Built M50 vs S50 swap

[browlciba]

I’m starting to get to the point in my project E30 where I’m going to seriously think about engine swaps. (1989 325I M20b25)

I like the idea of a highish strung N/A motor, running a highish compression (I come from a background of my old man building drag cars in the 80s)

Eventually the possibility of adding a small turbo

So, M50s are cheap as dirt, and very accessible

S50s cost quit a bit more
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And honestly I don’t see THAT much of a difference

With the assumption that I’m going to be completely tearing down the motor and rebuilding it anyways, is there really any reason for me to shell out the cash for an S50?

S50 cams are good, but I’d probably be going bigger anyways.

I can swap out an S50 intake and head on an M50

And the M50 has thicker cylinder walls for when/if I add boost

My goal is ~250-260 hp N/A. Most people say thats pretty steep but this is not a daily driver, and I’m willing to give up drivability and gas mileage for thicc cams and high compression

S54/M54 would be great, but thats a huge jump in price and from my understanding, a clusterfuck of swapping OBD2 and OBD1 electronics

What do you guys think. I’m still somewhat new to the world of BMWs so I may be wrong about some of this

[steve_k]

sounds like you've got a plan sorted in your head on what to want do.

there's been a few on here who have built a 3L m50 stroker which seems to put down pretty good power,
have a search on here for 3L m50's as i know there's a couple of threads.

good luck with it.

[flybynite]

Another option why not build the M20 stroker? you could possibly put a small turbo on that and keep it original?

Like all these 'best engine' threads it all comes down to where you are and what you use it for. If you are somewhere roads are more straight than bent then handling is not as important as straight line speed (sounds like you are Stateside) Here roads are bent so handling is more important. S50 did nothing for the handling of the E36 and I drove one for 10 years, having tried one it does even less for the E30.

As far as power goes then it again comes down to what you want. If you want to drive everywhere leaving 11s behind you then fine but there is only so much power the back end of an E30 will take and driving a car at half throttle is not as much fun as driving a car with half the power at full throttle.

[JungleGus]

In your boat, I would 100% do a 2.9 M20 stroker for wide variety of reasons - lighter, more "original", sounds better, enough power, etc. Your power goals aren't crazy, you could probably get pretty close with a well done M20 stroker

I have the Alpina factory 3.3 M52 stroker and it's been a huge, huge effort to get it looking and running anywhere near a stock level - mine is decent now, but it's been a long journey. Plus, they are pretty old engines now so a big chunk of the ancillaries would need rebuilding/replacing for peace of mind.

My buddy has a 3.1 M20 race engine that puts down pretty crazy power (est 300hp+...the RH ITBs added 50+ hp alone) - if you really want to get wild. But a 250hp 2.9 M20 would be super reliable, look pretty stock, and drive really really well on a road car.

Happy to chat through if you want more of a thought process...I've tried to approach my car with keeping it usable. Have done around 2K miles in the last week with plenty more to go and I'm happy...but I'd be just as happy having spent a huge chunk less and knowing that pretty much the entire engine + ancillaries was rebuilt...and having better resale if I ever did decide to sell. Keep in mind there is a lot more knowledge out there now about builing M20 strokers than there used to be in the days where people built 2.7s and barely cracked 200hp

[steve_k]

as gus says above, a nice 2.9 m20 stroker would give you a good solid base to work from, also it would give you an as new engine,