M50B25 or M52B28?

[Jamesb318is]

As per title really, what are your opinions on the most worthwile conversion?
Things i can think of so far -
M50
-Cheaper
-Stronger iron block
-Easier to fit as can be sourced from an E34

M52
-More power, (and more scope for even more power thanks to the manifold and throttle body mod?)
-Vanos (flatter torque curve)

My reason for asking is that i want to do this conversion, but dont want to go for an M50 and be dissapointed.

[jmc330i]

Im asking myself the same question at the moment.

My problem is it would need to be a quick conversion, so I would go with whichever I can get my hands on first - most likely an E34 M50.

But if I had time to find the E34 sump, M50 manifolds etc, I think I would go for the M52. The EWS doesnt bother me and the extra bhp/torque would be most welcome.

[JMRe30]

isnt the biggest advantage of the m52 the less weight of the alloy block? i would definately go with an m52.

[DanThe]

The alloy block is probably the worst feature of the M52

[Brianmoooore]

If you have access to both, then the 2.8 is obviously the better conversion.
M50B25 is easier and cheaper to get hold of, comes in both vanos and non vanos flavours, can be obtained with the correct sump and pick up already fitted, and is far easier electrically to fit.
M52B28 is going to be more expensive, has the Nickasil question hanging over it, needs a fresh inlet manifold and ECU chip, and has the EWS stuff to deal with.

[DanThe]

Or buy both and refurb the M50 with the M52 'good bits'

[fuzzy]

go big with more tuning scope to avoid future disapointment

[m-dtech]

im going m50 turbo on a m50b25 but need to look at compression ratios

[DanThe]

Standard compression ratio is about 10.2:1 I think mate

[Jamesb318is]

So far you've pretty much backed up what ive been thinking, looks like im going to be on the lookout for a m52b28 lump!

Fuzzy is absolutely right, if im gonna do this swap i might as well do it properly, to avoid future dissapointment!
Cheers guys.

[Dan318-is]

The alloy block is probably the worst feature of the M52

Explain?

[maxfield]

The alloy block is probably the worst feature of the M52

Explain?

was it nakasil problems or was this on earlier cars?

if its not then its much lighter than iron

[Jamesb318is]

Yep, possible nikasil issues, and the blocks are weaker (most of the m52's ive seen at work with the heads off strip the blocks when re-torqueing.)

[Dan318-is]

Yes but m52's around now surely would have surpassed that issue? and most of them had the liners replaced with alusil ones did they not? Iv also read in places that if you let them fully warm up each time you start the car they dont fail although that might have been five series lumps only

i would go m52 anyday

[DanThe]

Not to mention the liners that move around causing the head gasket to let go like my 2.8

[Jamesb318is]

Hmmmm, decisions decisions! More power + less reliability = a hard choice!

[Toby_Unna]

Or buy both and refurb the M50 with the M52 'good bits'

if i'm right the 2.5 and 2.8 have the same diameter pistons?

can you therefore use the 2.8 crank in an 2.5 m50?

mildly tuned m52b28s are a powerful and fantastic sounding engine, but i wouldn't touch one. choose between shagged nickasil bores or sinking liners

[DanThe]

if i'm right the 2.5 and 2.8 have the same diameter pistons?

can you therefore use the 2.8 crank in an 2.5 m50?

Yes and yes

mildly tuned m52b28s are a powerful and fantastic sounding engine, but i wouldn't touch one. choose between shagged nickasil bores or sinking liners

Which is why I am partaking in the above

[Toby_Unna]

i've thought about that before

seems like a f***ing good idea to me. m50 strength, 2.8 power.

with the manifold swap those 2.8 m52s go bloody well. (i.e. they make an e36 4dr quicker than my old m535i despite similar weight)

are the heads/valves/cams different/interchangeable?

i like your thinking anyway

[DanThe]

The heads are different

M50 is what im using, inlet cam has 1mm taller lobes than M52, valve stems are thicker, timing is also slightly different, double valve springs, and the valves protrude the head face unlike the M52 which means more compression



Im also planning on decking the block to crank the comp ratio up even more but I dont know how much yet until ive got the crank gear in the iron block

[Toby_Unna]

so are you expecting better power than a stock 2.8 m52 using the m50 head?

given the number of 328is with bore/liner problems, this would appear to be the perfect solution. sod the few extra kilos, it will make bugger all difference (unless your name is demlotcrew )

[Jimbob]

Apart from the potential risks with using an M52 2.8 block, could you not just mate this up to an M50 2.5 head and everything else?

[kam-325i]

They are'nt using the M52 Block, just the crank from the M52 into the M50, i think........

[m-dtech]

im gonna stick with my 2.5 non vanos and turbo lol, i have been saying this for aaaaaages.

should be on the road late january.

[kam-325i]

Helping & Seeing SteveTiggers M50 conversion made my mind up....

Just got to what a while longer now...

[DanThe]

Well they say 220 with the M50 inlet, so I reckon 230 at least

unless your name is demlotcrew

Tut tut

If I was that bothered about 20 odd kilos Id go on a diet

Apart from the potential risks with using an M52 2.8 block, could you not just mate this up to an M50 2.5 head and everything else?

Yes the head gaskets are the same part No

[Toby_Unna]

im gonna stick with my 2.5 non vanos and turbo lol, i have been saying this for aaaaaages.

should be on the road late january.

pictures so far?

[Jimbob]

Soz I meant would it be possible to just use a complete 2.8 block and attach the 2.5 head.
Tis a bonus about the piston sizes though. I want to do this but with an even match of time and £Â£ so I need to cover all angles before assuming costs

[Jimbob]

Thanks DanThe!

[Toby_Unna]

Yes the head gaskets are the same part No

so simplistically, is it really as simply as using m50 bare block with m52 everything else and get bulletproof 2.8 mill?

that sounds very good.

[DanThe]

so simplistically, is it really as simply as using m50 bare block with m52 everything else and get bulletproof 2.8 mill?

that sounds very good.

Which is basically a US 2.8, they didnt get early alloy blocks due to their worse than our crap fuel

[Toby_Unna]

learn something everyday...

i assumed that US engines refered to as iron block was a mistake. obviously not

liking this idea

[Andyboy]

Or buy both and refurb the M50 with the M52 'good bits'

You've hit the nail firmly on the head M'Boy! The 2.8's are a bit iffy; on one hand the Nikasil block drama and on the other, the blown headgasket on steel liner engines. What happens is that the alloy can sink around the steel liners between the cylinders. They can be fine, or a load of shit, basically.

So, a troubled 2.8 with Nikasil/head gasket issues for peanuts is a plan. Then rebuild it using a standard 2.5 iron block and use whatever head you want.
To be honest though if I had a 2.8 crank at my disposal I'd be sticking it into a 2.5 M20. Lovely high compression, almost no machining work, cheap to build and loads of torque. Lift the bonnet and it looks bog standard even down to the engine number.

[Andyboy]

Yep, possible nikasil issues, and the blocks are weaker (most of the m52's ive seen at work with the heads off strip the blocks when re-torqueing.)

Only when you use the wrong head bolts - i.e the ones for the iron blocks. Unless the engine has been seriously cooked the correct head bolts should torque up okay. The problem comes from the non BMW 'universal' head bolts which are slightly shorter. The threads only engage in 2/3 of the threads on the alloy block, overload the threads and rip them out.

You cannot properly repair the threads and the engine is thus scrap.

From memory the 2.8 engines in the US were always alloy blocked. The iron block engine is the US M3 which is an M52 iron block unit using the bore and stroke dimensions of the European M3 (but the crank is different). These US M3's gave 240 bhp. The 3 litre used a stock 325i (big bore) inlet and the 3.2 was fitted with the small bore 320i manifold to restrict power and improve torque. Both used a standard 325i or 328i head and special cams. Both cars go very well indeed and the US M3 motors were the basis of the Alpina E36 and E46 engines. The Alpina Z4 Roadster S uses an iron block M52 3.2 litre with special cams and give about 250-260 brake. It's also a lovely engine to use, loads of grunt.

[Toby_Unna]

To be honest though if I had a 2.8 crank at my disposal I'd be sticking it into a 2.5 M20. Lovely high compression, almost no machining work, cheap to build and loads of torque. Lift the bonnet and it looks bog standard even down to the engine number.

sod that! you'd have to spend a fortune on a 2.8 m20 to get a solid 220bhp, whereas you'll get it from a standard m52 with just the inlet manifold swap and a chip