More Displacement Out Of A Non-Vanos M50?

[Low Level E30]

Can a non-Vanos M50 be bored out to fit S52 pistons?

If so, what work needs to be done to the non-Vanos head to work w/ an S52 rotating assembly?

[FredK]

Yes, in fact the non-Vanos block is the only M50 that can be bored past ~85mm. I would assume the M50 non Vanos head can be left alone, and any mods for valve clearance (if any) would have to be made to the pistons.

I seriously considered this possibility, except I wanted to use S50 components. The problem is cost. The cost of the various bottom end components add up quickly. Out of the M50 based head gaskets, the S52 is the most expensive.

Also, the NV M50 doesn't have knock sensors, and you'd have to get custom tuned software for the engine. It is more cost effective to get a S50 as complete as possible.

If you're located in Germany, piecing the engine together like you describe might be the only way to go. The M54 crank has the same stroke as the S52 (89.6mm), and might be more readily available overseas, as the S52 was a US only kind of thing.

[Low Level E30]

Yes, in fact the non-Vanos block is the only M50 that can be bored past ~85mm. I would assume the M50 non Vanos head can be left alone, and any mods for valve clearance (if any) would have to be made to the pistons.

I seriously considered this possibility, except I wanted to use S50 components. The problem is cost. The cost of the various bottom end components add up quickly. Out of the M50 based head gaskets, the S52 is the most expensive.

Also, the NV M50 doesn't have knock sensors, and you'd have to get custom tuned software for the engine. It is more cost effective to get a S50 as complete as possible.

If you're located in Germany, piecing the engine together like you describe might be the only way to go. The M54 crank has the same stroke as the S52 (89.6mm), and might be more readily available overseas, as the S52 was a US only kind of thing.

Thanks for the good info!

I was looking to use S50-everything, ideally, to build a 3.0L non-Vanos motor. From what I've found so far, S50 and S52 rods / pistons are interchangeable - difference really comes from the cranks. Figure 350 for rods / pistons, and 300 for the crank, and then the head gasket. What else do I need, really? $800 isn't that bad. Then spend a li'l more to get a chip burned -- coming in at around a thousand bucks.

[streetknight]

im building a nv m50 i have s50 crank,stock nv 140mm rods, and later m50 pistons. brings compression about 10.5:1 displacements at about 2.9l going to run ms+s with custom knock. hopefully get around 230-40hps.

[FredK]

Yep, the S50 and S52 rods are interchangeable, as they're both 135mm long. I believe the S52 crank runs a tad more than the S50 crank, closer to $500.

Anyway, here's a sample parts list (of the major parts)
Boring and honing $200 - 250
S50 crank $350
S50 pistons and rods $300
piston rings $180
main bearings $60
rod bearings $50
rod bolts $40 (you MUST replace these. they are one time use stretch bolts)
main bolts $15
head bolts $15

I guess you might be able to get away with reusing the piston rings if the pistons have sufficiently low mileage. However, they will have wear patterns from the previous block and may not have the best sealing against your newly bored and honed M50 NV block.

The total is around $1200. If you get a custom tune, that will bring the budget to $1400 or more. You can get a complete low mileage S50 bottom end for that price. Of course, if you're located in Germany, shipping a bottom end might be fairly expensive.

On the plus side, I guess you will end up with a mostly new bottom end that will last a long time. :)

[Low Level E30]

im building a nv m50 i have s50 crank,stock nv 140mm rods, and later m50 pistons. brings compression about 10.5:1 displacements at about 2.9l going to run ms+s with custom knock. hopefully get around 230-40hps.

Why the later M50 pistons?

[FredK]

Hmm, I'm almost certain that NV rods are 135mm. The M50TU rods are 140mm. Thus, the pin height on M50TU pistons are different than on the NV pistons.

Maybe he meant M52 pistons, because if you put the S50 crank in, the pistons would probably crash into the valves being around 11mm higher at TDC. There's only a 1.8mm difference in stroke between the M52 and S50 cranks.

[Low Level E30]

I don't have an M/S52 crank to look at --- is it true that only an S50 crank can be fitted to an M50? I read somewhere that M/S52 cranks cannot be used in an M50... ?

I'm 95% certain also that NV rods are 135mm, as you said.

How do S50/2 pistons compare in weight to NV M50 and M52 pistons?

[Low Level E30]

Probably a better bet to start w/ an M52 block, and just add a non-Vanos head, huh?

Is there a mounting point for a non-Vanos crank position sensor at the front of the M52, or would one have to be tapped? Or, can I just use the nV CPS at the back of the M52?

[BimmerToad]

Since the rod lengths are the same and the crank strokes are different for the S50 and S52, I highly doubt the piston pin hole is at the same height. If they were, the S52 would either have an insane compression, or not be too cylinder head/valve friendly.

Also, why does everyone want to use a NV head? Dual valve springs stock sure, but if you're building up a motor, wouldn't you replace the valve springs anyway, and there are quite a few aftermarket suppliers of valve springs for the Vanos heads. The vanos heads have a smaller valve stem, which makes the valve lighter, and the later heads have a lighter lifter assembly. Overall, I think the vanos head would be better suited for high rpm applications (with a lighter valvetrain). Besides, if you have a vanos head and you still don't like vanos .... disconnect it :)

Just my $0.02

[BimmerToad]

Probably a better bet to start w/ an M52 block, and just add a non-Vanos head, huh?

Is there a mounting point for a non-Vanos crank position sensor at the front of the M52, or would one have to be tapped? Or, can I just use the nV CPS at the back of the M52?

The M52 block (or is it the timing chain cover) has a mounting point for a front mounted CPS, and I assume the NV and Vanos sensors are similar in size.

[streetknight]

sorry your right had just woken up when i wrote that. they are 135mm. but your going to have to run different pistons with the s50 crank the piston on a s50 are shorter by about 4mm you canot shave 4mm out of a nv piston. if you do shave them ur upper ring will be about 1/2mm away from the top. the later m50 pistons have the wrist pins in a different spot. ill take a pic on monday when i go to work. but all and all with the later m50 pistons you have clearance from the valve touching the piston top.
i picked up later m50 rods and pistons for 40bucks. which is alot cheaper then the 300 for s50 pistons and rods+ i dont have to bore out the block they fit right in and ill be at 2.9l. but i dont have to spend extra cash on boring it out.

[streetknight]

Since the rod lengths are the same and the crank strokes are different for the S50 and S52, I highly doubt the piston pin hole is at the same height. If they were, the S52 would either have an insane compression, or not be too cylinder head/valve friendly.

Also, why does everyone want to use a NV head? Dual valve springs stock sure, but if you're building up a motor, wouldn't you replace the valve springs anyway, and there are quite a few aftermarket suppliers of valve springs for the Vanos heads. The vanos heads have a smaller valve stem, which makes the valve lighter, and the later heads have a lighter lifter assembly. Overall, I think the vanos head would be better suited for high rpm applications (with a lighter valvetrain). Besides, if you have a vanos head and you still don't like vanos .... disconnect it :)

Just my $0.02

the reason im building a nv is because i am running megasquirt now and want to keep using it just have to add a knock sensor. this way i dont pay for some one else tuning my car.

[BimmerToad]

Makes sense. MS with a nonvanos 24v would be a nice setup, if you get the tuning down. Can MS be programmed to handle adjustable valve timing?

[streetknight]

personally i dont know ppl om the ms board say it can be done but i dont know i want to keep it simple and cheap. main reason ms works for me is because i can set up cop with ms, that was the seller there.