M20 "I" head Vs "E" head

[liv2race]

Hey everyone. Basicly I want to know the main differences between the two heads.

I know that the eta head has 2 less oiling holes in it for the cam. Anything else? Im mostly interested in the CC's on the combustion chamber on the two. Say I put a eta head on a otherwise stock 2.5i motor will the comp ratio change at all?

Thats the quick of it.


If your wondering why I asking read on...

My buddy had a head with a casting number that is supposed to be for a "is". I think something like 885. I dont remember.

He sent the head out for a full build.. PnP work, valvesprings etc etc. Once he got all the work done he relised that the drill holes were missing like on a eta head. Long story short he never could get any info why the casting # was IS and the features were eta.

He shelved the M20 project as he found a INSANE cheap s52 and used it. the head has been sitting for years (longbefore I had a E30) and now I have one he said he would basicly give it to me.

I come from a subaru crowed where they always made "hybrid" motors from a 2.5 block and 2.0 heads and it sucked. dont know why they did cause the combustion chamber was not made for that block and the mismatch caused all kinds of problems.

Making sure that couldent be the case if that head turns out to be a full eta head.

Thanks!

[ForcedFirebird]

I put the 885 head/cam on my 2.7, only shaved it enough to make it flat, and it runs damn good, even with the 2.93 diff and 8.3:1 compression ;)

Click the video link in my sig...

[Danny]

So many questions that have already been answered.

You can't put an e head on an I block, you'll smash your valves. I'm not sure what else you're asking really.

[liv2race]

because We dont know if it is a I or E. Ifs a fully worked head (the 2 missing holes have been drilled out by the machine shop) and Ill be adding a aftermarket cam.

getting my options. and I did search and came up with nothing on a is head missing the oil holes, or the combustion chamber CC's or anything like that.

[ForcedFirebird]

If the casting number is 885, then it's an i head, the 200 eta casting has "2.7ETA" cast right into it.

[jlevie]

I think the combustion chamber volume of both heads may be the same, but the intake and exhaust ports (and valves, I think) on an ETA head are smaller. a SuperETA head is identical to an I/IS head, with the exception of the valve springs, cam, and oil passages. In other words, an 885 head could be from a SuperETA.

[ForcedFirebird]

Chambers are not the same, if they were, then my compression wouldn't have dropped from 9.0:1 to 8.3:1 when I swapped the heads ;)

[SpecM]

the CC is smaller on a 200 (and 731) head than an 885 head. The semi-hemi pistons of a 2.5 will smash into it

but you CAN put a 885 head on a 84-87 2.7e

but it sounds like your friend might have a super-eta (1988 model 325) head, which also hass a 885 cast number. The oil passages can be easily drilled out for use on a 2.5i.

[ForcedFirebird]

Super ETA used the 885 head and had 7 cam journals, just like the "i".

The Super ETA mani was what was different, it was cast like an ETA mani, but had larger openings where it met the head.

[siggy]

My finger is in this Pie. Keeping my spare 885 head for a snapped belt rescue mission down the road. Just had a 731 head come back from the machine shop, re-surfaced, new exhaust guides & complete valve job. Someday it goes on the 86es.

Here is a picture I found somewhere, shows the intake ports on the 200/731/885 series castings. Smaller ports increase velocity..., several aspects to the port size theory.

Also using the 731 cam, said to be hotter than 885 cam. I'm expecting the 2.7 displacement, decent compression, the 731 cam and the 1.3 motronics to increase the Fun Factor on what it already a sweet daily driver.



I love the 2.7's torque that my 325i simply doesn't have. Allows for some lazy shifting around town.

[liv2race]

Thanks guys. Ill look into it more. I cant tell from the ports cause this head was already ported and polished ALOT. The oil passages have been drilled, and the valvesprings and everythign are aftermarket.

but now Im nervious. Sounds like the CC's on the chamber are the same and its the pistions on the 2.5 and 2.7 doing the compression difference. but anyway to be sure so I done kill a fresh motor?!

[SpecM]

200s and 885s do not have the same size CC.

If you have a 2.5 the only head you can use is an 885

[eta]

200 "e" heads have a combustion chamber volume of 37 CC. The 885 i head as combustion chamber volume of of 42 cc.

If your head had oil journals for the cam missing with respect to fitting a 7 bearing i cam then you must have a 200 head. The ports on the 200 head are smaller and even if they have been ported out a stock 885 head from a 325i could easily flow better. I would find a 885 head from a scrap car and bolt it on. That what I did, it works fine.

If your E30 started out with a 2.5i engine then I am not sure a simple 2.7i build using e piston is really any more powerful. They just have more low down torque but a good 2.5i will be jsut as fast if not quicker.

[liv2race]

Thanks guys. VERY informative. Thanks!!!!


More info oh the head...

I was talking to my friend again to get more info. The head was on and running for 10K on a 2.5 block.

Basicly he bought a 91 325IX. This head was on the motor from a previous "repair" before he bought the car which was running and driving.

That leads me to belive that it was a I head.

However, The head when we pulled it off had a ETA cam in it. (4 lobe I think) and no iol holes!

CANT FIGURE THIS OUT! Im going to the garage tomorrow and Im going to measure the ports and see what it comes up with.

[scottinAZ]

sounds like a super-eta head. IIRC that was an 885 head with simgle springs, 4 CAM JOURNALS DRILLED and smaller ports.