BMW Repair: Engine swap, asking the right questions, engine swaps

Question
Josh - What if I use just the head from the 525i engine on the 325e engine? Do I have issues with intake and exhaust manifolds and fuel injection stuff? The only reason I keep mentioning the 525i engine is because I can buy it for $500. The owner says it ran perfectly prior to being wrecked so I thought I could buy it and use the parts to have a cool little 325i with a 2.7L block and head from an "i". What are thoughts on this?
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Followup To

Question -
Josh - I have a 1987 325e that needs some head work and I'm sorting through a few different options before I get started. #1 - I have an option to purchase the engine from a wrecked 1990 525i. Will I be able to put that engine in my 1987 E30 chassis? If so, will it be a even swap or will I have track down a bunch of 325i parts and pieces to make it work? For instance, are the intake and exhaust manifolds the same? What about the ECU?  #2 - Re-work the head on the existing "e" and call it a day? Thanks for your expert advice.

Answer -
Rick,
 Well technically you "can" drop the 325i engine in, but you are in for a large headache.  Honestly you would be better off to just go buy a 325i.
 
 Your asking the right questions too, as the wiring harness, ECU, and various other electronics are different between the two cars.  You will have to put a new wiring harness in (Pain in the neck), buy an "i" ECU that matches the wiring harness for sensors.  And by getting an ECU, you will probably have to buy a used one, and you dont know how it's been treated/stored...

 You are definately better off doing your #2 option.  it will be a direct bolt on replacement (Plug and play), and much less time consuming.  The only reason I could see doing the first option, is if you lived on an island and there were no other BMW's around!

 I have been in your shoes, and done many engine swaps with these cars.  It's not worth it unless you are building a race car, and have unlimited time/money.

 If you have any other questions please let me know.

 Thanks,
 Josh

Answer
Rick,
 Putting the "i" head on the "e" block is a hot-button issue with many E30 owners.  I have done it, and I wasn't really impressed.  The problem you have, is that you are putting an "i" head into an "e" car.  The "i" engine is meant to spin to 6500 rpm, while the "e" engine only spins to 4750.  If you put the "i" head into a car with "e" electronics, you will only spin the "i" head to 4750rpm, and it will be a waste.  That's only the tip of iceberg too.  The "e" pistons have a dished center, while "i" pistons have a raised "pop-up" piston.  The combustion chambers are designed to work with one type of piston, and if you put an "i" head on and "e" block you are lowering compression. (larger combustion chamber + dished piston).  The main issue is that you still have "e" electronics, which will have a rev limit of 4750, so you wont be able to make any power with the "i" head, and it will probably be slower.
 Now if you had an "i" car, and put the "e" block (pistons, con-rods, crank) in place of the "i" block, then it would work (I have this setup), but the compression loss really makes the engine perform how it did before.  There have been countless tries to make this engine work, and produce power above the standard 325i, and the only way to do it is to buy custom pistons ($$$).  

  The only thing you can really do is to put the "i" cam in the "e" head, and put a chip in the ECU to raise the rev limit.  You will keep good compression, while adding a little hotter cam.  This might cause idle issues though, as the "i" cam's have alot more lift than the "e" cam.

 Honestly, unless you are willing to spend alot of money, it's not worth it to jeopardize the drivability of the car.  I had an 84 325e that had 325k miles on it, and I liked that car better than any I've owned since.  The "e" motor may not make as much HP as the 325i, but it makes more torque, which is what you feel anyways.  I dont drive at Peak HP everywhere I go, but I do use the abundant torque of the E motor.  A key phrase from the 1950's will sum it up
 "Speed cost's money.... how fast do you wanna go?"
 Josh