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Engine Spec

Whilst aesthetically they look identical and to all intents and purposes they are, the common misconception is the Z1 and 3 Series E30 325i engines are interchangeable.

The Z1 is fitted with the North American derivative of the M20B25, the 4WD 325IX engine, also supplied to the LHD European market. All ancillary items are the same as the 325i, including power output and service schedules. However the Z1s more 'mid' engine positioning to achieve its famed 50/50 weight distribution, meant the sump had to be altered to clear the front axle, and oil pump supply lines lengthened.

It has been suggested the sump of a Z1 will fit the 325i, however whilst this may be the case, that does not take into account the oil pump and dip stick arrangement, as they are positioned at opposite ends, presumably they would be relocated and the original dip stick hole sealed up.

The Cylinder Head part numbers are shared across all 4 derivatives, Z1, US 325ix, EU 325ix and 325i - 11121707032.

The Block and Oil pump part numbers appear to be shared across the Z1, US 325ix, EU 325ix - 1111171480 and 11411706805. But not the 325i - 11111714834.

The Sump part numbers are shared across both US and EU 325ix - 1131706697. But not the Z1 nor 325i.

  • E30 4WD 325IX
  • M20B25
  • 2494cc
  • 6 Cylinder
  • SOHC 12v
  • Petrol
  • 170HP
  • 125kw@5800rpm
  • 163ft/LB@4300rpm
  • 22.4MPG
  • 5 Speed Manual (Getrag 260/5)
  • 1,250KG
  • 4.3ltr Oil

E30 325i and 325ix

Spot the difference, one is a Z1 and the other an E30 325i.

The Z1 is on the left, the dip stick is located to the rear of the engine bay.


Although gearing is similar to the 325i, the Gearbox is also unique to the Z1, because of the torque tube mounting on the rear, making them non-interchangeable.

However it 'may' be possible to fit a 325i gearbox if you swap over the rear casing, but this is unconfirmed. The Technical team at BMW HQ should be able to answer that, or Mobile Tradition.


5 speed manual Getrag 260/5

Gear…….Ratio…….1000…….2000…….3000………4000…….5000………6000 (RPM)

1 ………..3.83……..5………….10…………15…………20………..25………..30 (MPH)

2…………2.20……..9………….18…………26…………35………..43………..52 (MPH)

3…………1.40……..14………..27…………40…………55………..68…………81 (MPH)

4…………1.0……….19………..38…………57…………76………..95…………114 (MPH)

5………….0.81……..24……….47…………70…………94………..117……….141 (MPH)

Gearbox Oil

The BMW Handbook states “Mobil SHC 630” - SHC stands for Synthetic HydroCarbon. A good synthetic is recommended as most mineral oils are like treacle at low temperature, they can gel at about -5C, whereas most synthetics are fluid at very low temps.

Sticky 1st Gear

From cold, it is normal for the gears to feel very hard and sticky, wait a few minutes and allow the oil to warm up, DO NOT attempt to force it. Some owners have opted for Redline MTL oil to smooth out the problem, with slicker movement when cold.

Guibo / UJ

To change the Guibo, (aka Universal Joint or Hardydisk), remove the exhaust, Differential and supporting tube around the drive shaft, then separate the Gearbox from the Torque Tube to gain access to the drive shaft and subsequent joint inside.


The Diff is a large case 3:64. Any of the E30325 LSD will fit including the M3 with minimum effort providing you swap the faceplate, adding a new gasket and oil.

  • 3:64
  • 3:73
  • 3:91
  • 4:10


Caution!Danger of scalding! Unscrew cap on expansion tank only when engine is cold. Remove engine splash guard. Drain and catch coolant.

Disconnect top water hose. Disconnect venting pipe on the radiator.

Disconnect bottom water hose. Press engine oil cooler to the left and detach on the right side.

Detach engine oil cooler on the left side.Pipes remain connected

Pull out expansion rivets at top left and right.Pull out fan cowl from above.

Installation:Disengage retainers on left and right sides and at bottom center.

Press on radiator mounts at top left and right with a screwdriver. Pull out radiator carefully from above, pressing the spill pipe out of the clamps.

Installation: Insert mounting clamps on the radiator prior to installation. Make sure of correct seating on the bottom rubber mounts when lifting in the radiator.

Radiator Flush

  • Radiator Removed

If there is oil in the cooling circuit, the radiator and expansion tank must be flushed and cleaned with solvethane”


  1. Remove expansion tank in addition to radiator
  2. Pour in 2 liters of Solvethan
  3. Shake radiator and expansion tank thoroughly and drain Solvethane after oil has been dissolve
  4. Install the cleaned radiator and expansion tank again, and connect them on the cooling circuit
  5. Fill the entire cooling system with hot water and flush thoroughly to safely remove remainders of Solvethane, repeating this step several times as necessary
  6. Inspect the drained water for traces of oil and, if necessary, repeat step 5. Fill and bleed the cooling system after completion of the cleaning procedures

Note: Solvethane attacks rubber seals, rubber hose. Consequently it must not get into or remain in the cooling circult. Always conform with safety precautions for working with Solvethane (printed on containers).


Servicing the Z1 engine is well documented throughout the internet on various well established sites, it does not differ from the standard E30 325i and perhaps does not need further explanation. Following the OEM recommended service schedules, the M20B25 will run forever.

Tappet / Cambelt

To get a full instruction, look at the Haynes or Bentley manual for the E30 325.

There always is a slight amount of tappet clatter on the m20 engine - if you've managed to get rid of it, there probably isn't enough clearance.

The water pump and idle do not have to be changed with the cam belt, but they are not expensive items, and it makes sense to do them at the same time. The idler will look after the belt, and the water pump is underneath it, so by replacing it as preventative maintainance will save you time later.

It is also a good idea, whilst ferreting around the front of the engine to have a good look at all the hoses. Age will take a toll on these items regardless of mileage, so look out for swellings or soft spots, especially around the clips.

If you have been changing your coolant every two years from new, then the radiator shouldn't be silted up, but it wont do any harm to back flush it with a hose pipe whilst the system is drained. Make sure you use hi-spec coolant, not because the engine is difficult or highly stressed, but because as the car ages you want to do all you can to preserve radiators and block.

Spark Plugs

Take off spark plug connector. Tightening torque = 20 to 30 Nm (14.5 to 21.5 ft. lbs.), if working without Special Tool 12 1 172.


Disconnect battery ground lead (or positive connection point on the firewall).

Remove air cleaner with air flow sensor. Pull off plug. Loosen hose clamp. Lift out air cleaner with air flow sensor.

Note:Check rubber mounts (1 and 2).

Alternator: Take off protective cap. Disconnect leads on connections B + (term. 30) and D + (term. 61).

Unscrew top nut and take off bolt together with the tensioning wheel. Unscrew bottom nut and remove bolt (leads D + / B + disconnected).

Fuel Filter

Installing Clamp the fuel feed hose before and after the filter with Special Tools, unscrew screw (1). Loosen hose clamps (2 and 3).

Pull off fuel hoses. Take out filter.

Installation: Check direction of flow = arrow (4).


A number of Tuners released modified versions of the Z1, Alpina being the only officially recognised manufacturer to release the Z1 RLE, Roadster Limited Edition with their own unique Alpina serial number.

Alpina RLE

  • Engine: 2.7 ltr 200 BHP
  • Brakes: original
  • Suspension: 20mm lower
  • Wheels: 4 stud 8*17 Alpina Multispoke, 235 40 17 tyres and badge with production number
  • Rear axle Drive: 3.73
  • Exhaust: Alpina
  • Exterior: Alpina striping and badges
  • Interior: Alpina Steering wheel
  • Alpina Gear Knob
  • Alpina Badge with production number
  • Alpina Chassis Number


  • Engine: 2.5: 195 BHP, 2.7: 220 BHP, 3.0: 230 BHP, Turbo 245 BHP
  • Brakes: front 295-25
  • Suspension: 40mm lower
  • Wheels: 4 stud: 8 and 9* 16 with Tyres 225-50-16 front and 245-45-16 Rear
  • Extra Wide body kit
  • Wheels 9 and 10*17 with Tyres 245-40-17 front and 275-35-17 Rear
  • Rear axle Drive: Several
  • Exhaust: Hamann
  • Exterior: Wide body kit, rear spoiler, front spoiler and badges
  • Interior: Steering wheel
  • Shift Knob
  • Floor mats
  • Hamann Instruments
  • Aluminium pedals


  • Engine: 2.7 ltr 205 BHP
  • Brakes: front 295-25
  • Suspension: 25mm lower
  • Wheels: 4 stud: 7,5 and 8,5*17 with 235-45-17
  • Rear axle Drive: 4.27
  • Exhaust: Hartge
  • Exterior: Hartge badge and body stripes
  • Interior: Steering wheel and shift knob

AC Schnitzer

  • Engine: 2.7 ltr 200 BHP
  • Brakes: in combination with 5 stud conversion 280-25-17 front
  • Suspension: 25mm lower 4 stud and 5 stud
  • Wheels: 5 stud: 7,5*17 with 215-40 and 8,5*17 with 245-35, 4 stud: 8*16 with 225-45-16
  • Rear axle Drive: several
  • Exhaust: original
  • Exterior: Schnitzer badges
  • Interior: Steering wheel
  • Gear knob
  • Floormats
  • Aluminium pedals


  • Engine: 2.7 ltr 204 BHP, 2.8 210 BHP, 2.5 Turbo 220 BHP, 2.8 Turbo 250 BHP
  • Brakes: several aftermarket kits
  • Suspension: several aftermarket kits
  • Wheels: several aftermarket kits 4 or 5 stud
  • Rear axle Drive: several
  • Exhaust: 4pipe Lorenz stainless steel
  • Lorenz front spoiler and badges
  • Steering wheel
  • Shift knob
  • Floor mats


  • Engine: 3.0 ltr 210 BHP,
  • Brakes: original
  • Suspension: original
  • Wheels: original
  • Rear axle Drive: original
  • Exhaust: Wiesmann
  • Exterior: Hardtop
  • Steering wheel
  • Gear knob
  • Floor mats


  • Engine: several from 2,5 -3.0 ltr.
  • Brakes: several aftermarket kits
  • Suspension: several aftermarket kits
  • Wheels: several aftermarket kits 4 stud
  • Rear axle Drive: several
  • Exhaust: Schaffer
  • Exterior: Badges
  • Short shifter
  • Wind deflector
  • Steering wheel
  • Gear knob
  • Floor mats

Griffin Motorsport

  • Engine: 2.7 ltr 210BHP
  • Brakes: Original
  • Suspension: Original
  • Wheels: Original
  • Rear Axle Drive: Original
  • Exhaust: Griffin
  • Exterior: Badges
  • Interior: Right Hand Drive conversion

Birds Engineering

  • Engine: 2.7 ltr 210BHP
  • Brakes: Original
  • Suspension: Original
  • Wheels: Original
  • Rear Axle Drive: Original
  • Exhaust: Original
  • Exterior: Original
  • Interior: Right Hand Drive conversion


engine.txt · Last modified: 2014/04/17 15:08 by zadmin