Clarifications pls: E vs I motors and swaps

[bronzit 325i]

I recently acquired an 86 325eS and I already own an 89 325i, but its dead now due to wiring.

Ive been reading around and I cant get a straight answer on which motor will give the most power. so what I need clarification on is:

Does swapping an i head on an e block actually boost hp?
Which motor (i, e, or e with i head) actually has higher compression and does that even matter?
Would I be better off dropping the entire i engine into the es or just putting the head on?

Please dont reply if you dont really know what your talking about.
for anyone interested: i had to buy the 86 because it was only $100 and it runs.

[Mike325]

You can not put the i head on an e block because the pistons are not right. Only the 88 e black can use the i head.

I believe the e has higher compression.

Drop the i engine into the e. The i has about 50 more hp.

[Stu]

You can put an 'i' head on an E block. Assuming you use the 'i' intake/TB/motronic you WILL make more power than a stock E. However, the compression does drop quite a bit. A stock E actually has a higher c/r than an I (9.2 vs 8.8 )...but due to piston/chamber design, when you put the I head on the E block, compression drops to ~8.5 or maybe lower.

[Mike325]

Ah, ok. The lower the compression means what for performance exactly though?

[Stu]

A standard E motor with an I head/intake/exh/motronic will make more power than an E motor but less than an I. I'd estimate 150hp.

[bronzit 325i]

thank you thats what i was looking for. looks like ill drop the i in not just the head... eventually....

[porsche gt1]

A standard E motor with an I head/intake/exh/motronic will make more power than an E motor but less than an I. I'd estimate 150hp.

try 127 hp with 171 tq

that is the setup that a 88e has. It also drops the compression ratio to 8.5:1.

It is a common misconception that a e with an i head gives you a lot of power.

WHAT YOU CAN DO:
if you put the I head/intake/motronic 1.1 and manifolds (intake and exhaust) you can throw a turbo on the car that will generate a lot of power. You will actually get more power than a i can get. Check www.e30tech.com as they are the kings of forced induction on a e30.

In the end if you are just looking for quick power, swap the m20b25 into your 86e and you will be a happy guy.

[porsche gt1]

Ah, ok. The lower the compression means what for performance exactly though?

gives you a slower more steady curve on a dyno, acceleration drops.

[StereoInstaller1]

try 127 hp with 171 tq

that is the setup that a 88e has.

Nope. The '88 has different pistons than any other year. That is the SETA motor. Basically, that motor has an "i" head, but an "e" cam, valve springs, intake, exhaust...but the "i" wiring, crank sensor, etc.

Easiest stroker build there is. Dual valve springs and an "i" cam, intake and headers...you is rockin' yO!

Luke

[AdamF 88iS]

The 88 E motors are different. If you put a stock I head on an early E motor you won't be happy like you would be if you did it on an 88 E motor.