M50nv stroker build. Question about rotating assembly combo.

[aplinweiss_is]

I stumbled onto a free M54b25tu. It sat outside awhile with the valve cover off but I'm thinking the rotating assembly may be salvageable. A R3v member has a S50 crank for sale in the classifieds very fair priced. I googled around and couldn't find anyone that had the combo I'm thinking of using. My plan would be.

M50nv block
S50 crank
M54 pistons and rods

Is this not a reasonable option? Or am I missing something?

Thanks guys

[blink977]

Impossible combo. with the s50 crank 91mm stroke you will be out of deck by 70mm. I think you are getting what this means ;) I'm even not shure if s50 crank will fit M50 engine block, let anyone else answer this, but if yes than: S50 crank 135mm rod from M52b25 or M54B30, and M54b30 piston will take you to 1.18mm deck height, 3026cc displacement and 11.5:1 compression ratio depending on head gasket thickness. you choose.

[328ijunkie]

^What? No.

Only variable im unsure of is the pistons/rods. I know the B30 pistons/rods drop right in perfectly but unsure what the bore/stroke is on the B25

[aplinweiss_is]

^What? No.

Only variable im unsure of is the pistons/rods. I know the B30 pistons/rods drop right in perfectly but unsure what the bore/stroke is on the B25

From what I have found the M54b25 shares the 84mm bore.

The b25 has a 75mm stroke. B30 has 89.6mm stroke. I think.

It appears they share the same 135mm connecting rods.

The pistons I wonder about. The part numbers are not the same on real oem.
But they are both 84mm bore.

[yazansoft]

the us s50 crank 85.5 stroke,
s50 crank + m54piston + rod = the piston under deck about 4 mm in the TDC = low compression engine not efficient and bad assembly.

you can build high compression engine using:
s50 crank
135 mm rod "B28 OR B30 OR B25NV"
m52b28 piston
you get 2.85L engine but high compression around 11.5.

or u can use:
all m54 Assembly out of M54B30 you get 3.0L engine with stock 10.2 compression
the m54 crank is the same crank in s52 the two share 89.6 stroke.

[aplinweiss_is]

Ok, question then.

What if I use 140mm rods. Which by your statement would soak up the 4mm under deck and put me 1mm over deck.

Edited /\ the NV has 135mm rods, vanos 140mm rod

I'm guessing milling a millimeter off the piston top would not be a good idea.

Just grabbing at straws I guess to take advantage of the free motor and a cheap S50 crank.
Most people are proud of their M54b30 cranks. Like $500. I'm not complaining, I understand
The costs of a build, just trying to take advantage of some inexpensive parts.

[lennon]

i'm not going to do the math right now or tell you that combo will work, but milling 1mm off the top of the piston is fine. of course i would check the thickness first... but i've seen people remove more than 1mm from a BMW piston top.

[blink977]

Ok, question then.

What if I use 140mm rods. Which by your statement would soak up the 4mm under deck and put me 1mm over deck.

Edited /\ the NV has 135mm rods, vanos 140mm rod

I'm guessing milling a millimeter off the piston top would not be a good idea.

Just grabbing at straws I guess to take advantage of the free motor and a cheap S50 crank.
Most people are proud of their M54b30 cranks. Like $500. I'm not complaining, I understand
The costs of a build, just trying to take advantage of some inexpensive parts.

S50B30 - 85.5mm stroke, S50B32 - 91mm!
also mention: US M3 engine - S52B30 and S52B32.S50 is euro M3 engine and it is completely different!
you should have started this thread with explanation of which crank you are going to use, cause euro 3.2 M3 crank (S50) has 91mm stroke, US 3.2 M3 crank (S52) - 89.6, same then M54B30. M3 3.0 liter crank both US and euro are 85.5mm stroke.
Here the little table of M50 family engine parameters, I hope this helps:

M50B25 non-vanos engine:
Bore - 84mm
Stroke - 75mm
Rod - 135mm
Piston compression height - 38.2mm

M50B25TU vanos engine:
Bore - 84mm
Stroke - 75mm
Rod - 140mm
Piston compression height - 32.55mm

M52B25 - same then B25TU, but euros uses alloy block

M52B28
Bore - 84mm
Stroke - 84mm(forged crank)
Rod - 135mm (forged)
Piston comp.height - 31.82mm

M54B30 all engines are bi-vanos
Bore - 84mm
Stroke - 89.6mm(forged)
Rod - 135mm
Piston comp. height - 28.32mm

S50B30
Bore - 86mm
Stroke - 85.8mm
piston compression height - 31.6

S50B32
Bore - 86.4
Stroke - 91mm
Piston comp. height - 31mm

S52B30
Bore - 86mm
Stroke - ?
Piston compression height - 32.8mm

S52B32
Bore - 86.4mm
Stroke - 89.6mm
Piston comp height - 31mm

you can figure desired rotating combo by dividing stroke by 2+rod length+piston compression height-block height. I also found that there is block height difference between vanos and bi-vanos engine blocks, vanos are 210mm bi-vanos 211.

[devon.818]

all the motors use the same crank!
s50/s52/s54//m52/m54

why? idk, but you can even see that on realoem they are interchangeable.

[blink977]

all the motors use the same crank!
s50/s52/s54//m52/m54

why? idk, but you can even see that on realoem they are interchangeable.

yes, they are interchangeable but at the same way, are different by stroke

[aplinweiss_is]

Seems it all comes back to the tried and true combo.

S50 crank, 135mm rod, M50 vanos piston. Or complete M54b30 rotating assembly.

[trackjunkie21]

m54 assembly is drop in no hassle job. I plan on doing this sometime in the future.

[Hans Gruber]

You really dont need the s50 crank. The s52/m54 crank are the same.
Stroker build here:

http://forums.bimmerforums.com/forum/showthread.php?t=1715145

[e30polak]

all the motors use the same crank!
s50/s52/s54//m52/m54

why? idk, but you can even see that on realoem they are interchangeable.

The s54 crank is NOT the same as the other engines listed. While it may share the 3.2L displacement of an s52, it's harmonics are noticeably different, which is why it's able to rev so high.

[328ijunkie]

Bore and stroke on the S54 are completely different than the S52. And the only cranks you listed that are the same are the M54 and S52. All the others are different.