'84 325e 2.7i swap questions

[Varinn]

Hey, I've got an early model eta with a leaking cam seal right now and in the process of fixing it I'm considering doing the conversion to an i head.

I've been offered a low mileage 323i head and 325i intake, electronics, etc from a friend for dirt cheap.
My engine is an '84 2.7 in good mechanical condition
The head is from an '81 323i, I would likely do a refresh before install
The rest of the parts are coming from an '88 325is with a running donor engine

As far as I've heard I'll be needing to grab the intake, injectors, dme, harnesses and obviously the head. What am I missing?? I'd assume that a pressure test would be money well spent, as well as the obvious head gasket, bolts, intake gaskets etc.

I have all tools, access to a hoist and a group of friends that are BMW techs (and the source of the parts), all I need is confirmation on the required bits to convert.

[dirty thirty]

Throttle body, crank sensor, trigger wheel and I think some people use the I cooling system.

[The Humjet]

The 81' 323i head is basically the same head casting as yours. It will allow the 2.7 to rev more due to hotter cam, more cam bearings and better oiling but it won't flow much better since valves and ports are same size.
Try and get a 325i head. Or e30 323i or 320i head.

[Varinn]

Hmmm, didnt realize there was a difference between e30 and e21 323i heads. So the e21 would more so allow me an extension of rpm's, rather than an actual power increase?

[The Humjet]

You would get more power. But it will be still fairly restricted, but more can be made.
Cast 200 head is what's found on e30 325e and e21 323i.
Cast 731 is what was found on e30 320i and 323i. They had a similar casting to the 200 but with larger ports.
Cast 885 is found on e30 325i they hard a further increase in port size and larger valves. But a drop in the compression ratio. Good for turbos but not so much for NA.
There has always been a debate whether to go for the 731 head or 885 head. But there is only a few HP in between them at the end of the day.

[Varinn]

Will the standard 173(?) dme run all forms of the conversion? I'd assume with such a large change in flow rates and the obious 2L displacement change between the 2.5 and 2.7's that major gains can be had with a custom tune.

I'm also curious if the 325i exhaust is needed, with the 325e having a single pipe stock, the step to the twin might gain large amounts by evening out the intake and exhaust flow

[The Humjet]

You would have to get a chip. You could get an Alpina c27 chip from eBay for cheap. You may also need larger 19# injectors.
I'm using a miller Maf and w.a.r chip on my conversion.
The eta exhaust would also be restrictive. I'm gonna be running a set of headers into y pipe turning into a single 2.5" system with hi flow cat, a muffler and resonator. I'd put that last on your list just get it running right first and then start doing performance bits later.

[Varinn]

Random update, I've picked up a 3.25LSD to run in the ETA for the time being. I went down to my buddies today to order up new bushings, gaskets, oil etc. While I was at the shop today I was offered a complete m20b25 with a rebuilt head out of a rear ended car for $200, the engine runs great. Included with the deal would be all components of the motor and harnesses/ecu. It's a known car to my friends, and verified to be well maintained.

Engine is an out of an 87 325ic

Does this sound like a reasonable deal? In terms of effort it is vastly less work than doing the 327i conversion, a straight swap could be done in a day. How does the 325i compare to the 325e as a daily driver/autocross car, and I've seen most recommendations be that it is best suited with a 3.93 or 4.10 differential. Is the torque curve so far different that it makes that much difference?

[The Humjet]

I say why not that's exactly what I'm doing I found a cheap m20b25 out of an e34 525i and all I did was swap the 2.5 block to the 2.7 block out of my 86 eta. Kept the 2.5 harness sensors and cyl head.
That way you get the torque from the eta and the power from the 2.5 which is good for autocrossing.
Most guys recommend the 3.73 diff.

[Varinn]

I was thinking more along the lines of a straight swap to the m20b25, no other mods save for a chip and possibly exhaust seeing as it wont come with the motor anyways.

EDIT: i may consider using a MarkD chip tuned for 19# injectors as well as throwing in a cam while the motor's on a stand. What sort of benefits would this offer?

[The Humjet]

Fair enough but since you have an eta block already you might as well attach it to the m20b25 while its on the stand. Because you're gonna have to open the motor to replace stuff like gaskets, timing belt and water pump anyway. That's just my 2c.
Mark D probably makes one of the best chips out there, I bought a W.A.R chip and Maf only cause I found it cheap and I could ditch the AFM.
I wouldnt bother with a cam they cost too much for the gains they give but they do sound good when at idle. Unless your running high comp then it won't do much to the performance it'll just shift the powerband upwards.

[ForcedFirebird]

You would get more power. But it will be still fairly restricted, but more can be made.
Cast 200 head is what's found on e30 325e and e21 323i.
Cast 731 is what was found on e30 320i and 323i. They had a similar casting to the 200 but with larger ports.
Cast 885 is found on e30 325i they hard a further increase in port size and larger valves. But a drop in the compression ratio. Good for turbos but not so much for NA.
There has always been a debate whether to go for the 731 head or 885 head. But there is only a few HP in between them at the end of the day.

My 885/eta combination made more power and TQ at the wheels than a friend's stock i with similar mileage, even though it had the single eta exhaust. You lose .4:1 compression but gain displacement so it's almost a wash.

[The Humjet]

I love how people say its drop in cr is so bad that power levals are the same between a 327i and 325i. What a load of crap.

[Varinn]

My 885/eta combination made more power and TQ at the wheels than a friend's stock i with similar mileage, even though it had the single eta exhaust. You lose .4:1 compression but gain displacement so it's almost a wash.

Hmmm, is that a super eta block or an early eta?? I hear so many "dude the car will barely run" claims that it would be nice to know it will work using an early eta with an 885 head. I have a choice right now between a 200 casting 323i head and an 885. The 323i setup would cost roughly $100 more than using the 885. I'm going to be picking up a complete 87 325i motor as a starting point

[Varinn]

Also, what possible gains in CR can be had by shaving the head or using a thinner HG?