What block does my 98 Z3 have?

[Revac]

What block does my U.S. 98 Z3 M52B28 have? Build date 7/98, so its not in the Nickelsil range, but before the TU iron liner. Have heard some say Alusil, and some say the M52 never got that. The block cast # at the top is hard to see, but with a borescope I read something like 1738408. SN at the bottom is 28528953. As for the bolt on metal tab at the lower left rear, I dont have that, but instead have bolted there what looks like a knock sensor.
Thanks

 

[NZ00Z3]

Alusil. The Z3 has an aluminium block. Most other USA BMW's with an M52B28 have a cast iron block.

 

[Revac]

Update, I pulled the intake off to do the M50 swap, and got a clean look at the casting number, and I got it way wrong above. The number on my 7/98 2.8 block is 1432219, so its iron sleeves.

 

[Andyboy]

No such thing as an Alusil M52 block. Alusil was used to make the V12 and later V8 blocks. The alloy is silicon impregnated and the boring process reveals the tiny particles that the rings run on. Nikasil was a nickel silicon coating on the bores on the alloy block.

Nikasil blocks were replaced around 3/98 with steel liner blocks. Iron blocks were used on US market Z3 2.8, E36 328i and E39 528i until 9/98. A tiny number of early UK cars have the iron block.

Steel liner alloy blocks have a rusty metal tab under the starter held on with a 10 mm bolt or allen bolt. Nikasil ones just have a pear shaped casting lug.