Swap M20B27 for M20B25

[nefarious7907]

Is it worth it to swap a ETA motor for an I motor or just go with the M50?

[MR 325]

Swapping an Eta motor for an i motor is usually a really cheap and easy to gain almost 50 horse.

Josh [Eurospeed88] did this on his old car.

[e30bimmerdude]

??? why dont you go head and build your eta..and make it faster than an 'I'.. thats what im doing...i much rather keep my motor and put on the 325i head or in my case the 323i head and make it a 2.7i or in my case i dont know what it would be called with the 323i head...but just my thoughts :D

[finch]

yeah do the head conversion.
its somewhat involoved from what ive heard, but in the long run you wont be disapointed.

[nefarious7907]

I was thinking of getting the 325i motor and then putting the ETA crank in it with the eta rods, I dont want to mess with getting custom pistons or trying to find super eta pistons. I am pretty sure that it would work but I am not sure if the crank journals would clear the sides of the block. I think that this has been suggested before in another post but I cant find the post or poster.

[Switch]

i was thinking about doing the 2.8i conversion (i have a block from my old 83' 528e, and an extra "i" head in the garage.. was going to rebuild the head and block.. but i ALSO know where i can get a 323i head.. does the 323i head have larger valves? would i gain an extra advantage using it vs. the 2.5 head"?

[decay]

to put it simply, the 323i head has i-sized port passages and eta-sized valves. i plan on using i hardware to "big-valve" mine and having the head shop port around the valve area to make sure the head itself is not a restriction.

as far as the aforementioned hybrid setup, the pin-to-crown distances are different on eta and i pistons. if i weren't hung over right now i'd go look them up and do the math on whether that would make it pointlessly-low-compression or dangerously-close-to-head.