m20 flywheel

[e30sky]

ok guys well i am currently in the process of doing my m10 to m20 swap. these are my options m20b20, m20b25 or the m20b27 out of a 325e and also a e28. questions is are the fly wheels off of any m20 engine interchangeable on any of the engines i mentioned? because i have access to these engines but they were all auto. got all the basic parts but no flywheel. ummm most likely i'll be going m20b25 or the m20b27. so my question is mainly for those two engines. if i buy a used flywheel just for the time off a m20b25 engine can that bolt up to the m20b27?

[Hooffenstein HD]

Some one will surely correct me if I'm wrong but from memory:

They should be interchangeable, although different weights and different ring gears/starter motor depending on early, or late model M20.

Just have to match starter motor to flywheel.

[e30sky]

thanks for ur input

Some one will surely correct me if I'm wrong but from memory:

They should be interchangeable, although different weights and different ring gears/starter motor depending on early, or late model M20.

Just have to match starter motor to flywheel.

ummmm most likely the cars the m20's are out of will be early models. think up to 87 . i will have to double check and make sure tho.

[CW325]

An m20b27 will require a flywheel with tabs on it for the crank sensor. Also some mid year models had a dual-mass flywheel (my 86 had one) but this can be swapped out for a single mass as long as it has the tabs on it.

[TurboJake]

Depends on your DME and wiring harness. If you run the B25, you'll want a single mass flywheel and the Crank sensor will be on the front of the engine (DME Most often 173) . If you run a B27 with the B27 (DME most likely 027), you'll need to run the B27 Dual mass with the crank triggers on the flywheel. The sensors bolt into the transmission bellhousing (Which also means you need to use a B27 transmission, as the B25 one won't have the castings)

You can sometimes get lucky and find a single mass with the sensor triggers. Not sure how plentiful they are in the southern hemisphere.

[e30sky]

thank you

An m20b27 will require a flywheel with tabs on it for the crank sensor. Also some mid year models had a dual-mass flywheel (my 86 had one) but this can be swapped out for a single mass as long as it has the tabs on it.

i will have to go check and make sure what year is the m20b27 and then see what i need to make it possible

[e30sky]

thanks alot

Depends on your DME and wiring harness. If you run the B25, you'll want a single mass flywheel and the Crank sensor will be on the front of the engine (DME Most often 173) . If you run a B27 with the B27 (DME most likely 027), you'll need to run the B27 Dual mass with the crank triggers on the flywheel. The sensors bolt into the transmission bellhousing (Which also means you need to use a B27 transmission, as the B25 one won't have the castings)

You can sometimes get lucky and find a single mass with the sensor triggers. Not sure how plentiful they are in the southern hemisphere.

well the m20b27 are around here in Guyana, but mostly auto. so yeah finding a manual tranny for that engine will be tuff lol, there is alot of m20b25 with auto or manual set up. i guess if i dont get one then my only and best choice is the m20b25. u think u can get a picture of the m20b27 flywheel with the crank triggers u talking about?

[Madhatter]

also need to match the right transmission too, as they won't all have provisions for the flywheel sensors if that is the way you go.

The sensors are just two sensors side by side on the belhousing of the gearbox. One is a speed sensor and the other is a reference sensor to trigger the coil. If you look where the gearbox (transmission) bolts to the engine, you will either see two sensors coming out of it, or none.

Just start with a 325i complete, everything from motor to gearbox and you won't have to worry about the sensors and flywheel. If it's too hard/costly to find a 325i motor complete, what I would probably do is get EVERYTHING from the 320i, the motor, gearbox, all the ignition components, loom and ECU. This is basically a 325i as far as running components go. They use a similar ecu, the same loom, coil, cap, rotor and leads, everything right down to the O2 sensor and air flow meter. The difference is obviously in the size of the motor, but the throttle body is also slightly smaller and they run a different fuel pressure reg (2.5 bar), but otherwise it's the same.

Then just swap out the 2L bottom end for the 2.7L one from an eta, using the 320i head and all the electrics, swap the fuel reg for a 325i (3 bar) one, and you'll be virtually setup with a stroker conversion.

[CW325]

b27 flywheel tab

[e30sky]

wow.......thanks for the idea

also need to match the right transmission too, as they won't all have provisions for the flywheel sensors if that is the way you go.

The sensors are just two sensors side by side on the belhousing of the gearbox. One is a speed sensor and the other is a reference sensor to trigger the coil. If you look where the gearbox (transmission) bolts to the engine, you will either see two sensors coming out of it, or none.

Just start with a 325i complete, everything from motor to gearbox and you won't have to worry about the sensors and flywheel. If it's too hard/costly to find a 325i motor complete, what I would probably do is get EVERYTHING from the 320i, the motor, gearbox, all the ignition components, loom and ECU. This is basically a 325i as far as running components go. They use a similar ecu, the same loom, coil, cap, rotor and leads, everything right down to the O2 sensor and air flow meter. The difference is obviously in the size of the motor, but the throttle body is also slightly smaller and they run a different fuel pressure reg (2.5 bar), but otherwise it's the same.

Then just swap out the 2L bottom end for the 2.7L one from an eta, using the 320i head and all the electrics, swap the fuel reg for a 325i (3 bar) one, and you'll be virtually setup with a stroker conversion.

hey thanks alot for all the details. i will see what comes around because i am starting the engine swap after the holidays, i will need help from my friend on the swap and he will be available after the holidays because he got a lot of work to do at his workshop.
has anyone done this before? the 320i head with 2.7l bottom end if so what was the results?

thanks guys you are really helpful

[e30sky]

thanks for the pic

b27 flywheel tab

now i know what to look for lol