S50 Block Vs M50 Block

[e46s54dr]

I have a complete S50 engine that I plan on rebuilding. When I tore her down I noticed cylinder scoring in a single cylinder which will require an overbore.

Im wondering if the S50 block and the M50 block are exactly the same other than the obvious bore size. I know the S50 head and the M50 head share the same casting but have different cam, valve springs, and retainers. So Im wondering if the two blocks share the same casting from the factory early in its life and take separate paths when it comes to the machining. Im sure this topic has been brought up tons of time, but does anyone have a definite answer?

Also, Ive been reading that the earlier m50 non vanos engines have stronger casting and can be bored out more safely than the newer ones? Can anyone please confirm and/or elaborate this further for me?

Thanks in advance.

[Wanganstyle]

I have a complete S50 engine that I plan on rebuilding. When I tore her down I noticed cylinder scoring in a single cylinder which will require an overbore.

Im wondering if the S50 block and the M50 block are exactly the same other than the obvious bore size. I know the S50 head and the M50 head share the same casting but have different cam, valve springs, and retainers. So Im wondering if the two blocks share the same casting from the factory early in its life and take separate paths when it comes to the machining. Im sure this topic has been brought up tons of time, but does anyone have a definite answer?

Also, Ive been reading that the earlier m50 non vanos engines have stronger casting and can be bored out more safely than the newer ones? Can anyone please confirm and/or elaborate this further for me?

Thanks in advance.

same block and head casing, nonvanos castings are not much different than vanos. I actually installed Vanos on a M50 non vanos head and then installed it in my 97 M3 S52 in place of the original S52 head. All you will be doing is having the bore fit to S50 piston size, you could even go with S52 crank and pistons (and 86.4 bore) if you wanted to get to 3200cc instead of being at 3000cc. OR you could get to 3000cc without bore at all with the stock 2.5L bore; just add S52/m54b30 crank and pistons and rods and you are good.


did the damaged cylinder have a dead piston too?

[e46s54dr]

same block and head casing, nonvanos castings are not much different than vanos. I actually installed Vanos on a M50 non vanos head and then installed it in my 97 M3 S52 in place of the original S52 head. All you will be doing is having the bore fit to S50 piston size, you could even go with S52 crank and pistons (and 86.4 bore) if you wanted to get to 3200cc instead of being at 3000cc. OR you could get to 3000cc without bore at all with the stock 2.5L bore; just add S52/m54b30 crank and pistons and rods and you are good.


did the damaged cylinder have a dead piston too?

Thanks alot, that is very informative and answered all my questions.

[Myster-E]

Don't forget to run S50 or S52 oil squirters