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Thread: M73 Engine Swap

  1. #1
    Join Date
    May 2017
    Location
    Flowery Branch, Georgia
    Posts
    13
    My Cars
    69 Ferrari Replica w/M73

    M73 Engine Swap

    I own a Ferrari 365GTS4 (Daytona Spyder) replica, built on a 1977 Corvette chassis. I've had the car for many years now, and have gone to some length to make it as close to a real Ferrari as possible, but at the end of the day, it still sounded like a Corvette. Last year, I wanted to fix that by installing a BMW V12 (ala Richard454). I think I read every post he made about his project on this forum and others (he is a prolific writer!), and then decided to try it myself. As it turns out, Richard lives close to me in Atlanta, and was kind enough to share his experience with me during a couple of visits to my shop. So last summer, I got an M73 out of a '98 750IL and started to work. I won't go into too much detail about what I had to do to get it to fit into the Corvette chassis, as Richard has already documented what is necessary to change a front-sump engine to a rear-sump, and I simply followed his lead.

    What I did want to share on this forum are some lesson-learned concerning getting the M73 to work in a different chassis, with a different engine management system. All the research I did beforehand seemed to indicate that the M73 (and the M70 before it) were inherently reliable engines, mechanically. Most of the issues I read about were related to the complexities associated with BMW's use of two DMEs, and the EML used to control two electronic throttles, so I opted to again follow Richard's lead and abandon the factory electronics and go with Megasquirt's MS3Pro. I have to say at this point that I couldn't be happier with that decision. I've worked with several aftermarket ECUs, and the MS3Pro is as good as anything I've used before. I specifically chose that unit because it supports fully sequential fuel injection on a V12, but as a bonus it was also one of the least expensive units available.
    As my main goal was to get the engine running and reliable, I opted to use the engine in as close to “stock” form as possible, only making changes that were required to get it to fit into the chassis, or to enhance reliability. As a result, no changed were made to the long block (other than to remove the oil pump). One thing I did notice when removing the pump was that on two different engines, the bolts holding the pump to the main bearing caps were loose. On the first engine I tried, the pump had actually loosened up so much that the pump cocked and snapped the chain. That engine obviously had bearing failure, so I got a second one. While the pump and chain were still intact on the second engine, those same bolts were loose, so failure was imminent. It would definitely be something I would check out if considering a swap using one of these engines.
    As the MegaSquirt is not able to control electronic throttles, I opted to remove them and replace them with a pair of throttles from an M30. They are slightly larger (67mm vs. 57mm) which is a bonus, and they will bolt onto the stock V12 manifolds by slightly elongating the bolt holes in the throttle bodies. If going this route, I would highly recommend staying with the progressive linkage used on those throttle bodies. On the first set I installed, I rigged up a simple cable linkage directly to the lever mounted on the throttle shaft. This engine has so much low-end torque that it was difficult to release the clutch from a dead stop without chirping the tires. I ended up re-installing the progressive linkage that came on the throttle bodies originally, which helped immensely. I guess the BMW engineers knew what they were doing!
    The end result is a very powerful setup that is exactly what I was looking for: 350+ horsepower without complicated systems like turbochargers, superchargers, or Vanos. I am a big proponent of those early V12s for that reason, and would be happy to respond to anyone who has questions about fitting one into their car. Here’s a couple of photos of the finished project:



  2. #2
    Join Date
    Apr 2012
    Location
    Stuttgart, Germany
    Posts
    440
    My Cars
    1997 M3 / 5.3
    Wow!

  3. #3
    Join Date
    Oct 2011
    Location
    Texas
    Posts
    42
    My Cars
    '04 Porsche CTT
    That's awesome!

  4. #4
    Join Date
    May 2017
    Location
    Flowery Branch, Georgia
    Posts
    13
    My Cars
    69 Ferrari Replica w/M73
    Thanks, guys. I read a lot about this engine before I decided to make the swap...some good, some not, but nothing I read would lead you to believe that it is an any way a performance engine. I mostly wanted to share my experience because I have found that it is a very responsive engine, in keeping with the image of the car I installed it in. The car was originally built with a Chevy 427, and was extremely quick. With this new engine and transmission, honestly, it seems every bit as quick. I was pleasantly surprised.

  5. #5
    Join Date
    Dec 2007
    Location
    Atlanta, GA
    Posts
    918
    My Cars
    M-Z3,535i, 320,Vette
    Hey CY-

    Turned out GREAT!!!


    Glad I could help!!! I'll be up your way in a week or two and will check it out.

    Richard

  6. #6
    Join Date
    Mar 2004
    Location
    Tyler, Tx
    Posts
    6,773
    My Cars
    '01 740i Sp, '07 335i
    Nice project - that is the same kit that was used on the Miami Vice cars, only one was an actual Ferrari....they went thru several during filming the series.
    http://i293.photobucket.com/albums/mm71/krallopian/darthSigTest2_zpsn6zkw5id.jpg[/URL][URL="http://www.facebook.com/pages/DFW7-Dallas-Fort-Worth-BMW-7-Series-Club/300942239566"]DFW7 on Facebook/URL]
    "The Last Great e38" 2001 i Sport - Born'd on date 1/01 Cosmos/Grey - 32.8K miles - 2 1/2 " Custom Exhaust, Center “X”over , Modified OEM rear bumper, M5 style trunk spoiler, M6 OEM wheels, M3 Steering wheel with working paddle shift & CF trim, Bi-Xenon upgrade, 13mm Rear sway bar added, SS brake lines and bronze bushings, Cross drilled rotors and painted calipers, Akebono pads, Zionsville aluminum radiator & exp. tank with electric fan, Sprint Booster, BluTooth conversion, MKIV Nav., Custom wood cupholder, DUDMD Tune, Orien V2.5 LED Angel Eyes, Evans waterless. Recently added grey faced //M5 Cluster - all gauges functioning. Changed the grey carpet to black and topped off with GG Bailey front/rear mats[/SIZE]

  7. #7
    Join Date
    Jun 2018
    Location
    Algérie
    Posts
    1
    My Cars
    Bmw e46
    Grand salut et total respect mon frere tres bon travail je suis entrain de faire presque le meme travail mais je suis coincé pas d'information. j'ai un m73 tu b54 de 750il e38 avec ces 4 ecu.je veux l'installer dans un e36 j'ai lu ton projet et j'espère que vous m'aider.tres grand salut de ma part merci mon frere.

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