M20 Interchange

[macksbbq]

Hi,

My girlfriend has a 1990 525i with the M20 engine and around 235,000 miles on the clock--she bought it at 218,000. The previous owner did not apparently take very good care of the car and the engine is showing signs of severe wear. She is on a budget right now as she has recently gone back to school, so we are considering buying a lower-mileage replacement M20 to drop in and get the BMW back on the road.

I am wondering if an M20 from a similar year-model 325 can be interchanged with the one in our e34? What years will easily interchange? If it's a matter of getting a gasket set and swapping the oil pan or other external accessories, I can handle that, but I'm mostly concerned with being able to drop in a long block that will work with the existing accessories, computer, and wiring. I've searched all over and haven't been able to find a definitive guide to the M20's nuances from model year to year and car to car.

[Dave M]

I'll try and keep your first post near the top. Someone else may have a better answer, but.............

Speaking from having swapped in an M50 block from an e36, I can't imagine you'll have any trouble with wiring/DME 'stuff'. I'm assuming the oil pan will have to be swapped over. One thing I had to fiddle with was the engine mount brackets. The block had various threaded holes used for different e-types. Of couse the e34 threads were rusted beyond use, so i tapped them out larger. Relatively easy fix.

Otherwise, I don't see why an M20 from an e30 shouldn't work.

Dave

[macksbbq]

Thanks for the reply. That sounds pretty straight forward. From what I've been able to find out, the 2.5l M20 was updated for the last time in 1987, so I'm hoping that means that any 1987 or newer M20 long block would be a drop in. It looks like the main (only?) difference was the switch to Motronic fuel injection. Do you have any idea if extra sensors were added to the block or head with this system? What about the cam profile--did BMW update their camshaft through the model years?

[E34-520iSE]

The dipstick is in a different place on the e30 M20 block. That's the only difference I have seen on the e30's I have broken up.

HTH,

Shaun M