M50 Stroker

[CMBusch]

I apologize for asking so many questions. Unfortunately, I have many more questions that doing a search has not answered.

Would it be possible to make a stoker out of a M50B25TU with M52B28 crank and rods? Has anyone done it before? What is the compression ratio going to end up being, 11.X?

[pazi88]

Yes it possible. Compression is something between 10 and 11.

[Bimmerguy91]

Or you can use M54B30 crank, rods and pistons a have a 10.3:1 3.0 liter stroker. I've got the parts if you need them.

[nrubenstein]

When you can buy an S50/S52 for $1000-2000, why would you build a "stroker?"

[CMBusch]

Yes it possible. Compression is something between 10 and 11.

Awesome! Thanks for the info. I've heard that the M52 crank with the 140mm M50B25TU rods would be too long, and that the M52 rods don't fit with the M50B25TU pistons. Is any of this true? I've been having a hard time finding any information.

Or you can use M54B30 crank, rods and pistons a have a 10.3:1 3.0 liter stroker. I've got the parts if you need them.

I'm good thanks, I already have the parts available.

When you can buy an S50/S52 for $1000-2000, why would you build a "stroker?"

Because I'm building a M50 I got for free and the parts to do the stroker are $200.

[nrubenstein]

Awesome! Thanks for the info. I've heard that the M52 crank with the 140mm M50B25TU rods would be too long, and that the M52 rods don't fit with the M50B25TU pistons. Is any of this true? I've been having a hard time finding any information.



I'm good thanks, I already have the parts available.



Because I'm building a M50 I got for free and the parts to do the stroker are $200.

By the time you sell the M50, buy those parts, spend the money for the other crap you'll need to assemble the motor, you'll easily be past the low end of my range. What about cams? You going to keep the stock ones there, too?

And if you need any machine work at all, that's another big chunk. Or just pick up an M52B28 for a few hundred bucks.

[pazi88]

Awesome! Thanks for the info. I've heard that the M52 crank with the 140mm M50B25TU rods would be too long, and that the M52 rods don't fit with the M50B25TU pistons. Is any of this true? I've been having a hard time finding any information.

Because I'm building a M50 I got for free and the parts to do the stroker are $200.

Yes the 140 m50b25tu connecting rods are too long. But m52 135mm connecting rods fit without problems and with those you get the compression ratio between 10 and 11 which is fine.

For that price it's worth building and with 200 more for seals etc. you can get running engine if you resuse some parts what you "shouldn't". But if you know what you are doing, it's fine.

[CMBusch]

By the time you sell the M50, buy those parts, spend the money for the other crap you'll need to assemble the motor, you'll easily be past the low end of my range. What about cams? You going to keep the stock ones there, too?

And if you need any machine work at all, that's another big chunk. Or just pick up an M52B28 for a few hundred bucks.

True, but I'm just trying to make this motor better while I have it apart for the rebuild. Not to mention I'll essentially have a new motor when I'm done. S50s around me are 2k with over a 100,000 miles on them. I've already had the head and block checked, cleaned and resurfaced so that's not longer an issue.

I keep doing the "While I'm in here, I should replace..." so the parts list keeps growing. I'm keeping the cams for now but I intend to upgrade to S50 cams when I have the chance. I also have a set of S50 springs and hardware that I'm not sure if I should use. I know that M50 springs are stiffer but for NA I've been told that S50s are better..?

I get what you're saying but if I stuck with that logic, I would've never bought a E30 first place. From a financial standpoint, buying an old BMW to dump money into is beyond stupid.

Yes the 140 m50b25tu connecting rods are too long. But m52 135mm connecting rods fit without problems and with those you get the compression ratio between 10 and 11 which is fine.

For that price it's worth building and with 200 more for seals etc. you can get running engine if you resuse some parts what you "shouldn't". But if you know what you are doing, it's fine.

Yeah, that's what I've found. However, is it true that M50B25TU pistons won't fit on M52 rods because of the wrist pin placement?

Yeah, It's actually $150 but I'm picking up another M50 block for $50 as well. I'll have 3 M50B25TUs now... I should probably stop. I'm doing a full rebuild on this motor, but I'm not yet sure if I have everything (hence my other thread). What are the parts that I "shouldn't" reuse?

[pazi88]

The connecting rods will fit. No problems. You can pretty much mix and match all parts from m20 to m54 because those share same basic dimensions.

The m50tu springs are just fine if you are not doing anything crazy like revving it to 8k or up. The springs and the whole valvetrain are in the order from worst to best: m50nv, m50tu, m52. If remember correctly the us s50 springs = m50tu springs and us s52 springs = m52 springs.

And yes the double springs from m50nv are stiffer than m52 springs but the stiffnes is not the only thing you need to know from them. The double spring design is ancient and the second spring is only needed to keep the valve from bouncing back open when it closes. In m52 this is acheived by conical shaped spring and it can be less stiff to make same impact. Which leads to less power loss in valvetrain.

But to be short: The stock springs are fine if you don't rev it over 8k or have some crazy 300 degree cams or have boosted engine with 2bar of boost.

And for the parts you shouldn't reuse, for example it's recommended to change all the bearings. But if the old ones don't show wear you could reuse those. Also if you have metal gaskets for example it the chain cover. You can reuse those. Also you can reuse the shaft seals. You only need to replace rubber and paper gaskets and headgaskets. But you "should" replace all gaskets, seals and bearings.

BTW I may have same problem as you collecting the m5x parts :D https://www.instagram.com/p/0yWgMOnDyV/

[CMBusch]

Cool! I'll pick them up this weekend then.

Yeah I was gonna do 7,000 at most. I was just tempted to use the S50 springs because I believe they're newer. I thought S50 springs were the same as S52 springs. I know that the m52 springs were also conical, but longer. That's interesting about the M50NV spring design though. Anyway, I got all my info from here.

Haha yeah, those are all cheap enough to just buy. Putting it all back together to find out that the rear main seal leaks would suck. Even the bearings aren't too terribly expensive. I'm replacing the timing chains, guides and tensioners as well. Was thinking about lifters as well, but I'll just clean them and hope for the best.

Haha you got a lot parts. I'm just starting my collection. I'll have 3 M50s and a M10. I kinda want to build and boost the M10 when I have the money. By the way, I stumbled upon your youtube channel. Cool videos!