320 head on 325i?

[kevo]

hi all, i was just wondering as people put the 320i head on eta 2.7 conversions, what would happen if you put a 320 head on a 325i? would it work or be useless? reason being is i'm after more torque from my low comp 325 lump and am either going to stick high comp pistons in or try and find a 2.7 and currently have a complete running 320 lump in the garage.
cheers
kev

[daimlerman]

Interesting idea...

Main snag is the 325 pistons that are shaped to suit the shape of the 325i(885 casting)cylinder head.

True enough that 320i(731 casting)heads are used with 2.7,this is the head that I use,but with stock eta pistons,which have a similar,flat top design to 320i items.

If you are desperate enough to try this,may I suggest that you sit the head on the block,fit and tension a belt,then turn the engine by hand with no head bolts in and see if the valves clear?

[DmcL]

there was a thread about stroker builds on e30tech with some dyno graphs for differeny head/piston combos and the 731 head with 2.7 bottom always seems to make less HP than a standard 325i, makes a little more torque tho. only 2.7 stroker worth doing going by the dyno graphs posted would be an 885 head with 2.7 bottom end and M20B25 pistons to match the 885 heads shape. everything else posted made less HP than a standard 325i.

[eta]

Well my 2.7 with an 885 head + eta pistons + 325i exhaust manifold + Fritz exhaust makes 137 whp/175fhp@ 5900 rpm. The dyno showed less but when I calculate (sorry a spreadsheet does the donkey work) the acceleration (accounting for everything), with the dyno's wheel number, I find the numbers have to be 11% higher to get the acceleration I actually measure. So that combo is just as good as the a 2.7i built with a 320i head. If fact daimlermans engine I think is a bit stronger.

Agreed though using 325i pistons would be better.