1986 M20b25 into 1990 325ix

[rtkelly32]

Hi guys, I have a 1990 325ix with a blown motor. currently looking at a good deal on a 1986 m20b25 out of a 325ix. I’m seeing most of everything is adaptable onto the head and block, but wondering if there are any issues I’ll run into with the drivetrain and ecu.

[TobyB]

As long as it's not an eta and you change things such as sensors, oil pan and the thermostat housing, it ought to work just fine...
www.realoem.com has part numbers broken out, if you want to go through it carefully.

t

[litu]

That info what you are giving, it is bolt on job...When you have old engine out and you have "new" engine by side you can see what need to take your current engine to that "new" engine...
It looks like that your current engine is Motronic 1.3 ECU system and "new" engine is -86 so it should be Motronic 1 ECU system, so i would take from your current engine, water pump/belt pulley, harmonic balancer, crank shaft position sensor/holder, oil level sensor, engine wire harness.

[Northern]

Intermediate shaft/oil pump should be different/spin the other way. Oil pressure relief also likely different. Might need an extra hole drilled for oil pan (or plugged/ignored, I can't remember which way.

Not sure the best route for what to change over as far as the above.
I would run all the '90 ix electronics, I think there are ABS differences that may be tied into the ECU?

I haven't owned an ix in 10 years so I'm rusty.

[TobyB]

Intermediate shaft/oil pump should be different/spin the other way.

Do tell more. I've only dealt with the M10 1980 direction change- didn't have a clue that the M20 also changed...

t

[Northern]

From a few sources:

https://www.r3vlimited.com/board/forum/e30-technical-forums/325ix-technical-and-discussion/192173-e30-block-differences

the ix uses a different oil pump and intermediate shaft gear. you'll have to remove the oil pressure regulator from the RWD block. there's nowhere to put a dipstick for the ix.

best bet - remove the internals from your RWD block, put them in an ix block.

https://www.r3vlimited.com/board/forum/e30-technical-forums/325ix-technical-and-discussion/302030-325ix-stroker-help

For us ix people though the oil dipstick is in a different place, the oil pickup is at the back and not the front, and the intermediate shaft that drives the oil pump is geared different and spins backwards (WTF why? Can someone explain?) so realistically, the best option is to swap in 1988 SETA pistons, rods and the crank.

[litu]

But that dude who was post this topic has luck, when both engines are from e30 ix, current is with FL motronic 1.3 system and "new" is from PFL motronic 1

[digger]

Do tell more. I've only dealt with the M10 1980 direction change- didn't have a clue that the M20 also changed...

t

The intermediate shaft doesn't reverse but the oil pump and the shaft runs the opposite direction because the gear on the intermediate shaft is different.