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BMW 2002 M42 Swap How to

Build021 1976 BMW 2002 M42 49

We LOVE the M42 in an BMW 02.  Jake did the first one on his personal car back in 2007.  Sense then we have completed multiple of this same swap in house and have helped hundreds do the swap at home on their own.  This page is meant to answer a lot of the questions about the swap and give you more information to do it yourself. We sell mounts and other parts to help you accomplish this build on your own or we can do it in house.

We hope this walk though helps.  If you have any questions along the way feel free to contact us.

It is best to use as many parts from a BMW E30 M42 car rather than the E36 cars due to fitment with the intake manifold and oil pan.

Required Parts from E30

  • Complete engine with intake manifold and oil pan
  • Transmission 
  • All engine wiring 
  • 175 DME (engine computer) 
  • Chassis side c101 (if car is being parted, This is the round connector where the engine harness plugs into the chassis harness. It is located on the firewall of the e30 Make you you get 6-10” wire past the connect so you can tie into it.) 
  • Driveshaft 
  • Radiator (e30 m42 radiator only works on early cars without modification) 
  • e30 intank fuel pump and sending unit (wiring pigtails, again if car is being parted) 
  • Transmission shifter linkage 
  • Battery Cable and associated brackets, etc (The battery needs to be moved to the trunk) 

Mount information My mounts use the stock 2002 mounts (rubber or any version of poly). The trans mount uses the e30 rubber mounts and is bolted to the floor of the 2002. The best way to do this is get the engine in and on the engine mounts. Bolt the trans mount to the transmission and raise the trans and mount up so that the mount is touching the floor of the car.  Drill through the body and run some bolts through from the top.

Transmission Adjustments

The g240 from the E30 will fit into an e30 just as the g245 from an e21 fits other than a couple adjustments.  First of all the ears at the top of the transmission must be cut off to clear the tunnel.  Second the lower ribs at the front of the trans need to be shaved to clear the center steering track rod.

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Transmission before modification

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After modification

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Clearance for track rod, this should be cut back further than this pic.

Engine Bay Prep

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Once you pull the m10 it is a good idea to get a few things out of the way before putting the m42 in. With the engine out there is a lot more space so do it all now. First…clean the bay. Working in a clean engine bay is so much nicer than dealing with dirt and grease. You need to remove the battery tray from the front and relocate the battery to the trunk. On the early 02s the tray just unbolts but on the older cars you need to cut it out. Now is also a very good time to make the hole for battery cable and engine wiring to the DME (engine computer). I normally use a hole saw around 2”.   When drilling the hole make sure there is nothing on the other side you might drill through. It is also a good time to track down all the 2002 wires, coolant, oil pressure, starter signal, tach, switched 12v, etc  (refer to the wiring section below for more information)

Installing Engine

Remove the upper and lower intake manifold (it helps a lot)
● You must remove the steering track arm, or at least drop it down while putting the engine in.
● Hang the engine from only the front ring (located at the front of the head)
● Lift the engine as high as you can and have a helper lift the trans up and over the nose of the 02
● Start to lower the engine some, when the oil pan is almost going to hit the front of the 02 you will
need to twist the m42 so the oil pan is towards the drivers side.
● By doing this the head will clear the firewall and the oil pan will clear up front.
● While the engine is twisted lower the m42 some more.
● Once the engine clears the firewall and the front of the 02 you can let the engine twist back to
normal.
● Continue to lower the engine and use a jack at the back to level out the engine.
● Just go slow and the mounts will line up.
● To get the trans mount on, I bolt it to trans, jack the trans up so the mount touches the body of the car, drill some holes and use bolts from above with some large fender washers.

Shifter Install

There are a couple ways you can do this. It all depends on what you have on hand.  You can bolt the shifter carrier from a 2002 directly to the shell or modify the trans a bit more to use a early e30 sheet metal carrier as clay did.  Here is some info on that process.

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Drill and tap the bosses on the back of the trans, m10 x 1.5mm

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Cut 12-15mm off the platform and drill new mounting holes

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Bolted up with stock shifter carrier mounts and e30 318 rubber mount

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Installed in the car

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Shorten shifter rod to 8.25" center to center.

Driveshaft

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Angle iron bolted to the old mount to extend out the CSB. 7.5" hole to hole.

The stock BMW E30 M42 Driveshaft will fit perfectly in a 2002 other than the Center support bearing mount needs to be relocated.  You can make new mounts or use our method. Some have said this method doesn’t work but we have it working in many many cars all over the world with tons of miles on them.

Fuel System

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Just some info for feed and return at the rail.

Use the e30 intank fuel pump which also has a return fitting.

Throttle Cable

An aftermarket Lokar throttle cable works best here.  We use the 36″ version with part LOK-TC1000U36.  A little bracket down off the transmission to mount the bottom and then some stock BMW bits up at the throttle body.

You will NOT use the Lokar end up at the throttle.  Use the following BMW parts either bought new or cut the ends off an old throttle cable.

  • 13 54 1 288 013 – plastic throttle clip 
  • 35 41 1 152 372 – metal bar
Then use a cable crimp to secure it.

Cooling system

The M42 E30 radiator will fit without any issue in an early 02 (non big bumpers).  If you have a big bumper car you can fit the M42 radiator if you remove the added frame rails that mount the big bumpers.  If you do not want to remove those parts a volvo 240 radiator and external coolant tank will work.

Here is the Hose information 

  • Heater inlet hose that fits – D86063
  • Heater outlet – use the stock hose connector to the stock M42 outlet
  • Upper radiator use if using M42 radiator – C71663
  • Upper radiator hose if using volvo 240 radiator – E71994
  • Lower radiator hose if using M42 radiator – D71314
  • Lower radiator hose if using volvo 240 radiator – D71314
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Heater hose feed and return

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M42 E30 Radiator in early car

Build021 1976 BMW 2002 M42 49

Volvo 240 Radiator in Late car

Gauges

One downside to the M42 swap is that the g240 tranmission does not have a mechincal speedometer drive.  This isn’t THAT big of deal and there are a few options to handle it.  The lowest cost (which we will show below) is to use a electronic VDO speedo and sensor on the driveshaft.  Next you can use a speedo drive box to run the stock speedo and finally you can get custom gauges.

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2002 coolant temp senor in M42

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Speedo from behind

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Speedo from the front

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Speedo Speed Sensor

Wiring

In any swap it seems like people are most worried about the wiring. The wiring part on the m42 is NOT hard at all. There are only 9 wires needed to be hooked up to make it all run. I normally try and get a chassis side c101 connector from an late e30 so the m42 just plugs in. I also normally use a relay to keep the 02 power separated from the m42. I normally trigger the relay with the switched 12v that used to go to the coil connection. When the key is in run/start there is 12v to coil side of the relay and switches power from the battery source to the m42 c101 connector.  Anything not shown in the table below can be removed from the c101.  The info below is from the E30 wiring.  You CAN use the E36 wiring but there will be some sensors that do not work with the e30 intake manifold.  If you would like to use E36 wiring send us an email and we can get you the wiring information.  NOTE:  If you wire your car up and it doesn’t shut off the issue is with the alternator back feeding power through the excite wire.  The fix is to install a diode with the line facing TOWARDS the engine wiring.  

C101 connector face

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C101 PinConnection On 2002Function
1D+ at voltage regulatorAlternator excite connection
4not needed as you will use 02 wirecoolant temp
5wire from stock 2002 oil pressureoil pressure dummy light
612v in run/hot - power off relaym42 DME power
712v in run/hot - power off relay Coil Power
9connects to tach adapterTach Signal
12Ground side of 12v lightCheck engine light
1312v to fuel pump in,15amp fuseFuel Pump
18wire that was connected to starterStarter solenoid signal
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