m20b20 head on an eta?

[Coyote_ar]

so, my co worker said the m20b20 wont work because the bores are to small and that it has to be an b23. can anyone confirm or disagree with that?

B20 and B23 are EXACTLY the same, except for the 76.9mm stroke on the B23 vs 66mm stroke on the B20 (and the pistons to match). Both have the 81mm bore. And they even use the same 130mm conrods as the ETA.

731 head works just fine on the eta you keep the same compression ratio since the chambers have the same volume. but you need to keep the B20/B23 cam and valvetrain. You cant use the ETA cam, since it only has 4 journals and not 7 like the I cams. for Ljet cams (B23 and early B20s) you need to modify the front of the cam, to be able to fit the motronic distributor thingy. for late B20 cams thats not required since those use motronic aswell.

If you dont change the setup on your ECU, it wont work nice with the I cam, because that cam starts to wake up just when you hit the rev limiter.

If you reprogram your ECU, a 731 head will flow good enough for ~170hp. It wont be as good as a 2.7 stroker with 885 head due to the limited head flow, but still WAY better than the standard ETA.

I hope this helps you out, and let me know if you need to know anything else. good luck with your build.

[jeffnhiscars]

My b23 cam is worn out so is being replaced anyway, but this is the first time I've heard that there is a retrofit to install the b25/b27 distributor. Strictly from memory the front of the cams looks the same...just a different spacer/washer.

[wolverine_sr24]

Thanks guys, I found a b25 head for 100 and decided to just go that route, I have to find a 325i ecu and wiring. anyone know a good thread so I can learn how to wire correctly?

[Coyote_ar]

My b23 cam is worn out so is being replaced anyway, but this is the first time I've heard that there is a retrofit to install the b25/b27 distributor. Strictly from memory the front of the cams looks the same...just a different spacer/washer.

maybe there are different versions of the same cam. later B20 cams dont need it, so maybe late B23 dont either.

[JeLani]

I know for a fact I cant get 200 hp unless I do a turbo on a m20.. I heard that a 731 is a great upgrade for the eta. so i just plan to do that until i figure out what i really want to do with my eta. im leaning towards a 2.7i stroker. I seen a forum on here about a 2.9i which im going to try to achieve :D

thanks digger

Forum for a 3.1 http://www.r3vlimited.com/board/show...83#post4527083

[JeLani]

And go on www.strictlyeta.net there should be a writeup somewhere on wiring.

[Coyote_ar]

731 head needs some serious work to be able to reach 200hp.

valve size, port size, and even port shape is way superior on the 885 heads. you can still make em work, but some serious modifications are required. the good news is that theres plenty of material to work with, the water jacket is thicker than on the 885s.

[wolverine_sr24]

731 head needs some serious work to be able to reach 200hp.

valve size, port size, and even port shape is way superior on the 885 heads. you can still make em work, but some serious modifications are required. the good news is that there's plenty of material to work with, the water jacket is thicker than on the 885s.

everyone told me to get an 885 motor because I can get more power (peer pressured), so I went for it lol. I bought a super eta head (him not knowing it) for 100 bucks with only "120,000 miles". HOWEVER... when I checked it on the spot it was .007 warped in only one spot. But I checked it dirty, tomorrow ill clean it with a razor blade and check it twice. Im no mechanic I doubt it would make a difference if it was dirty or not.

but I'm hoping its still serviceable

(below is the warped area)





DIRTY LEFTOVER HEAD GASKET