M20 eta upgrade

[Funkyasshit]

Hey!

This forum is mostly about e30 but I can't find any better place to talk about M20 than here. So I may get my hands on e28 1985 2.5 eta. I've read a lot about these 2.7 projects but none of them answers my questions, probably because most of them are about e30. 2.7 thread is nearly perfect for a start. What about head? ETA top is pretty much shit. 233 cams, bad flow etc. I'm thinking about 885 or 731 head. 885 would decrease compresion and isn't that great with ETA pistons (it's great with SETA tho). 731 head is pretty much prefect for n/a but it still is pretty far from good but it could be pretty good with all the 325i part swap but with (if i remember correctly) e23 264 camshaft.

Any help is appreciated,
cheers!

[3vilE30]

Umm, what are you asking exactly...
2.7i has been done in numerous ways goggle is your friend.

[digger]

a stock non ported 731 doesnt seem to be any better than an full 885 topend.

[Funkyasshit]

I've read all the theads I could find about 2.7i build. Some say 731 is the best, some say 885. All the parts should be fine from e30? I don't know only about front radiator. What cam 885 head has? How to calculate how thick gasket I need for head so my compression doesn't drop that much. Probably will need to get something off from head also. But if I would use 885 head I probably should use ETA crank (2.4td crank would be perfect)/rods and I/SETA (impossible to find SETA pistons) pistons but i have no idea if that combination works. I want to leave the rods from ETA to get that nice ETA torque. And could I use M50 managament with this build not Motronic 1.3? My goal probably is about 200hp. Something like 160whp?

[digger]

no matter what choice you make its going to be an average engine if its a budget build..... slap a refreshed 885 head, 1.3 electrics and I, manifolds, tb etc on a 2.7 bottom end and be done with it IMO as i dont see the 731 is worth the effort in stock form. its just not going to make power at 5k and above with a 2.7L, the power just noses over as it was designed for a 150hp 2.3L engine

if you want a budget'ish m20 the 2.8L is the way to go

[Funkyasshit]

2.8 build is way more expensive. ETA and I hybrid will not be a rocket that's for sure but 140-160whp would be pretty much perfect for a daily driver. 2.8 build is different with M50 managament, B28 crank and 2.5i late model pistons? Either way it's shitload of work if it's 2.7 or 2.8 and mpg would be over 10 l/100km. :D
Will check everything out. Maybe it will be cheaper to swap M30B34/35 than making this stroker build.

[digger]

both 2.7 options will be not far from those goals , the 731 perhaps a smidge more bottom end and the 885 a smidge more topend

[Funkyasshit]

That's the thing. With 731 build it still will have this nice bottom end but it could fall pretty bad after 5k.

[digger]

That's the thing. With 731 build it still will have this nice bottom end but it could fall pretty bad after 5k.

sounds like an eta ;)

doesn't take much effort to get the 731 flowing as good as the 885 in the right hands

[Funkyasshit]

People say 731 are better for n/a but I have no experiance in trying this. Should check things out and start putting things together to make it rev low like eta and still keep to 6k that power. After 6k I ain't aiming. I think 2.7 stroker with 731 should be fine as daily with decent MPG + some city night drift on wet/dry souldn't be a problem also. How about Motronic 1.3? Isn't it pain in the ass?