and rear, good shocks and struts, E28 M5 front sway bar. Rear bushings aging.
- Wheels & tires
- Authentic Alpina 17×8.5 front and 17×9.5 rear, on roughly 5mm front and 15 to 18mm rear spacers. Pirelli P Zero Nero 225/45 and 255/40-17, dated 2017/18: replace for age.
- Body
- Zender fiberglass box flares. Front air-dam lip needs a proper remount (temporarily zip-tied). Battery relocated to the trunk; spare well replaced with a box housing the M5 muffler.
- Electrical
- Charging correctly. Turn-signal fuse problem fixed: the wrong plastic fuses were melting, replaced with ceramic.
- Fluids
- All fresh as of September 2026: engine, transmission, differential, coolant, brake, and clutch.
Detailed baseline
Drivetrain, confirmed
- Engine: S38B36 3.6L inline-six from an E34 M5.
- Transmission: Getrag G280 5-speed from the same M5. Mounts were dated around 1989; the right one had collapsed and was replaced with 034Motorsport rubber mounts.
- Driveshaft: the flex disc (guibo) was tearing and was replaced with a Meyle HD unit.
- Differential: limited-slip; fluid serviced, exact ratio still to be confirmed.
- Exhaust: E34 M5 headers, a modified catless mid-section, and a resonated rear with the M5 muffler. The trunk floor was modified and a box built to fit the muffler. Catless is fine: the car is pre-1976 and California smog-exempt.
- Shifter: the rear carrier bushing was broken and was machined and rebuilt with a custom bushing; the cup, knuckle, and seal were replaced.
Brakes
An E24/E28 hydroboost system was adapted to clear the S38 intake plenum, running the original 3.0CS calipers and custom stainless lines with banjo fittings. The failing pressure accumulator, the cause of the soft pedal and weak assist, was replaced with an ATE unit and the system now holds pressure. The pedal is safe and working but still slightly soft, which is characteristic of hydroboost. Pads and rotors have plenty of life. The shop's recommended first improvement is a more aggressive pad compound; replacing the booster or master may or may not firm the pedal further and is optional.
Suspension
A custom performance setup: yellow lowering springs front and rear, replacement front shocks and rear struts in good shape, an E28 M5 front sway bar with Audi end links, and a rear sway bar. The car drives wonderfully. Flagged as aging: the rear trailing-arm bushings and rear sway-bar bushings, both recommended for replacement. Front control-arm and tension-rod bushings are fine, with a polyurethane upgrade as an option later; subframe bushings were already replaced. This is not the Raab-KW setup under consideration elsewhere on this page. It is a good existing spring-and-shock setup, so any coilover move is a decision to replace something good, not an upgrade from stock.
Wheels and tires
Authentic Alpina Classic 17×8.5 ET12 front (P/N 3611638, KBA 41262) and 17×9.5 ET24 rear (P/N 3611637, later 3611637T, KBA 41406), wheel set P/N 3611669, 5×120 bolt pattern, run on roughly 5mm front and 15 to 18mm rear spacers, giving an effective offset of about ET7 front and ET6 to 9 rear. Tires are Pirelli P Zero Nero 225/45-17 front and 255/40-17 rear, date-coded 2017/18 and due for replacement on age. No spare. The Alpina center-cap locks came without a key; they were picked off without damage and replacement keys are being made.
Body and chassis
The chassis is rust-free and the fabrication throughout is well executed. Zender fiberglass box flares. The front air-dam lip needs a proper repair and remount; it is temporarily zip-tied. The battery is relocated to the trunk, and the spare-tire well was removed and replaced with a fabricated box housing the M5 muffler. Paint, panels, glass, and seals are all good.
Electrical and interior
Charging correctly. The turn-signal fuse kept blowing; the root cause was the wrong plastic fuses melting and adding heat where ceramic ones belong. A ceramic torpedo fuse was fitted and the wiring confirmed good. Inside: Recaro seats, comfortable and well upholstered; gauges, vents, and windows all work; no radio.
Work completed, September 2026
Full fluid service: engine oil (with an oil analysis), transmission, differential, coolant flush, and brake and clutch fluid. Repairs: brake pressure accumulator, driveshaft guibo, right transmission mount, shifter carrier bushing, a fuel-pump O-ring that had been causing a fuel smell in the trunk, and the turn-signal fuse.
Source: full inspection, test drive, and service, San Mateo, CA specialist shop. Inspected 13 Sept 2026.
