will its fit

[hot 520i]

will a M50B25 cams fit into a M50B20 head?

[///Sniper535]

i doubt it

[Torque]

Will it physically fit? Probably. The ETK however doesn't show them as interchangable ... so even if it fits, duration and lift are probably way off.

[winfred]

i've not dealt with a 2.0 m50 but i have built many a 2.5 and 2.8, pretty much everything that bolts to one m50 style head will bolt to another, like now i am working on a 97 528 with a cracked head and i don't have any m52b28 heads, no m50b25tu's either, so i built a non vanos m50b25 head into something that would work for a single vanos m52 by changing the cams and boxes. so your cam swap will probably work, id look into the spec's on the cams to make sure that it's actually a upgrade before doing the work though, they may be the same

[hot 520i]

ok thanks. i will check into and let you know if it works. Now what about a 320i or a 325i 5speed man will it built on to my motor or will it need to be mod to fit?

[Ferret]

Yes, the B25 cams do go into the B20 head, I've done it.

However this was when I put a B20 Head on a B25 engine - the difference while it ran was amazing - engine revved a lot more freely and had a lot more power low down...

...but... the big ends went on cyl 3 and the motor self destructed :s

[ironie]

Yes, the B25 cams do go into the B20 head, I've done it.

However this was when I put a B20 Head on a B25 engine - the difference while it ran was amazing - engine revved a lot more freely and had a lot more power low down...

...but... the big ends went on cyl 3 and the motor self destructed :s

You mind a few questions on this, not that I intend to do it, But I am curious.
1) How long did it run with the 2.0 head on it?

2) Did you take measurements of the heads part of the combustion chamber
of both the 2.5 and 2.0 heads for comaparision.

I would suppose the increase in compresion was the power you felt, and the reason you spun the bearing, or did you actually break a piston arm?.
One would think the wristpin is the weak point.
A increase in compresion by a decrease of displacement is a novel way to go about it I guess

It sounds like a interesting experiment if one has the peices parts

Regards
Ron

[Ferret]

You mind a few questions on this, not that I intend to do it, But I am curious.
1) How long did it run with the 2.0 head on it?

2) Did you take measurements of the heads part of the combustion chamber
of both the 2.5 and 2.0 heads for comaparision.

I would suppose the increase in compresion was the power you felt, and the reason you spun the bearing, or did you actually break a piston arm?.
One would think the wristpin is the weak point.
A increase in compresion by a decrease of displacement is a novel way to go about it I guess

It sounds like a interesting experiment if one has the peices parts

Regards
Ron

It ran for about 9 months with the 2.0 head on, I think that the big end on 3 was a compound problem - it wasnt knocking particularly badly, but tolerances are SO tight with the B20 head on that even a slight difference allowing the piston to protrude out of the block more caused the piston to strike the head.

It was literally only just though...

I'd have got away with it 100% scot free if I'd fitted the thicker head gasket available from Euro Carparts... the piston was *just* touching the head as in the engine was still running smoothly with a slight ticking noise.

All the other pistons didnt have a mark on them... it was a shame really because the car was lethally quick at that compression level, and damned good fun to drive.

The engine was still running at nearly full power the last time I took it apart - it was mis firing at idle though because the bores on three were scored with the ejected crap from the piston face and had destroyed the rings... but I couldnt face running it again when I saw how much damage there was inside and sold it to someone who had a brand new M50 motor with ~20k miles on it to transplant.

[Spice Boy]

Hmmm... Im seriously interested in this...

What are the overall benefits from fitting the B20 head? and was it a hard thing to do?

are there any drawbacks?

Im looking at turning my current car into a track car when I buy my next E34 and this is very interesting

[bmwrp8]

Yes, the B25 cams do go into the B20 head, I've done it.

However this was when I put a B20 Head on a B25 engine - the difference while it ran was amazing - engine revved a lot more freely and had a lot more power low down...

...but... the big ends went on cyl 3 and the motor self destructed :s

ahh so that's why your sig sez your experiment is dead