Boosted Big Six: 1985 BMW 735i E23

The E23 was BMW’s first-generation 7-Series, sold from 1977–1986, and the 735i was the big-engine version most Americans saw near the end of the run. These cars have aged into a wonderfully angular combination of executive sedan with styling that looks good, safety that is acceptable, and reliable enough to be a daily driver. Today’s example is a U.S.-spec 735i used the 3.4-liter M30 “big six”, one of BMW’s great old engines: iron block, aluminum SOHC head, timing chain, lots of low-end torque and a reputation for very high mileage when cooling systems and valve adjustments are kept up. They didn’t come with giant turbos when new, but this one is boosted for extra fun. Find this 1985 BMW 735i offered for $4,500 in San Jose, CA via facemorket bavaribook.

From the seller:

1985 BMW series 7
$4,500
Listed 20 hours ago in San Jose, CA
About this vehicle
Driven 240,000 miles
Manual transmission
Exterior color: White · Interior color: Tan
Fuel type: Petrol
Good condition
Seller’s description
Title: 1985 BMW 735i (E23) Manual – Microsquirt / BBS / Turbo Ready – Needs Head – $4,500 OBO
Price: $4,500 OBO
San Jose.
Clean Title in Hand | Will need to be trailered
Up for sale is my 1985 BMW 735i (E23). The car has a ton of great conversion work done, but currently needs an M30 cylinder head.
The head gasket let go when the car was turbocharged. Upon teardown, the head was excessively warped and was discarded, so it will need a replacement cylinder head bolted up to be back on the road. The setup has been reverted to naturally aspirated, but everything is plumbed and ready for either NA driving or an easy re-turbo build.
Body, paint, and interior are all remarkably clean and tidy for a 40-year-old classic.
Drivetrain & Trans Swap
Manual Conversion: Swapped to a Getrag 240 manual gearbox.
Lightweight Flywheel Setup: Fitted with an M10 single-mass flywheel (~14–16 lbs vs. the stock dual-mass/heavy M30 unit at ~28–30 lbs) for significantly quicker rev response.
Clutch: Sachs Stage 2 clutch kit.
Driveline: Custom driveshaft built to match the manual swap.
Engine Management & Fuel
ECU: MicroSquirt standalone ECU (tuned via TunerStudio).
Ignition: Audi Coil-on-Plug (COP) conversion.
Fuel: BMW M52 “pink top” injectors (21.5 lb/hr).
Oil Pan: Sump is already tapped/plugged for a turbo oil return line.
Wheels & Suspension
Genuine BBS 16×8 wheels square all around.
Good tires with plenty of tread remaining.
Included / Tuning Notes
Tunes: Comes with a base map file for an HX35 turbo setup. The current NA setup was assembled right before parking, so the NA fuel/spark map will need dial-in/finishing in TunerStudio once the new head is on.
Turbo Rebuild Spares: If the buyer wants to take it back to forced induction, I can include a set of GM/LS truck coils and 440cc injectors.
Note: Turbocharged, this chassis is an absolute weapon, but as with any standalone/swapped build, local emissions/smog compliance will be the buyer’s responsibility.
The hard fabrication and conversion work is already done. Source an M30 head (comes with new gasket and head studs to suit NA build), plug the harness back together, dial in the tune, and you have an exceptionally cool, manual E23 cruiser.
Car does not run and must be trailered away. Priced to sell at $4,500 OBO. Serious inquiries only – cash in hand for title transfer.

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