Before I start I would like to point out that I know it may be best to just pop a 3.2L engine and save the hassle. However, where I am residing now, changing the engine block is a hassle with the dept of transportation. It has got to do with the engine number registration and they make it real hard for you to swap motors. Anyway, to cut a long story short - changing the block is NOT an option. The original engine block MUST remain. Everything else is ok.

I am not a BMW expert so please forgive me if I ask silly questions! Ok, here goes...

I just want to get the most oomph from my current engine - an M50B25TU which is already stroked to 2.8L. No overboring was done - just changed the crank, piston and rods. So, as time went by I felt I wanted more power and the only way to do (with the limitation I had mentioned above) it is by stroking it to the max to 3.2L.

So I need to know what exactly are the parts I need to get the engine running. I know I need to overbore it to 86.4mm to fit the pistons. From what I was told I only need the 3.2L crank, pistons and rods. Does it have to be from a S50 or S52? Or does it not matter? Is there anything else? What about the cams? Do I need the cam trays? Like I mentioned above the block must stay but if needed I could change the head.

To summarize my intentions - I am looking to stroke my M50 engine to 3.2L. What do I need to do?

I'm open to any suggestions. I may have overlooked some vital information so please enlighten me.

Oh, some of my car's specs are in my signature.

Please :help !!

Thanks!

Something I'd like to know for sure aswell.

Heres my 2p worth anyway.

You need to bore the block out to 86.4mm like you say, S52/M54 B30 crank, S52 pistons, I believe the rods are the same (135mm). That should in theory should then give you a DIY S52 motor.

pretty sure this is impossible

You need an S52 crank or a 3 liter M54 crank (same part). You can use the 135mm rods you already have. You need S52 pistons.

The stuff above is correct, and you can bolt the head on as well. Maybe you want to buy an S52 and sell the block after you are done swapping the parts???? Obviously, you will need a custom chip made for this application.

Why would he need to change the head?

I know I need the 3.2L S52 crank, rods and pistons. And I need to overbore my M50 block to 86.4mm to accomodate the pistons.

Of course I need a customized chip too.

Anything else I can use from the S52 motor? What about the cams? Lifters? Like I said, I can change everything except for the block.

By the way, both the Euro M3 and US M3 are 3.2L, but why is it that one makes only 240 hp while the other makes 320 hp?? How much power am I likely to make with my conversion? On the 240 side or 320 side??!!

Anyone? :help

Info on Euro vs US M3 is all over the web. Just google it and find out about the throttle bodies, etc.

Info on Euro vs US M3 is all over the web. Just google it and find out about the throttle bodies, etc.

+1

if all works out, your engine would be more similar to the u.s. 240hp.

Info on Euro vs US M3 is all over the web. Just google it and find out about the throttle bodies, etc.

Just the 6 individual throttle bodies makes the 80 ponies difference? This feature and the fact it has double vanos is all that is mentioned in the web about the physical difference between the two engines (from my googling, anyway). It can't be just that, can it??

No, but it certainly makes the engine VERY responsive. The 80hp comes mostly from the cams, the better flowing head, headers and the throttle bodies. Not to mention the fact the euro M3 makes its peak HP about 1000rpm higher than the US counterpart.

Just get the crank and pistons from a 3.2 and take it to a REPUTABLE MACHINE SHOP! DO NOT CUT CORNERS HERE! There are so many adjustments that have to be made when installing a foreign crank in a used block. I have done it in my shop many times. Please dont get the idea that you are going to hand any machinist 1 3.2 piston, pay him $15 a bore to fit the piston, and then take it home and slap the 3.2 crank and rods into your block. Try to picture trying on a friends shoe. Chances are, even though he may be the same size as you, he broke it in differently; and it will fit funny.

Take the whole block to an excellent machinist, and have him do a align bore and adjust all of the journal caps with the fresh main bearings. This will ensure excellent oil pressure at idle, and less friction. You can bet that the same shop wont make a common mistake of tapering the cylinders while overboring them ( your new piston rings wont make it to 10K miles if this happens).

If you are using an OBD1 Intake manifold and injection, and M3 cams, you can expect about 270hp. Make sure if you are using the 3.2 cams, that you get the cam trays to go along with it. You can get it closer to 300hp with a good set of shrick/sunbelt cams, software, headers and full exhaust.

No, but it certainly makes the engine VERY responsive. The 80hp comes mostly from the cams, the better flowing head, headers and the throttle bodies. Not to mention the fact the euro M3 makes its peak HP about 1000rpm higher than the US counterpart.

Just get the crank and pistons from a 3.2 and take it to a REPUTABLE MACHINE SHOP! DO NOT CUT CORNERS HERE! There are so many adjustments that have to be made when installing a foreign crank in a used block. I have done it in my shop many times. Please dont get the idea that you are going to hand any machinist 1 3.2 piston, pay him $15 a bore to fit the piston, and then take it home and slap the 3.2 crank and rods into your block. Try to picture trying on a friends shoe. Chances are, even though he may be the same size as you, he broke it in differently; and it will fit funny.

Take the whole block to an excellent machinist, and have him do a align bore and adjust all of the journal caps with the fresh main bearings. This will ensure excellent oil pressure at idle, and less friction. You can bet that the same shop wont make a common mistake of tapering the cylinders while overboring them ( your new piston rings wont make it to 10K miles if this happens).

If you are using an OBD1 Intake manifold and injection, and M3 cams, you can expect about 270hp. Make sure if you are using the 3.2 cams, that you get the cam trays to go along with it. You can get it closer to 300hp with a good set of shrick/sunbelt cams, software, headers and full exhaust.

Now that's what I was looking for. Some useful information! Thanks buddy.

Yeah, I would definitely take the block to an experienced machinist. I wouldn't want to have the problems you had described. Oh, btw, why would one make the mistake of tapering the cylinders while overboring the block?

Since I am converting from an M50 I will be on OBD 1, inlet and outlet manifolds and injection system. Following your advise, I will need to change my 3.0 M3 cams to 3.2 ones.

I'm not very mechanically inclined so can you explain more about "have him do a align bore and adjust all of the journal caps with the fresh main bearings"? Is there any layman's terms for align bore and journal caps?!! (duhh...!!) That will help me remind him about the requirements.

Am I pretty much set? From what I gather from your comments I need to get the S52B32 crank, piston, rods and cams (and trays to fit).

Thanks again for the enlightenment!

Now that's what I was looking for. Some useful information! Thanks buddy.

Yeah, I would definitely take the block to an experienced machinist. I wouldn't want to have the problems you had described. Oh, btw, why would one make the mistake of tapering the cylinders while overboring the block?

Since I am converting from an M50 I will be on OBD 1, inlet and outlet manifolds and injection system. Following your advise, I will need to change my 3.0 M3 cams to 3.2 ones.

I'm not very mechanically inclined so can you explain more about "have him do a align bore and adjust all of the journal caps with the fresh main bearings"? Is there any layman's terms for align bore and journal caps?!! (duhh...!!) That will help me remind him about the requirements.

Am I pretty much set? From what I gather from your comments I need to get the S52B32 crank, piston, rods and cams (and trays to fit).

Thanks again for the enlightenment!

Its very common for inexperienced machinists put too much pressure on one side of the bore, or to try and bore too quickly. An experienced machinist will take his time and not rush.

S50 cams will fit in M50 cam trays. S52 cams need cam trays from a M52 or S52 engine.

Well, they are no real layman's terms for align boring the and adjusting the main caps... When he installs the crank in the block, he should be able to tell whats needed. For example, when the crank is torqued down and installed with the new bearings, you should be able be able to rotate the crank by hand easily. If you cant, you usually have the crank align bored (I have seen some blocks with .004" of distortion ).

Adjusting the bearing caps is only done if the clearance in the main bearings is found to be excessive, and is done at the machinists discretion.

I am actually considering selling my 3.2 rotating assembly(crank, rods and pistons), along with s52 cams and camtrays. Engine had around 60k miles. Shoot me a fair offer if you are interested....

Do you have certain about M54 and S52 crank is the same? If i know correct, the M54B30 uses 89mm crank and the S52 uses 91mm crank..


Im looking for similar project.. but i have doubts to stroke and rebore it to 3.0 or 3.2... the second option will give more power, but a very badder rod angle ratio and with higher pistons speedy..

If you want an over bore engine, you can always install 3.2 pistons with a 2.5 crank. Has anyone ever installed the 3.2 pistons in a ROW 320i (2.0 6 cyl E36)? You would get a very high revving engine with a displacement slightly less than 2.5l...

This is awesome because i was just considering the same scenario for my 95 325is. Where are these parts available?

thinking about doing something simular in the z3 :)