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Common M20 Swap


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Hi everyone how's it going , I have a question for the m20 swap gurus .. I have a chance to get a m20 with trans and harnes out of a 87 325is, question is there any difference in the few years they made m20 is this year an ideal for a swap, maybe I should look for a newer m20 (out of the 90s) also I will be doing all the work myself , what will it take to install the motor far as where to get mounts for it and any other things I might need .. Just trying to get a good visual about everything I need before I jump into this .. Thanx everyone for your help

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Search M20 as well as M20 mounts in the search box in the upper right.


Google also helped me a lot with the beginning questions of the swap. Search M20 2002, M20 2002 Mounts. Look for the topics that pop up off of this forum.


As far as I know, an M20B25 (Any M20 from a 325i) is the same across the years. I may be wrong because I know the early/eta cars had Motronic 1.1 as opposed to the M20B25's that had Motronic 1.3.


If you want to purchase a set of mount you need to get in contact with whoever is selling them at the time. I know Manimal has made sets in the past, I got my set from him. Sin City BMW also sells them.


One thing I will say is I wouldn't say this swap is common. It's been done time and time again in the past but I wouldn't say it's a "bolt in" or "plug and play" engine swap. Be prepared and do your research to know what you're getting into!


Good luck!

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  • 3 weeks later...

Not all M20B25s are Motronic 1.3

1984-1987 325e were Motronic 1.0. This is the older setup with dual reference sensors in the bell housing, a cold start injector ect. ect. Much different than what the M20B25s have.

1987-1988  M20B25s had Motronic 1.1. This is the more "modern" set up with the single crank position sensor on the front, no cold start injector and the wiring/fuel set up under the hood is essentially the same as the later 1.3. In fact all you need to do for 1.3 conversion on the 1987-88 M20B25 is simply unplug and swap the DME from a later car.

1989-1991 M20B25 were Motronic 1.3. The main difference between this and the earlier 325i 1.1 is the DME. It has a removable chip which a lot of guys like because it lets you tune your E30. Motronic 1.3 is said to have typically smoother idle characteristics than 1.1, but the management is very similar. The plumbing in the cooling system also changes a bit and the water pump picks up from a different side (although the pumps are interchangeable since pretty much all M20B25 blocks are the same).

If it were me, I would get the engine and trans you have a line on, and simply find a 173DME from a 1989 and newer car.

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