Crank compatibility

[JAR]

I am not sure if this is possible or the wisest course of action, but would appreciate feedback.  My 528i engine is all original, but I have some nagging “seeping”.  The timing chain gaskets, rear main seal, and the cam rear cover.  Seems like it is time to re-seal the motor, or just live with the seeping.  To address these properly, am I looking at pulling the engine? I have a 633i complete engine crated in the garage, maybe a good time to swap motors?
What is involved in swapping the 633 crank over to the 528?  Is it worth it?

Thanks!
 



 

[Mike W.]

Nice looking E12!

You will need to pull either the engine or the tranny to address the rear main, the end of the crank goes thru it. The rear cam cover can be done in place, but it's very, very tight.

You could theoretically swap the crank, but you'd either need to bore out the 2.8 or get custom pistons made. 2.8s use a 86MM bore, 3.3s use a 89MM bore. However it's a M30 so you could also just swap engines. If the 3.3 is Motronic without a conventional distributor you will need an adapter nut for the cam which I believe is still available. Otherwise a different cam. There might be one or two other things, but minor.

However, M30s aren't the driest engines, I wouldn't be surprised if the 3.3 has at least some of the same leaks if you don't reseal it.

[JAR]

Thanks Mike.
 The E12 is a two owner car and just about to roll to 50k original miles.  I just try to upgrade things when I can, as they need to be addressed.  Figured the best way to seal the engine was to pull it.  I was just noticing differences in the blocks, the 3.3 has a raised section on the driver side that is very short and only has 1 freeze plug, but the 2.8 runs halfway down the block  with 2 freeze plugs.  Both are supposed to be 1980 model year blocks, just roused curiosity as to difference.  

Hope to contribute in a positive way to the knowledge base here!

Jamie
 

 

[Mike W.]

There's a thing, and I can't remember it now, about early 3.5s, the so called M90 engines which have a different cooling casting on the intake side of the block. But there's also some US spec 3.3s with heads having a M90 stamping on them, inside IIRC. On the intake side of the block is cast the possible displacement, yours should have 2.5/2.8, which relates to 86MM bore. 3.0/3.3 means 89MM bore. 3.5 is 3.5 only which is 92MM bore. Except early 3.5s were 93.4 bore. Just for shits and giggles I'd check out the side of your 633 engine and see what it says. I'd say there is a remote chance it's an early 3.5, AKA M90. Remote, don't bet your retirement on it. But worth checking out.

But your car! A 50K E12? I bought my first E12 in '92 I think it was. 197K on it. Cracked head, an oval bore, I rebuild it and 130K later at 327K it got rear ended and totaled. A long story, but it only lasted another 60K after that, I saw it dead in a parking lot with 385 on the odo years later.

BTW, there is also First Fives, a dedicated E12 website where I'm a moderator. Not a lot of traffic, but some. https://www.firstfives.org/phpBB-3.2.1/phpBB3/index.php

[JAR]

Thanks Mike,

I am pretty sure the 633 block has the 3.0/3.3 on the intake side.  Regardless, it is nice to have a complete engine to borrow parts from.  The 528, is my third E12.  I started with a 1975 530i, that was a real basket case, so I started collecting parts.  Heck I still have some early E12 parts that won’t work on the ‘80.  One day I’ll eBay the strays.  I am also on firstfives, but due to so little activity saw a suggestion to this sight, as it is more active and has a lot of info that is good for the E12 too.  So, here I am.

 Found a great place in Murry, Utah, that doesn’t just rebuild, they “restore” calipers.