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Thread: E21 M42 subframe mount specs?

  1. #1
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    E21 M42 subframe mount specs?

    Does anyone have specs on the mounts that are used to reinforce the E21 subframe? Based on images from the various swap threads, it looks like there isnt anything too specific, were they just designed with the subframe out and see what fits?

    Am I making this out to be more complicated that it should be? I wanted to start planning before I fill up my garage with 1 more engine

  2. #2
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    Quote Originally Posted by jaredmac11 View Post
    ....... specs on the mounts that are used to reinforce the E21 subframe?

    Based on images from the various swap threads.......just designed with the subframe out and see what fits
    sorry Jared, I was on the road the past few days....

    the subframe does not need to be reinforced, but you do need to make new engine mounts. there is two ways to do this;

    one is to make new mounting arms from the engine block to the exsisting subframe perches for the M10. personally I think this is the hardest and least direct route to take. there is a vendor that makes arms for this application, but I think they miss the mark by a long shot and I have told him as much. you could find the tread by doing a search.

    the second way is to use the factory mounting arms and make new subframe perches. I use the E30 units and a piece of small C channel cut and welded to the frame. there was a tread by Irish were we discussed this at length. the best way to do this is to hang the engine in place and make a cardboard perch, copy it to steel and weld it in place.

    - - - Updated - - -

    you want to do this with the subframe in place.

    - - - Updated - - -

    and here's the link https://www.bimmerforums.com/forum/s...ighlight=perch
    Tom D

    77 e21 - m42
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  3. #3
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    Thanks Tom, great thread.. I had missed this in my searches.

    To be honest its hard to make a lot of sense of it from here, I need to get the M10 out and start mocking stuff up. I have a feeling this will be the biggest struggle for me but I'll get it in.


    Despite using the E36 motor, I used a lot of E30 parts... oil pan, accessories, including mounting arms. The e36 arms are substantially larger.


    Also, for anyone followng... here's where I picked up the mount discussion from the thread Tom linked:
    https://www.bimmerforums.com/forum/s...1#post27148891

  4. #4
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    Does the stock e21 radiator work with the M42 swap or does it need to be changed? I want to do an M42 swap in the near future.

    I am considering getting the eBay e21 aluminum radiator, but I don't want it if I am unable to use it with the m42.

  5. #5
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    Why not use the m42 radiator as well?
    1999 Z3 Coupe 2.8L


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  6. #6
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    Does anyone have detailed measurements of the M42 engine mount perches I can use for the subframe? I am going to probably take the subframe to a shop and/or have someone else weld it for me. I do not trust my welding skills for something like this. The M42 swap may take place over my thanksgiving break instead of next summer.
    Last edited by Thecatmilton; 09-16-2017 at 02:50 AM.

  7. #7
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    I dont think anyone does, honestly. I could be mistaken. You are gonna have to fool around with cardboard cutouts to get something close.

    I've seen people use C channel but I liked how Tom did his-- you can still easily get a wrench in there to get to the mount bolt. I imagine you can use L-channel with some cutting/grinding down to fit. Good luck.

    https://www.bimmerforums.com/forum/s...3#post29792333
    Another reference:
    http://www.m42club.com/forum/index.p...3883#msg123883
    And another (carries on to Page 6):
    https://www.r3vlimited.com/board/sho...6&postcount=75

    I'm interested to know how they even got the engine mount bolts on those last 2....


    I was planning to be done by now but Harvey had its way with the house so the car is still sitting up on blocks where I left it before the storm.

  8. #8
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    Quote Originally Posted by jaredmac11 View Post
    I dont think anyone does, honestly. I could be mistaken. You are gonna have to fool around with cardboard cutouts to get something close.

    I've seen people use C channel but I liked how Tom did his-- you can still easily get a wrench in there to get to the mount bolt. I imagine you can use L-channel with some cutting/grinding down to fit. Good luck.

    https://www.bimmerforums.com/forum/s...3#post29792333
    Another reference:
    http://www.m42club.com/forum/index.p...3883#msg123883
    And another (carries on to Page 6):
    https://www.r3vlimited.com/board/sho...6&postcount=75

    I'm interested to know how they even got the engine mount bolts on those last 2....


    I was planning to be done by now but Harvey had its way with the house so the car is still sitting up on blocks where I left it before the storm.
    Did you have any flooding? I used to live out in sugarland.

  9. #9
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    Yea we got about 3-4" in the home. The good thing is I'm working on the home to make future clean up much easier. It's a pain to get water of any amount but I'm thankful it wasn't enough to make us lose all contents.

    My wife keeps begging us to move out to Sugarland..

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