M90 Engine Verification – Looking for a Second Opinion

Curious_G

Curious_G

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Hello All,

I’m buying the engine shown in the attached photos. After doing some research online and on this forum, I believe the engine is indeed an M90.

The block code is 1304239, I see the nice 3.5 imprint, and the date code is 2D79 (April 2, 1979), which seems promising.

It would be great to have another set of eyes confirm my findings. Thank you for the help!

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0EB4CEDA-540C-46CF-8930-24CA29B6B672.jpeg
923F4738-9B82-452A-BFDB-B50C98214926.jpeg

- Curious_G
 

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Hard for me to tell. However if it has the raised water passage on the left side of the block, it is. It also appears to have the oil cooler filter head which would tell me it's an M90 Also the fact that the car is a '79 with 3.5 on it should also point to the fact as long as the engine is original
 
Here is a pic of my M90 (pre-rebuild). You can clearly see the painted "L" on the water jacket. Mine is a 1980 car.My engine does not have the round silver valve that sits intjhe center of your picture. The one connected to a hose that goes to the cold start valve on the intake. That hose is covering up the place where the "L" would be.

I agree with Bert that if this is really a 1979 3.5 engine, then it is almost certainly an M90. However, it is also possible that it is a later engine that was fitted to the car. The oil filter and oil cooler hoses also look like what I would expect with an M90.

You will definitely find out once you pull the head. Have you done a leak down test on it? I'd do that if you can before you buy it, since that will also tell you what needs fixing. In my M90 the compression was poor in two cylinders and this turned out to be due to blow-by between the cylinders (a uniquely M90/M88/S38 issue because of the narrow cylinder spacing.

BMWEngine1.jpg
 
That's an M90. Early one. Has the ribs lower on the block that went away on the later blocks. Flat above the starter should have the chassis number of the car it came from. If it has the original head, its an early small port one.
 
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