The M30 engine was BMW's Big Six engine. It was the older, bigger brother to the Baby Six M20 engine fitted to 320i and 325i E30 models, and offers much bigger displacement and superior torque. Aside from the increased bulk, the M30 is a relatively simple engine to work on, and powered performance E30 models such as the Alpina.

This engine swap guide will help you fitting one of these coal-burning power stations into your E30.

Overview

While the M30 is a bulky old engine, it fits easily into an E30. If using the preferred base vehicle of a 325i, then the majority of existing Drivetrain components can be reused, with only the M30 engine and gearbox itself needing to be sourced. For smaller four-cylinder cars,

Remember, as with all engine swaps, it is important to make sure your Brakes and Suspension are up to the task of the increased power you will have.

Engine

While the M30 engine was available in a range of capacities, there's little point doing the swap if you're not going to use the biggest lump available, which is the 3.5-litre M30B35. These are best sourced from either an E32 or E34, 535i/735i, from around 1988 onwards. These later engines had bigger valves and better management, but also had lower compression compared to the earlier E28 engines and in return gives slightly less power. Skimming the head will increase compression and therefore power.

The standard E34/32 is 211bhp with 220 lbft. A 1mm head skim will give 220bhp with 238 lbft, comparable to the earlier engines.

While it's perfectly possible to fit the earlier engine, the coolant system will require more work which will involve blanking a pipe at the back of the head. It also necessitates swapping the sump, therefore increasing the number of parts required.

For the purpose of this guide, we will presume you are using an E32/E34 engine.

Parts List

As the M30 is an engine contemporary to the E30, the vast majority of components needed for the swap are BMW original parts that will just bolt on. Only one part needs to be custom made, and these are the engine mounts.

M30 Custom engine mounts

M30 engine & gearbox
Custom engine mounts
E30 M20 rubber mounts
E30 325i exhaust
E30 M20 radiator in good condition (preferred choice is E28 535i rad)
E30 325i gear linkages
E30 325i manual prop
E30 325i gearbox flange
E30 M20 matrix hose (or E28 T piece)
E34 throttle cable
Electric fan

This means that if you are starting with a 325i car, you only need a fan and a throttle cable to complete the swap.

This list does not include any performance upgrades such as a larger bore exhaust or bigger radiator, which can be added later on.

Custom mounts

Left side engine mount

You'll need custom mounts to get the M30 perfectly in place. You can have a go at making your own but you must get the engine perfect in the bay; the M30 is a big engine, and a few millimetres out of place will have it knocking against the bulkhead or smashing into the radiator. First of all it needs to be dead centre in the bay, then sitting at the right angle, then sat at the right height so it doesn't hit the cross-member, while at the same time low enough for you to shut the bonnet.

Much simpler is to buy a set from leeparkes, contactable through the Zone.

Right side engine mount

Between the engine mounts and the subframe, you can use standard M20 rubber mounts or any equivalent 50mm thick. One solution is to use Land Rover V8 mounts with a spacer to raise them up to 50mm; they are both strong and cheap. Other alternatives include uprated M20 ones from Burton Motorsport.

The custom mounts featured here have three positions.

I'd recommend using those that place the engine furthest back (position 3), although you may have clearance issues with the bulkhead in this position. If you do you can massage the bulkhead with a mallet just where the head sits, but don't bash too much as the brake linkage sits behind it.

If you use the furthest forward position, you'll have virtually no room for a radiator, as well as worse weight distribution.

This is position 3

Clearance to E28 535i radiator in position 3

Drivetrain

Gearbox

All M30 manual gearboxes will fit a late engine, not all M30 gearboxes fit earlier engines.

Clutch/Flywheel

If you are using the M30 gearbox you can use the standard dual mass flywheel and matching clutch or use an E28 M30 (or any M30 of the same era) flywheel which is single mass and much lighter. E28 535i = 10KG E28 525i = 7.5KG You can use 'any' single mass M30 240mm friction plate but must use a 3.5 pressure plate to handle the power. Aftermarket single mass flywheels are available which can use the dual mass clutch, BBB do them To round up E28 flywheels are lighter than E34 ones, so go for one of these if you can! You'll need the clutch to match (the E34 cluch won't work with an E28 fly for example) - I'd certainly recommend a new clutch while it's out & easy to change... The M30 gearbox bolts to the shell using standard E30 gearbox crossmember and standard gearbox mounts. An E30 325i gear linkage is needed to make the gear lever stick up in the right place... M20 or M30 clutch slave cylinder can be used.

M10 gearbox...............

Prop

There are four options available to finish off the drivetrain:

E30 M3: This has the correct flange to bolt to the E30 diff & M30 box.
E36 328i: with centre bearing mod.
Custom prop: can be had for around £100
Gearbox flange swap: you can swap the flange on the back of an M30 box for one from a M20 325i. Note it must be 325i as for some reason the 320i is different. Then a M20 325i manual prop can be used.

The most popular choice is last, as it's easily available and can cope with the torque.

Loom

Using the M30 engine loom, some minor modifications are needed.

Temp sensor - the brown temperature sensor on the M30 block will need swapping for an E30 M20 item.

Facelift wiring mods (these apply to those with a facelift shell) - the engine will run without doing them, but for everything to function correctly (rev counter etc), the following are needed;

You need to swap pins in the M30 loom, or cut wires. Pin 3 (black and white) and pin 8 (black and purple).

To get the electric windows and sunroof to work with the doors shut and for the heater blower to work at all you need to connect the black and green wire from pin 15 on the E30 C101 to a suitable earth on the body (mine is on the bonnet roller guide)

Power distribution block - there is a power distribution block on the E32/34 loom, near the ECU, that needs a direct live feed to it.

Coil will need to be moved to the suspension tower so the wires reach, also it give more room for the airbox

There are a few details of the later C101 (25 pin) being used here

ECU

The standard [E32]/[E34] [ECU] should be used although [M20] ECU's will work with the M30 EPROM [Chip|chip] fitted inside.

The M30 loom will allow it to be fitted under the dash, but getting all of the connectors through the bulkhead is a PITA! The loom is also slightly short - you have to rotate the ECU 180 degrees to allow it to bolt in place.

Cooling

You'll need an E32/E34 top hose, with the built-in T-piece to the heater matrix. This T-piece goes to the bottom connection on your heater matrix. You need another T-piece to go in the pipe from the thermostat housing to the header tank (from an [E28]; BMW part number # 11 53 1 272 866). You can then connect from here to the top connection on your heater matrix.

Or use a mixture of M20/M30 hoses to make the T piece up, front half M30, rear half with it already having the T to take off to the header.

Header tank

If you've got a pre-facelift shell, you'll need to move your header tank - the stock location is in the way of the air intake. A facelift m20 header tank sits nicely on the nearside wing - you'll need to extend the level sensor wiring round to it. It can obviously stay where it is if you're starting with a facelift m20 shell, It is possible to use the M30 one and fix to the bulkhead but there is really no need as standard E30 works fine.

Radiator

You can use a standard E30 radiator - a new 325i rad will do the job but a M30 is a big engine in a small E30 engine bay and heat is an issue so a bigger radiator is preferable. An E28 m535i radiator is loads bigger than an E30 rad and fits perfectly. There are even unused holes in the shell that you can bolt it up to.

If using the E28 rad you will need an E28 bottom hose to reach the lower bottom stub or extend the original E34 one like this.

An E34 535i radiator can also be used but it must be non aircon type, aircon rads wont fit between the chassis rails. To mount the E34 radiator you can use the standard 325 bottom plastic 'cup' mount on the right hand side and another right hand side one on the left hand side, riveted to the body as it doesn't clip in quite perfectly. The radiator sits in this like it was made to measure!

The crankshaft pulley will be very close to the radiator whichever you use. Unless you're keeping the M30 aircon setup (& I very much doubt you are!), you can chop the air conditioning belt drive part of the pulley off, simply by running an angle grinder down the middle of the 'V', it removes the spot welds and the two halves fall away.

Fan

You won't fit a viscous in there so electric is the way forward. Learn more about fitting an electric fan.

Airbox

Standard M30 airbox with E34 wash bottle.

The E32/E34 airbox fits just fine in the E30 bay. It's got a built in heat shield too - a distinct bonus as it sits above the exhaust manifold... Aftermarket options are out there and if you go down that route make sure its shielded from the heat.

After market filter with air tight heat shield and E36 washer bottle.

To fit the standard airbox you will need to move the washer bottle. An alternative bottle can be fitted to the E30 airbox mount or the standard location - an E34 non-intensive bottle is a nice fit. Also, a 324td washer bottle (p/n 6166 1385 280) is ideal.

Throttle cable

The M20 throttle cable is too short. Use one from an E32/E34 - about £15 brand new from BMW or off your donor.

PAS

Use the M30 PAS pump with M20 hoses.

Exhaust

The issue here is clearance to the steering coupling with none E34 manifolds. An E28 manifold is apparently a nightmare in this respect, & the E32 item (with a flexible coupling in the front section) would also have needed lots of work. The E34 item fits perfect and clears the standard rack.

E34 downpipes can be used, usually cut off before the front box. Some minor custom work will be needed to get from here to the back of the car.

An easy fix is to cut the M30 downpipes just after the gearbox then cut an M20 325i system slightly longer and slide it into the M30 downpipes. M30 pipes ID 50mm, M20 ID 46mm so its a perfect fit with no welding required.

Chopped E34 downpipes.

Chopped 325 downpipes.

325 downpipes clamped into the E34 pipes.

Perfect choice is a system that is 50mm pipes straight through as BMW intended but a 325i system will do the job just fine.

Fitting an E36 rack

Apart from the obvious when fitting a quicker rack, i.e. spacers, different hoses etc.With an E36 rack the pinion is closer to the manifold so it needs cutting and moving closer to the block by circa 20mm. The rear manifold clears fine but its the long front manifold that needs modding. The route I went down was cut the flange off the manifold then put some new pipe in angled towards the engine.