best mickey mouse m20?

[rede30]

There are lots of threads over the years on all these combos but of course now there is too much info and conflicting info. Just curious what people have to say currently.

I have a an eta motor sitting, an I motor sitting, and a 323i motor sitting. Will be going into a 323i. I'm thinking of just using an i motor but would there be a good combo for mixing and matching any of these heads and blocks?

[digger]

323i crank into b25 block, its 1.8mm more stroke so will likely need a slightly thicker gasket?

makes it a 2.6L, wont make a big difference but probably best bet if you want something other than a standard m20b25

[george graves]

Google for "e30 super-eta i swap". That should get you pointed on the right path. Lots of reading.

[ForcedFirebird]

325i pistons on eta rods and eta crank, shave the block 2mm and you have cheap power (~175-ish WHP)

[digger]

oh yeah, missed the part about having an eta. sell everything except m20b25 block, slugs, and eta rods and buy a m52b28 crank.....

[jeffnhiscars]

Or just put a fresh 731 head on the eta block with +2 valves and a 272 cam. Throw in itbs and headers are you are close to 200whp...but don't take my word for it

http://racehead.com.au/m20-low-compression-2-7-stroker-engine/

[digger]

there goes any sort of budget haha

[jeffnhiscars]

there goes any sort of budget haha

I'd think a head would be less than doing a mix and match long block ?

[digger]

i meant doing the whole ITB, standalone thing that is $2500-$3000 by the time you do that. For sure it gives good BFYB but it might not be what the OP is after.

however i guess it depends exactly what gets done and who does it. and how much of the while im in there, might as well do .....

[nando]

yeah, you're not getting that kind of power out of a head swap on a stock block, with stock intake, tuning, etc. You'll likely end up right around the same power as a stock M20B25.

[jeffnhiscars]

yeah, you're not getting that kind of power out of a head swap on a stock block, with stock intake, tuning, etc. You'll likely end up right around the same power as a stock M20B25.

Did you read the link ? Head alone yes although more torque than a b25 but with the other upgrades done right you should be closer to 200 I think. I'm into my 731 for about $2k including stock motronic swap parts. Itbs, headers/exhaust and standalone should probably add another $3k

Lots of options for that much I'm sure.

[digger]

Did you read the link ? Head alone yes although more torque than a b25 but with the other upgrades done right you should be closer to 200 I think. I'm into my 731 for about $2k including stock motronic swap parts. Itbs, headers/exhaust and standalone should probably add another $3k

Lots of options for that much I'm sure.

i doubt there would be much difference between a 2.7L with 731 mild ported head vs a 2.7L "i" style with stock 885 all else equal.
Rama also does a real good job with the head, if you take it to any random place the results might not be the same.

As an example about 8 or more years ago on one of the local BMW forums there was guy who swapped a 731 onto a eta bottom end, the head was ported b25 valves etc (ported to alpina spec whatever that means lol) and he gained in the vicinity of 10hp which is a bit disappointing IMO for supposedly ported head. obviously the head smoothed all over and little else


EDIT:

damn my memory is still not too bad, found the details. different dynos (and car) before and after because of an accident but it is unlikely to be that much different in outcome

stock 325e with chip




731 head ported to hartge spec. m20b25 cam, m20b23 inlet



for reference a stock m20b25 would 135-140rwhp dependent on mileage/health

power curve is alot nicer though and no apparent torque loss

[jeffnhiscars]

That bottom chart says it's a 320i, top says 325e. Are you sure they are the same car ?

Digger you and I have discussed eta options at length in various threads and the consensus (to my mind anyway) was always that the 731 would yield higher compression and over all better results in a NA install PROVIDED the head was done right.

Granted dropping a stock 731 on an eta may not be worth th trouble and for sure if you go FI the 885 is a better route. Don't make me question the effort and expense I've put in to this 731 I built with input from both you AND Rama lol

[nando]

Did you read the link ? Head alone yes although more torque than a b25 but with the other upgrades done right you should be closer to 200 I think. I'm into my 731 for about $2k including stock motronic swap parts. Itbs, headers/exhaust and standalone should probably add another $3k

Lots of options for that much I'm sure.

yes, I did, several years ago in fact. :)

sure, there's a power bump from the head swap - but I stick by you're not going to get anywhere near 200whp on an eta / 731 swap, without the ITBs, head porting, cam, larger valves, and custom tuning that engine had. Not exactly a "mickey mouse" build right? :p

[ForcedFirebird]

for reference a stock m20b25 would 135-140rwhp dependent on mileage/health

power curve is alot nicer though and no apparent torque loss

Having dyno tuned many combinations, 135-40 is pretty normal for an unmolested aged m20b25 - can almost guess based on cranking compression anymore for stock numbers lol. If the bottom end is healthy, the exhaust is opened up and accy belts off, the head is fresh, they are closer to 150-160.

m20b28, 272 cam, m52 crank, eta rods, +.5mm with stock intake and exhaust did 180whp (on Motronic with a chip, even)

Seta with 272 cam, i springs, fresh head (tired bottom end though), did 148 -but - I remember the torque being higher than power. The dyno PC crashed a while ago, lost some of my winpep files.

885 head on stock eta bottom end, 145whp (similar TQ), but when used with the eta manifold and i TB, the power only dropped 5 and it was useless after ~5500 RPM, but TQ went straight up to 170wtq!

another 885 head on eta bottom end did 138whp/150tq

Some other off the top of my head:

eta crank/rods, b25 pistons, shaved block 175whp/168tq

Fresh 885 head, RD headers, our exhaust, bottom end in good shape, 157whp/155tq(+/-tq??)

m20b28, lightly worked head, balanced aasy, all new machined surfaces etc, 272, RHD ITB's, OK headers, our exhaust, 217whp/202tq

tired bottom end (145 cranking compression with the fresh head o.0), 272 cam, RHD ITB's, light head work 180whp/170tq

stock bottom end, fresh head, 272 cam, Extrudabody ITB's, 181whp/??tq

bone stock with A/C, horrible cat back, chip only 148whp/146tq after chip only.

That bottom chart says it's a 320i, top says 325e. Are you sure they are the same car ?

Digger you and I have discussed eta options at length in various threads and the consensus (to my mind anyway) was always that the 731 would yield higher compression and over all better results in a NA install PROVIDED the head was done right.

Granted dropping a stock 731 on an eta may not be worth th trouble and for sure if you go FI the 885 is a better route. Don't make me question the effort and expense I've put in to this 731 I built with input from both you AND Rama lol

The 731 opens up the options for flat pistons (even 24v pistons on a budget), so it's easier to get higher compression slugs, don't have to worry about the head being shaved (V to P contact), and don't think they have a tendency to crack like the 885's.

As I said, you can see by the dyno numbers, an engine needs good quench. The angled band on the 885 and flat pistons kill the power for only a little gain in displacement.

OTOH, if you have a 325e, the 885 head is a nice upgrade. It's a downgrade on a 325i.