can you m30b34 swap 633csi...

[babyflanders]

I was wondering if it is a direct swap for a m30b34 in a 633csi. I know the 633csi comes with the b32 which is less displacement than the b34 but it would still be a direct swap... right?

[Shipper]

Yes, with the usual changes. I swapped an S38B38 into my 633. Engine mounts may change. Ecu may change.

[Bert Poliakoff]

It should be a bolt in. Big difference will be in the engine wiring harness based on what injection system you use. Odds are you will use an 83-85 motor, just a guess, so as Shipper said, a different ecu and probably engine harness,

[DesktopDave]

Do you have more detailed info on the donor and the recipient? Like model, build date, model year, etc.?

It's a bolt-in swap if you're pulling a Motronic B32 (late '81-early '84) to swap in a Motronic B34 (late '84-early '87). If there are any differences between the late E32 and the B34 other than displacement, I've never noted them. They all look identical on the outside, but there are some variants like the B34 high-compression Euro motor.

[babyflanders]

The car is an 83

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I can just order oem ones off the internet though, right?

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What do you mean by the ecu "may" change. Is it possible to keep my stock ecu?

[DesktopDave]

That'll work. Your car is running the Motronic 1.0 ECU then (Bosch calls them DME, just to be difficult). Just pop the harness, fuel rail & accessories off the current motor & bolt them onto the B34. The Motronic 1.0 isn't especially particular, it'll easily adapt to the larger motor.

There's a lot of 'while you're in there stuff' I'd guess you're replacing before the swap, since it's so accessible with the motor out of the car. Little stuff like gaskets, seals, maybe a smoke test for vac leaks. Most gaskets are paper, and will have hardened up on older motors. Others are OK to get at after the swap, but that rear main seal and the two rear gaskets (the heater core output pipe and the 'duck' gasket) are difficult to change once it's swapped into the car.

If you don't mind me asking, is there anything wrong with the current engine? Personally, I like swapping motors, but your plans will involve a lot of work for only a little gain. There isn't much of a difference between the two US motors, similar HP and a few torques. The B34 is more resistant to pinging due to the lower compression ratio.

A lot of people swap in the later B35 instead, there are lots of threads here on that topic. That's best done with an E24 B35 engine harness, some B34 engine parts, pretty much everything from the donor car, along with some modified engine mounts and exhaust work.

[babyflanders]

Thanks this helped a lot. And the engine as of right now doesn't seem to have any problems just leaks coolant and needs a new oil filter, but the odometer broke at 200k so I'm planning to have to swap it soon.