2.7 using 731 head and early 11:1 eta block

[Deano 1]

Anyone used this with success..I'm thinking the CR will be too high with stock cam.

[morerevsm3 7]

Anyone used this with success..I'm thinking the CR will be too high with stock cam.

I have a 731 head on my 85 325E, also has 325i computer and harness etc on it, seems ok with limited race track runs so far

[Deano 1]

I have a 731 head on my 85 325E, also has 325i computer and harness etc on it, seems ok with limited race track runs so far

325e is probably the 9:1 eta for the US so the 731 head will maintain that CR. The 11:1 CR eta is early Euro pre 1986 525e..putting the 731 head on will keep the 11:1 CR..is this too high?

[topcat 11]

i'd run it.

good performance upgrade.DO run the best fuel you can buy

remap?possibly

Edited June 16, 2009 by BM Weapon aka topcat

[antony 0]

I've got a 731 head on a 2.7 block. Unsure of it's year, but I was of the understanding that my compression ratio would be 10.1:1, the same as a 320i?

Compression is really good none the less, although unsure of figures.

I'm using a chip and 273/273 catcam from england.

[QuickSilver 0]

I have the early block, 11:1 CR - I'm using a 885 head though and a few other differences so its dropped a little bit, still quite high though, the 731 will keep that compression ratio just make sure that you use 98 - mine wont run happily on anything less (pinks)

Anthony, not all 320i's share the same CR, you've got the CR that your b27 originally started with, just the added benefits head and all the rest, its a good CR.

[BM WORLD 1262]

there are numbers on the block to identify which C/R pistons are fitted on the M20B27

like this

this one is from the later 10.5c/r 1987 525e

[bekker 7]

there are numbers on the block to identify which C/R pistons are fitted on the M20B27

like this

this one is from the later 10.5c/r 1987 525e

How do you interpret those numbers? I'd be keen to check mine.

[BM WORLD 1262]

How do you interpret those numbers? I'd be keen to check mine.

read this .

http://www.bimmersport.co.nz/forums/index....showtopic=23560