E30 Project: Replacement for M40 engine...?

[Murt97]

So I have had my first E30 cabrio for 3 months now and i’m loving it, the only issue has been the engine...

While I actually don’t mind the M40’s limited performance, it’s leaking oil and I suspect camshaft damage as the revs won’t go over 5k RPM? The engine has 190k+ miles on it, so I think it’s time to explore the idea of an engine swap.

So it’s between M42 or M20b25? Performance is better than the M40 in both cases, so really it just depends if I can find a good deal on either engine and just roll with whatever I can get.

Which engine would you choose and why?

How do I go about finding said engines? I’ve seen a couple on facebook and one on ebay but not much luck anywhere else (I live near London).

I want to keep engine swap costs below £1000 as I hope to do most of the work alongside my father @ home on a tight budget. The goal is to get the car mechanically sound with either the M42 or M20b25 before I get it resprayed and rust repaired.

Any feed back would be very appreciated.

[rix313]

Cheapest option will be the M42 as your can use a lot of the M40 parts to fit it. I’m not too familiar with the diff ratio on a cabrio but the running gear can remain the same where as you’d need a gearbox and a diff for an M20b25 swap.

Something to consider though is the 318iS and the 325i both came with rear brake discs, 51mm front struts and bigger front brakes which your 318i does not have. As they say, safety is no accident!

[Murt97]

Cheapest option will be the M42 as your can use a lot of the M40 parts to fit it. I’m not too familiar with the diff ratio on a cabrio but the running gear can remain the same where as you’d need a gearbox and a diff for an M20b25 swap.

Something to consider though is the 318iS and the 325i both came with rear brake discs, 51mm front struts and bigger front brakes which your 318i does not have. As they say, safety is no accident!

I found a decent E36 m42 engine for £300, I’m definitely considering it.

My cabrio has rear disc brakes but I’m going to upgrade brakes allround anyway as they don’t have much bite.

[JungleGus]

If you're looking to fit to a budget and don't mind M40 performance, M42 seems like a stellar option in my eyes. If you wanted to build a stroker and get more power and sound nice down the line, M20 sure...but doesn't seem worth the box/driveshaft/exhaust etc. change.

I am not familiar with how swappable M40/2 is but I think it's pretty much plug and play, maybe a small amount of welding for the ignitor brackets. Give the cam cover and intake a lick of paint and change some of the basic gaskets and you should be in great shape for a long time

[Murt97]

If you're looking to fit to a budget and don't mind M40 performance, M42 seems like a stellar option in my eyes. If you wanted to build a stroker and get more power and sound nice down the line, M20 sure...but doesn't seem worth the box/driveshaft/exhaust etc. change.

I am not familiar with how swappable M40/2 is but I think it's pretty much plug and play, maybe a small amount of welding for the ignitor brackets. Give the cam cover and intake a lick of paint and change some of the basic gaskets and you should be in great shape for a long time

Yep, m42 sounds good.

I’m trying to figure out if a E36 M42 engine will fit an M40 Getrag 240 transmission that’s already in my car.

Any answers to this^^ would be very hepful!!

[JohnA]

I am currently doing the same thing, putting a m42 e36 in an 318i e30. all is out, engine gaskets, waterpump, thermostat clutch etc replaced. My m42 engine came from an automatic, but it will fit the getrag 240. the engine block is the same.

[boiliebasher]

I agreed with the general consensus that the M42 engine would be the cheaper and easier option

[Murt97]

I am currently doing the same thing, putting a m42 e36 in an 318i e30. all is out, engine gaskets, waterpump, thermostat clutch etc replaced. My m42 engine came from an automatic, but it will fit the getrag 240. the engine block is the same.

Is your getrag 240 from an m40 or m42? I’m guessing you’re using existing transmission from your 318i

[rix313]

Have you read the conversation sticky in the M40/42 section. All your questions will be answered

[JohnA]

@Murt97, yes it is the getrag 240 that came with my 318i m40

[Murt97]

@Murt97, yes it is the getrag 240 that came with my 318i m40

How’s your engine swap going??

[JohnA]

The engine is in, all is connected. and It fired up the first try, without any warning lights, so i guess the e36 loom mod did work. I found a pre '94 e36 ecu on ebay, to bypass the ews (my engine is a '95)

biggest problem was the ebay exhaust manifold , the tube going to cyl3 did not clear the engine support... so i had the choice of making a custom support, or putting in a new section of tubing. I did option 2 and put in a section of the e36 exhaust. it did work, but it was a #!@ welding between the other tubes ( i added a picture)

the air filter box needed to be placed forward to fit on the e36 intake, this needed a new bracket, but it is now squeezed betweed the radiator and the abs system... we'll see how this works.

the bracket for the ignition system was straightforward. I still need to clean up all the wiring, removing the surplus 36-automatic wires. also I forgot to replace the coolant temp sensor ( it needs the brown one ), so the intake manifold needs to come out again.

next week i will try to work out how to connect the exhaust manifold to the existing 318i cat, this will require a bit of trial and error, cutting and welding

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[martauto]

Nice work mate
Feels good when a plan comes together

Mart.

[JohnA]

passed the MOT today without any problems There is a rattle however around 3000 rpm. the cam sprockets teeth looked fine when the engine was out, and i replaced the tensioner. This could be the chain? although it only has 180k kms. I have another job ahead of me... to bad I was not aware ofthis when the engine was out of the car. This is the danger buying an engine already disasembled