m20b20 head on an eta?

[wolverine_sr24]

my car is a 1986 325e 2.7 eta..

so if i'm correct, the M20B20 is a 731 head correct? which means it'll fit on the M20B27 motor right?

the dude claims its a real euro motor that came out of a touring, hes going to take pics of the casting number and will let me know.

My questions: will it be a straight swap? will it produce a significant amount of HP?

My co worker said that on the pre 88 etas cant straight swap a 885 i head and that the 731 is my best answer. is that true? I will be stroking this car in the long run, but if I have the opportunity to get the head right now I mind as well just do it.

THANK YOU!

[digger]

It's a straight swap, should add some horsepowers but it's Impossible to make something worse than an eta so....

Reality is in stock format that 731 isn't miles ahead of the eta head so don't be expecting 200hp

[wolverine_sr24]

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

[jeffnhiscars]

731 came off a b23. I'm not so sure about the b20 but I'm doubtful. Bed check the casting number

[Hooffenstein HD]

731 came off a b23. I'm not so sure about the b20 but I'm doubtful. Bed check the casting number

B20 had 731. Late model (motronic) B20 even have dual valve springs.

[wolverine_sr24]

he said its a touring, so im guessing its a late model? is there any difference from having single or double valve springs?

[wolverine_sr24]

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?

[digger]

youre just using the b20 head right? not the block or pistons?

[wolverine_sr24]

correct, just right now im only using the head..

later on next year ill be stroking it with pistons, rods, blah blah blah

so will it work?

[digger]

you dont want to use the b20 block or pistons for anything, use the b27 block in the car.

when you say stroking what crank, rods and pistons?

[wolverine_sr24]

so yes with the head?

maybe the b 25 rods and pistons I saw a thread where a guy was comparing the b23 and b25 cam and supposedly there is no difference. however I havent put that into thought yet, maybe the 545ti? i have to see what goes best and is compatible with the 2.7 build , and I saw your m20b31 build (beautiful<3) and i might go with custom pistons, unsure yet.

[digger]

so yes with the head?

maybe the b 25 rods and pistons I saw a thread where a guy was comparing the b23 and b25 cam and supposedly there is no difference. however I havent put that into thought yet, maybe the 545ti? i have to see what goes best and is compatible with the 2.7 build , and I saw your m20b31 build (beautiful<3) and i might go with custom pistons, unsure yet.

the head is fine to use, it works on both 80 and 84mm bores

the b20 pistons/block are 80mm so you would not want them. some people in the UK bore them to 84mm but i personally would just use a b25/b27 block.

only thing you don't do is use b25 style pistons and the 200 or 731 head it causes interference

[Kershaw]

I know for a fact I cant get 200 hp unless I do a turbo on a m20..

No, you can get 300whp out of an m20 naturally aspirated. Just not very streetable.

[wolverine_sr24]

the head is fine to use, it works on both 80 and 84mm bores

the b20 pistons/block are 80mm so you would not want them. some people in the UK bore them to 84mm but i personally would just use a b25/b27 block.

only thing you don't do is use b25 style pistons and the 200 or 731 head it causes interference

I found an I head for 100, so I think Im just going to swap my head for an 885!

[wolverine_sr24]

No, you can get 300whp out of an m20 naturally aspirated. Just not very streetable.

thats if you go full custom work on everything right? I seen some people's build and they are INSANE. where they mod the injectors to shoot to the ports and polishing heads, going super crazy. and they are barely getting up to 230s