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Thread: E30 M42 to M44 Swap - Questions & Noob Build Thread

  1. #1
    Join Date
    Aug 2013
    Location
    NE Florida
    Posts
    5
    My Cars
    1990 E30 325i (sold)

    E30 M42 to M44 Swap - Questions & Noob Build Thread

    I'm creating this thread to document my M42 to M44 Conversion. It would also be great if people can chime in with recommendations, top tips, and other helpful advice. My wrenching experience is limited to oil changes,brake replacements and an AC overhaul. With that said, I already own the Bentley manual, and am willing to invest the time to do research. My first E30 was a '90 325i sedan w/H&R Springs, Bilsteins, LSD, and sport seats. It was my daily for ~4 years until I hit a deer. At 280k miles it still drove like new, and I regret not spending the time to fix it.

    Fast-forward ~10 years and I now own this non-running 1991 318i. The prior owner, a college student, advertised it as having a bad motor (doh!). He said the car overheated (broken temp gauge). He limped it home, but it sounded terrible. A mechanic friend of his said the engine was "toast" but didn't provide any details. It had a very clean body, newly wrapped sport seat interior, clean plastic bumpers, and the price was right. I figured worst-case would be an engine replacement...but a head gasket replacement was more likely.

    After having it towed home I went to work with the basics. Fresh oil and new plugs. When removing the plugs, the #3 spark plug cap was loose and the plug was also loose. I assumed the mechanic who the PO had look at it had left the cap off. Once I put in new plugs and the cap wouldn't go back on, I took a closer look and found that the cap of the spark plug had wound itself off and was stuck the boot/coil. 20180623_124213.jpg


    I was going to do a compression test, but was having a hard time determining what the Bentley manual meant by "unplugging the ignition at the firewall." The bentley manual isn't much help. They reference 4cyl and 6 cyl engines...but they're based on the M10, not the M42. I'd probably be better off with the E36 Manual. Wow, now that I'm thinking about it...I'll track one down for sure. Anyhow, I decided to skip the compression test and see if it would start...and it did. It actually sounded really healthy. The exhaust sounded like crap when you revved the engine, but there's no cat or resonator and it looked like there may be a few cracks where it was welded together.

    Diagnosing the coolant temp sensor (the one that feeds the gauge on the dash) was pretty simple. It was a pain to access without removing the airbox...but if you unplug the wire from the sensor, jump a wire from the sensor to the block, if the wiring is fine the temp gauge will jump. If it doesn't...you have a problem with the gauge cluster or wire. If it does move, the issue is your sensor. Once I replaced the sensor and verified the temp gauge was working I took a slow spin around my neighborhood. The car seemed Good. I also replaced the ground wire to the battery, since the connector had cracked.

    The next day I tried my first road test. After 10 miles it started sounding bad and missing. I turned around to limp home and it went "bang." In my rearview I saw pieces of debris bouncing down the road. I coasted to a stop and found a window in the engine. Here's a picture of a rod(?) poking through the driver-side engine support. Turns out, I did not win the lottery. The engine was in-fact toast.
    Last edited by etimm; 07-05-2018 at 01:27 PM. Reason: Add Pictures

  2. #2
    Join Date
    Aug 2013
    Location
    NE Florida
    Posts
    5
    My Cars
    1990 E30 325i (sold)
    The goal of this project was to compete in the Grassroots Motorsports Challange $2018, so budget is a definite concern. While the logical thing to do would be go with an M20B25 or a 24V, the time and cost of acquiring new ECU, drive shaft, and having to change wiring is probably above my skill level. After checking online, I found an M42 ~3 hours away, a cheap M44 of unknown origin nearby, and a free M44 ~3 hours away. The drawback of the free M44 is that the cams have been removed and need to be reinstalled. I have the Pelican Parts 101 projects book, and have read up some on the technique. It makes me a little nervous, but probably worth the risk.

    After comparing the engines on RealOEM, this looks doable. I've seen plenty of threads on this swap, but none seem to definitive. There's a wide range of opinions, but not too much feedback or details from people who have actually done the swap. I'm hoping to create this thread to identify and clarify any pain-points.

    I need to swap intake and oil pan from M42 to the M44 engine, maintaing the M42 ECU and wiring. I'll need to switch the drive belts from the M42, since the M44 uses a serpentine belt (not exactly how to do this until I have the engines side-by-side). The coolant lines appear pretty different, so I may try to find a complete hose set for each engine with the goal of replacing most/all of the hoses.

    The M44 only has one temp sensor, I guess I need to splice the wires from my M42 harness together? Could the same sensor feed both the ECU/DME and he dash?
    Are there any other difference I need to be aware of?

    So far I've removed the following
    Radiator & hoses
    Airbox
    Intake
    Fuids

    I need to remove
    Alternator
    AC compressor
    Belts
    Engine

    Question:
    Is it easier to remove the engine with the transmission or without?
    How difficult is it to separate the engine/transmission while it's in the car?
    If I leave the transmission in, do I still disconnect the drive shaft/guibo?
    If you leave the transmission in the car, do you just pull the engine forward, or do you use a jack the move the transmission away from the engine first?

    - - - Updated - - -

    Attachment 633191Attachment 633192
    Last edited by etimm; 07-05-2018 at 01:30 PM. Reason: additional details

  3. #3
    Join Date
    Aug 2013
    Location
    NE Florida
    Posts
    5
    My Cars
    1990 E30 325i (sold)
    For the record, in case other people attempting the same swap find this thread: Swapping the E30 M42 to an early E36 M42 is simple if you swap your e30 oil pan, intake and accessories. Swapping E30 M42 to E36 M44 is not at all simple. It's been done buy guys on the M42/M44 facebook group, and it requires the M44 wiring loom and a long list of parts. Based on this, I'm definitely going to stay with an M42. If I wanted to do something more challenging, I'd either to M20B25 or a newer 24V engine.

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