Opel GT Forum banner

BMW M42 engine swap into Manta?

57K views 138 replies 37 participants last post by  cadence 
#1 ·
Has anyone looked into using a bmw M42 4 cylinder engine?

I am buying a parts car for body and interior panels for my 91 318is and it has a working, complete, m42 with getrag 240/5sp transmission. I know that the opel getrag will bolt in using parts from OGTS. i was wondering how different the mouting points and/or output shaft are for the bmw getrag 240. Its front sump so i will have to start measuring to see if the motor will even fit. but i thought i would put this out there first.

it makes 140hp/130ftlbs torque crank for that amount of power with a modern direct fire ignition and fuel injection for basically free. i think it would be a better candidate than dumping loads of money in the stock motor for comparable power.
 
#2 ·
I would think it would be a very tight fit. It's angled over as installed in a BMW, and as well it's quite a bit wider with the manifolds and twin cam head.

If you straightened up the block so it was upright, you'd have a few more issues...it would end up being significantly taller, the manifolds would have to be modified/reconfigured, and the oil pan and pickup would also have to be modified to avoid oil starvation.

I've built a few headers for these engines and they're not easy to work on!
 
#3 ·
Ha! This is a coincidence. My brother just sent me an ad from a guy in our little town who is selling an M42 engine and trans, and my brother was thinking about swapping it into the GT. On the plus side, M42s are light, and the intake and exhaust are on the same sides as the opel, but I haven't even seen it yet so I can't say whether it would fit or not. I think RallyBob raises some valid points, but any swap is going to have its challenges! The question is are you ready for this much of a challenge!?

Good luck if you decide to proceed!

jtb
 
#4 · (Edited)
On the plus side, M42s are light, and the intake and exhaust are on the same sides as the opel, but I haven't even seen it yet so I can't say whether it would fit or not.
jtb
The M42 (like most BMW engines) is a crossflow motor, with the exhaust manifold on the same side as the Opel's, but the intake is on the other side.

It is a pretty tall motor, even in a 3 series the engine had to be tilted. The intake runners sit very high. It would be an excellent motor for a GT, though, if you can make it fit.

Dieter
 

Attachments

#7 · (Edited)
#14 ·
Here is a picture of the self contained wiring harness. Power cable to battery from alt., ecu plug (long Skinny), and body plug (big Round). the body plug contains 15 wires more than half of which are for the instrument cluster, and diagnostics. I will need to wire in a couple grounds, start signal, switched power, constant power and fuel pump. The relays for starter, fuel pump, and ecu are already built in to the harness.

http://i123.photobucket.com/albums/o281/sidv66/DSCF0173.jpg

and just some random pictures of the motor
http://i123.photobucket.com/albums/o281/sidv66/DSCF0170.jpg

http://i123.photobucket.com/albums/o281/sidv66/DSCF0164.jpg

http://i123.photobucket.com/albums/o281/sidv66/DSCF0171.jpg
 
#15 ·
Looks Good.

Have done a few different engine swaps in my day, while keep the EFI from that same engine.

My only advice to you is to get a BMW Factory service manual for this car/engine with a good wiring diagram.

Don't get a Chiltons (or the alike) they generally will not answer the hard questions that you will run into, like... "What the @!?#% does this wire do",
or "Why won't the @!$@ engine run"

Been there,... Done that!!
 
#16 ·
progress is slow going. I am surprisingly busy this winter. I finally got around to removing the engine from the manta, and taking engine bay measurements. from the crossmember to the hood bmw = 20 1/2" manta = 20" much closer than i expected. the length of the transmissions and engines are almost identical. i was too tired to write anything down last night but i will get some good measurements and better pictures soon.

http://i123.photobucket.com/albums/o281/sidv66/Cars/img1263866002699.jpg
 
#17 ·
#18 ·
BMW driveshaft

My suggestion is to leave the front of the driveshaft as it is to bolt up to the BMW transmission and make up the rear to the right measurment with a u-joint to bolt up to the Opel torque tube/propeller shaft, unless you are going to change out the rear end for something else.
 
#21 ·
good to know, thank you, I had read something in the sr20 swap thread, and misinterpreted the reason for the spring. I will hopefully be dropping in the m42 this weekend to check clearances and mock up motor mounts. The transmission mount from the bmw will bolt in with some modification. the mount holes will need to be elongated slightly and grind some of the metal to allow it to fit between the lugs on the transmission tunnel.
 
#22 ·
I got the m42 dropped in.







the oil pan sits about 3.5" from the steering rack. Once i get it pushed back where i want it, it should still clear with an inch or so to spare. The header is pretty close to the frame rail but should fit fine once i get it tilted to the correct angle. I didn't have any help today so i couldn't get it all the way back and tilted all the way over, but tomorrow my dad will be helping me get it into position and get the trans mount bolted up. The height is going to be close. I hope again this will be resolved when it is tilted correctly and pushed back. The stock opel motor mounts will line up with the lugs on the block. I will just need to make some simple brackets. I might even be able to modify the stock Opel brackets to fit.
 
#25 ·
i bet that M motor is alot of fun in a manta. i need an intake setup like that.


i've got it tilted in there at the correct angle. I ended up having take the header off to get it in there. It is going to take some simple flat brackets to mount the transmission. the engine mounts should be pretty easy also. I was wondering if anyone has used a different steering rack successfully. the height is an issue, but i think that if i can move the steering rack down to the same height as the crossmember the hood will probably clear. here are some updated pictures with a real camera.









 
#27 ·
BMW question

A little off topic, but one of my neighbours has a '94 BMW 328i which has got (in his view) terminal frame rot....I know it's a 6 cylinder (M50?) with a 5 speed manual attached....that's about all I know at the moment...
Does anyone know of any 'showstoppers' for dropping this combo into a Manta?
 
#29 · (Edited)
A little off topic, but one of my neighbours has a '94 BMW 328i which has got (in his view) terminal frame rot....I know it's a 6 cylinder (M50?) with a 5 speed manual attached....that's about all I know at the moment...
Does anyone know of any 'showstoppers' for dropping this combo into a Manta?
its going to be long and tall. the m42 was the test bench for designing the m50/m52 so it has the same cylinder spacing and almost the same height. they weigh over 300lbs engine only. they are also front sump oil pans

http://i27.photobucket.com/albums/c155/JoM3/mantaAm3.jpg this loooks like an s50 m3 engine though which is basically the same size and shape in a 73 manta so it should fit.

I haven't had a chance to work on the car as my dad is going to be renting his house so i have been cleaning up the garage instead of working on the car. no worries though the garage the manta is in will still be available after the renters move in.
 
#28 ·
Good work dude!! If you take your time and stay motivated a have 100% confidence in your success!!
 
#30 ·
I know its been a while but now i have the manta moved into my own garage and have that garage cleaned out and organized to an extent that working on the manta can resume. i have finished the engine mounts and the engine is now supported by them. i have aquired a clutch actuator for the hydraulic slave cylinder. here are the pictures with the mostly finished motor mounts and with them bolted to the engine. i will be working on the transmission mounts next and then on to wiring and getting it running. after that i will measure for the drive shaft and send it off to be made. progress is progress no matter how small.









 
Top