M52B28 into M50B25

[Brianmoooore]

I know all the info is on here somewhere, but I'm spending too much time sorting out you lots' E30 problems to find the time to look.
Could someone who knows please give a quick rundown on what's involved and needed to rebuild a M52B28 into a M50B25 (or even M50B20) block.

[E30BeemerLad]

Dan will be the man for this one

[chu346]

Took this from e30.de hope it helps, translated from
http://wp1016621.wp027.webpack.hosteuro ... f01140.htm

The M50B25/TÃa is due to the price / performance ratio and a simple electrical connection, the most widely used engine in the E30 24V conversion. Just as the M20 engine in transforming to 2.7 liters erstärkt clear, this is also the case of the M50 engine. A variant with 2.8-liter M50 is the easiest and cheapest to build.

Variante 1 auf 2.8l Option 1 on 2.8l(Base Graugußblock M50B25)

KW 328i/528i from 84mm, 130mm Conrods (from the M20) and the Pistons M50B25 (Mahle No 84V136) without Vanos. Compaction then about 10,6:1 (10:1 series).

Variante 2 auf 2.8l Option 2 on 2.8l (Base Graugußblock M50B25tÃa)

KW 328i/528i from 84mm, 135mm connecting rods and pistons from M50B25tÃa with Vanos (Mahle No 84V166).

With a 84mm KW, the Pistons 4.5 mm higher out what by 5mm shorter (135er) Conrods again and will result in a compression of approximately 11:1.

If the compression value is too high, you can even a little hollow with a diameter of about 70mm in the flask. The depth depends on the desired reduction.


Variante 3 auf 2.8l Option 3 on 2.8l (Base Alublock M52B25)

KW 328i/528i from 84mm, 135mm connecting rods and pistons from M52B28 (thus M52B28)
10.2 Compaction


Conclusion:

The 2.8 liter conversion is the easiest and cheapest way to more torque and power. With a good exhaust system, revised camshaft control and well-made, around 245PS drin. A car from my friends reached 244 hp 303 Nm (Dbilas intake cam, chip tuned, BOSCH Motronic, 325i 24V intake, leergeräumte catalysts M3 E36, E30 M3 Endtopf, original air filter box).

[DanThe]

I take it you have an M52 with fooked bores Brian? First thing to check is the state of the pistons and if they are good enough to be reused, really the only non compatible parts are oil pump and chain tensioner guide rail. 2 litre block rebored gives the best bores

[Brianmoooore]

Thanks for the reply, Dan. I don't actually have any 2.8's with fooked bores yet, but I have the possibility of acquiring a pair of them soon, and want to know what the possibilities with them are.
I've a M50B20 non vanos that's been lying around for years, donating the odd special bolt and odd part to B25s, plus the odd incomplete M50B25 Tu.
Assuming the pistons aren't damaged, are the ones from a Nikasil M52 suitable for fitting to iron bores? I suspect at least one of the M52's is a linered one with a sunken liner. Are these pistons suitable?
You say the oil pump is different and tensioner guide rail are different. Is that overcome by just retaining the M50 parts?
Low cost is important in all of this, otherwise I may just as well buy complete E36 2.8s with known good engines and take the engines from them.

[DanThe]

Yep, keep the M50 bits, either pistons are fine

[rob0r]

Interesting information. I have thought about doing this somewhere down the line to my non vanos M50b25. From reading that I gather all I'll need is the 2.8 crank and M20 conrods. Are M20 conrods all the same length? I possibly have access to E21 M20b20 or b23 conrods rather easily. With my non vanos, will any changes to the engine management be neccessary?

Thanks

[Brianmoooore]

The particular M52B28s I was after were on ebay, ending tonight. Because of the weather (and in particular, an E30's lack of traction on sheet ice), I arrived home ten minutes too late!!!
They went on the one and only bid as well!
Ah well, there'll be others.

[DanThe]

Ive just spent 5 mins searching for them, must have been a very bad advert! Got a link??

[Brianmoooore]

I've already deleted it! Look for LPG cars, and BMW. It was an E36 on an 'S', with a faulty engine, a spare engine, and LPG.

[DanThe]

That truly was a bargain for someone,
Over 1800 look ins and only 1 bid!