M20b25 into a 91 318

[bimmerlover]

Like the subject says, I'm curious about this swap and how involved it might be.
I ask for a friend actually, not myself. But what we're looking at doing is taking an M20 from a 90 325i with 115k on it and dropping it into a 91 318i with a bad motor.
We've got the tranny and diff needed for the M20.. what other parts should be gathered? What problems should we expect to run into?

TIA

Rach

[ZiMMie]

Dont forger 325i calipers and suspension.

[James Crivellone]

Dont forger 325i calipers and suspension.

the 318's in 90/91/92 had all that stuff already

[Bryson]

bolts in w/ the exception of a few things. It's been years so I don't remember

[nefarious7907]

are you sure the suspensions are the same? It would seem logical that the extra weight (200-300lbs) would have some effect on the shocks and brakes. You might want to look in some catalogs and see if the part numbes are the same for all the shocks and stuff.

[Bryson]

they are the same, the springs are not
If you don't get a 1990+ motor there is a wire that you have to run to retain the function of ABS

[bimmerlover]

they are the same, the springs are not
If you don't get a 1990+ motor there is a wire that you have to run to retain the function of ABS

Thanks for your help.. good to know that the swap has been successfully pulled off and isn't too difficult.

Yeah, it is a 90 motor.. and ABS would be the least of my worries.

[moutraklas]

since i am interested in performing this conversion in my 318i cabrio, i d like to ask tha following:
I have an airbag. The donor car must have had an airbag too? I mean, the airbag depends on the basic electrical circuit that will be changed to the one of the 325 or not? It is similar to the matter with the ABS. Must the donor car have had ABS?
Thanks

[clutterbucker]

extra 200-300 lbs? I'm not sure about that. The m20 weighs only 258lbs (take off the AC and you're barely over 200) while the m42 weighs 220lbs. Basically no difference aside from a much more primative engine, the extra 30hp, and far worse gas mileage.

Not a good swap to bother with when the M50 (weighing in at 299lbs) is just a viable an option, in my opnion.

[Jarvis]

He means the whole car's weight.
318i/is ~2600-2650lbs vs. 325i/is ~2850 lbs.

The 318's engine, tranny and differential are all individually lighter than the 325's same components. The spring rates are different.

PS: The M20B25 doesn't get horrible gas mileage compared to an M42. I've gotten 31mpg travelling at 70-75mph with an M20 with no mods other than exhaust. And that was in a 2800lb 325is with a 180lb driver and ~200lbs worth of crap in the trunk and back seat.