M50tu Stroker Build Questions

[Johnsonmjm]

I have taken on the venture of building a M50tu with a M54 rotating assembly. I also have the car running on megasquirt, so the tuning aspect isn't an issue

My questions are what are necessary steps to make the M54 crankshaft fit, like the windage tray trimming and whatnot? (I already removed the reluctor wheel on the crankshaft since the M50 uses a crankshaft pulley reluctor wheel.)

What are the tolerances for the main and rod bearing clearances?

Should I upgrade to the 21lbs injectors or will the 17lbs be fine. (I read somewhere the S50 uses 17lbs injectors)

What is the final displacement? (I've heard 2.9L, 3.0L and 2.8L)

Thanks All
-Matt

[jmc1590]

Displacement? Which M54 are you using? Are you using all of the rotating assy, or just some parts?

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[gdavid]

Assuming you are using the M54b30 (or s52) crank, the displacement is 2,979 cc

Main Bearing Clearance: 0.0007- 0.0029
Connecting Rod Clearance: 0.0007-0.0029

Depending on your tune you could probably get away with #17 but for the amount of work you are doing, I assume you will want #21.

What are you doing for cams?

My stroker motor started with a m52b25 which is going into my 1996 328 so I will be using the m52b28 manifold, injectors and tune. I have a modified m52b30 intake cam in it.
I haven't installed the motor yet so any advice I have is only based on research so far but everything I have read lead me away from using the m54 oil control rings (bottom ring) which are an odd 2 piece design rather than the conventional 3 piece design. The M54's had a bad reputation for oil consumption and many believe that this 2 piece ring was to blame.

This can be solved by using the m52 or m50 oil control rings, note that the compression (top) ring for the m54 pistons is only 1.2mm tall versus the 1.5mm height of the m50 & M52 engines so you can't just order a regular set of M50/M52 rings, you need to custom order the rings to get get a set that has a 1.2 mm top ring, 1.5 mm middle ring and 2.0 mm 3 piece oil control ring. I bought a set of mahle off of ebay and just requested the configuration I wanted and it was no problem.

[M3blitkrieg]

Leave the ring on the crankshaft as it is actually a structural component of the crankshaft. If it's not there and specifically the bosses not holding a bolt, it creates a stress pinot that can snap. Had happened to at least a few support guys I've read online. I take it with salt, but at the same time it can't be a coincidence.
What I did for the splash shield was get another,, cut out the less deep wells and weld in the more deep wells from thenother splash shield. Cleared with no issues. To be honest, it's much safer to just let the machine shop make the calls. Get a shop that has experience with performance engines and they will probably make sure everything's done correctly. Other than that, just make sure clearances are right, cylinders are not out of round. And make sure you do NOT mix up the crank bearing caps. They go with the block. No cap=junk block.
Regular green top injectors are fine for a 3l. Even with m50 manifold, the 3.l cams, and other na mods. But if you feel like getting fancy or going fi, they say pinks or higher.
Also, I took the advise from the other guys on here and got the n54 exhaust studs. They thread in themselves, just the right height to make exhaust install pretty easy, even supersprint headers that are a pita.

[Johnsonmjm]

From what I understand though, is that the ring will end up hitting the block since the M50 uses an external crank sensor. So I ended up taking it off. My plan is to run m50tu cams (unless I find a set of m54 cams, or s50 cams for cheap). Only modification from the M50 is the rotating assembly itself. I will be using a m50 manifold (since that's what it came with, Thank god), green top injectors (until I find a set of pink tops for relatively cheap so I can run smaller ve table numbers, or maybe some 80 lbs siemen dekas for when I boost it at 6psi), and an intake and exhaust. Hopefully I'll be around 230bhp with the tune (Luckily running megasquirt, the stock m50tu is running on it at the moment due to plans of this build, and boost.)

Leave the ring on the crankshaft as it is actually a structural component of the crankshaft. If it's not there and specifically the bosses not holding a bolt, it creates a stress pinot that can snap. Had happened to at least a few support guys I've read online. I take it with salt, but at the same time it can't be a coincidence.
What I did for the splash shield was get another,, cut out the less deep wells and weld in the more deep wells from thenother splash shield. Cleared with no issues. To be honest, it's much safer to just let the machine shop make the calls. Get a shop that has experience with performance engines and they will probably make sure everything's done correctly. Other than that, just make sure clearances are right, cylinders are not out of round. And make sure you do NOT mix up the crank bearing caps. They go with the block. No cap=junk block.
Regular green top injectors are fine for a 3l. Even with m50 manifold, the 3.l cams, and other na mods. But if you feel like getting fancy or going fi, they say pinks or higher.
Also, I took the advise from the other guys on here and got the n54 exhaust studs. They thread in themselves, just the right height to make exhaust install pretty easy, even supersprint headers that are a pita.

- - - Updated - - -

I'm using a m50tub25 block, with a complete m54b30 rotating assembly. M50 manifold, stock m50tu cams, intake, exhaust, and green tops. I think I'm going to keep the rings as they are, I got a killer deal on an m54b30 that had less than 300 miles on it, the rod and main bearings still had the glaze on them from break in.

Number one piston ended up breaking, but I'm thinking some kid owned the car and beat the piss out of it, or didn't gap the rings properly.

Assuming you are using the M54b30 (or s52) crank, the displacement is 2,979 cc

Main Bearing Clearance: 0.0007- 0.0029
Connecting Rod Clearance: 0.0007-0.0029

Depending on your tune you could probably get away with #17 but for the amount of work you are doing, I assume you will want #21.

What are you doing for cams?

My stroker motor started with a m52b25 which is going into my 1996 328 so I will be using the m52b28 manifold, injectors and tune. I have a modified m52b30 intake cam in it.
I haven't installed the motor yet so any advice I have is only based on research so far but everything I have read lead me away from using the m54 oil control rings (bottom ring) which are an odd 2 piece design rather than the conventional 3 piece design. The M54's had a bad reputation for oil consumption and many believe that this 2 piece ring was to blame.

This can be solved by using the m52 or m50 oil control rings, note that the compression (top) ring for the m54 pistons is only 1.2mm tall versus the 1.5mm height of the m50 & M52 engines so you can't just order a regular set of M50/M52 rings, you need to custom order the rings to get get a set that has a 1.2 mm top ring, 1.5 mm middle ring and 2.0 mm 3 piece oil control ring. I bought a set of mahle off of ebay and just requested the configuration I wanted and it was no problem.

[M3blitkrieg]

The crank ring doesn't hit the block though. My m54b30 crank has it on it as it sits in the engine, in the car, with no hitting or fitment issues what so ever. It gets close when setting the crank, but it doesn't hit unless for some reason can't hold it straight.
And as a normal to engines, and somewhat new to bmws,.. a common lesson is ALWAYS hone, ALWAYS get new rings when changing pistons or blocks. As for the bearings, bmw had several bearing sizes that came out in various sizes depending on the specific block. So you can't for example use a green sized crank with a yellow dimensions block line bore. You can't just drop random cranks in random blocks with random bearings. Not unless you dont care about it being reliable, right, or working properly.

[M3blitkrieg]

Just to add on out of personal experience I had with my build, even though I have it together and not turned over yet. I found oversized piston from another member on eBay for $300. I found crank bearing set that luckily matched my green bearing block and green bearing cranks for about $175. A full gasket kit was $180. The block bored and cleaned and checked for $175. Plastiguage about 8 sticks worth making sure I had a mix of used bearings and brand new bearings in the exact best/right place as a bearing set only come with 6 or 8 half shells. Rod bearings are the same.

- - - Updated - - -

And that's pretty much as cheap as it here if you want the stroker. It certainly would have doubled in cost if I needed more block work, if my crank and line bore didn't match as close as it did, if the crank needed a turn and oversized bearings, if my rod pins where worn. It could easily be a $2500 cost if you don't happen to get the correctly sized block, crank, ect.

[Johnsonmjm]

I ended up buying white sized bearings and ended up with .001 clearance after plastagauging. So got lucky there. With the crank pulley on I can turn it and it is 120% smooth. Which is normal, especially with the assembly lube I used.

Block is already honed, and I think I will be running the piston rings as they are. I'm not worried about rings with less than 300 miles on them. The end gap and side clearance was perfect. Plus the rod bearings still had the coating on them, so they weren't even 100% broken in. New rod bearings and ARP rod bolts should do the trick nicely. I also plan on running a rev limit at 6200. 3500 for break in.

[spyderg0d]

I got lucky with mine too. The random junkyard pulls I got all came out perfect matching sized parts. It took me about 4 sticks of plastiguage to fit the bearings as best as possible tho. Finding plastiguage was the hardest to find thing in the entire build lol.

[samy01]

"plastiguage" ? maybe it would have been easier to find if you looked for plastigage

[Johnsonmjm]

Which block did you use the M50 or M52?

Just to add on out of personal experience I had with my build, even though I have it together and not turned over yet. I found oversized piston from another member on eBay for $300. I found crank bearing set that luckily matched my green bearing block and green bearing cranks for about $175. A full gasket kit was $180. The block bored and cleaned and checked for $175. Plastiguage about 8 sticks worth making sure I had a mix of used bearings and brand new bearings in the exact best/right place as a bearing set only come with 6 or 8 half shells. Rod bearings are the same.

- - - Updated - - -

And that's pretty much as cheap as it here if you want the stroker. It certainly would have doubled in cost if I needed more block work, if my crank and line bore didn't match as close as it did, if the crank needed a turn and oversized bearings, if my rod pins where worn. It could easily be a $2500 cost if you don't happen to get the correctly sized block, crank, ect.

[M3blitkrieg]

M50 I think. The only difference is the crank sensor boss for obdll, right? It didn't have that hole.

[Johnsonmjm]

M50 I think. The only difference is the crank sensor boss for obdll, right? It didn't have that hole.

Correct. The m52 uses an internal crank sensor. M50 uses the crank pulley as the reluctor wheel