2.0 - 2.7 conversion

[e30bmlover]

hi all, iv decided to give the 320 a bit more poke. i have £700 to play with. i want to do a 2.7 conversion, iv made my mind up!
can someone please tell me (in plain english) what i need.
320 head(check)
525e bottom end(not got yet)
what exhaust and manifold? what ecu? will the obc still work? do i keep the 320 cam? what about the throttle body and afm and throttle position swich?i want to give the 2.7 as much power as possible(keeping within my budget)
any help will be greatly appreciated!!!!!!

[Brianmoooore]

First of all, this conversion won't give your 320 a bit more poke - it'll give it a LOT more poke.
The cheap 2.7 route uses the 320 head. There is a better and much more expensive route which needs a 325 head and things machined.
For the cheap route you just stick a 320 head on a 2.7 bottom end with sump from the 320 if neccessary.
Use the inlet manifold and TB from a 325, and the complete motronic engine electrics set up from either the 320 or a 325, fitting a 2.7 zone chip into the ECU.
OBC will still work, as will the "check" system if you have one, as long as you use a sump with the oil level sensor.
I think the 325 is the preferred OE cam, but I've never been able to find a completely definative answer on this.
You should be able to do all this including reconning most of the bits in your budget.

[e30bmlover]

a 2.7 bottom end? do u mean 525e bottom end? (2.7 lump with an economy head) ???? will i need to have the 320 head bored out to take the 525e pistons? thanks tim

[joe-320i]

I WANT BIGGER TOO

[Brianmoooore]

a 2.7 bottom end? do u mean 525e bottom end? (2.7 lump with an economy head) ???? will i need to have the 320 head bored out to take the 525e pistons? thanks tim

Yes, 525e bottom end. 320 head fits straight on with no issues at all.
525e, IIRC, were all autos, so don't forget to stick a spigot bearing in the end of the crank

[e30bmlover]

will need to get hold of a 325i injector rail and afm?

[julianm40]

Sounds exactly like the sort of thing I need to do! Is it a piece o' piss?

[Templ8e30]

will need to get hold of a 325i injector rail and afm?

Yes you'll need the 325i injectors complete with fuel pressure regulator, the afm is also needed. The 325i inlet manifold with the throtlle body is much better than the 320i unit.

A 325i cam is a better bet than the mild 320i cam.

The 320i exhaust manifold is the same as the 325i.

A 325i exhaust is better than the 320i.

Get a 2.7 zone chip off Ant and fit it to your ECU ( assuming it has a green Bosch sticker and the number ends in 172).

Job's a good un.

Cheers,

Iain T

[blingsta]

i would advise against a 2.0 head as the ports are small and will need to be ported to a bigger size, just slap the 2.5 head which will again go straight on! im in process of doing this conversion myself but using a shrichk 272 cam instead of the standard 325 cam

[Templ8e30]

i would advise against a 2.0 head as the ports are small and will need to be ported to a bigger size, just slap the 2.5 head which will again go straight on! im in process of doing this conversion myself but using a shrichk 272 cam instead of the standard 325 cam

The 320i ports (731 head casting) are no smaller than the 325i ports, the valves are 2mm smaller though.

Cheers,

Iain T

[blingsta]

so why does everyone advise the 320 head rather than the 325? my mechanic says the 325 head goes straight onto the eta block, surely that would make more sense than making the valve seats bigger on the 320 head?

[Templ8e30]

so why does everyone advise the 320 head rather than the 325? my mechanic says the 325 head goes straight onto the eta block, surely that would make more sense than making the valve seats bigger on the 320 head?

Because the 320i head has the correct shape and volume combustion chambers for the 525e pistons.

The 325i uses a different shape of piston with a combustion chamber to match, fitting the 325i head will work but you'll get a lower compression ratio for starters.

Also the 325i head is known for cracking whilst the 320i isn't.

Cheers,

Iain t

[jonbuoy]

so why does everyone advise the 320 head rather than the 325? my mechanic says the 325 head goes straight onto the eta block, surely that would make more sense than making the valve seats bigger on the 320 head?

Because the 320i head has the correct shape and volume combustion chambers for the 525e pistons.

The 325i uses a different shape of piston with a combustion chamber to match, fitting the 325i head will work but you'll get a lower compression ratio for starters.

Also the 325i head is known for cracking whilst the 320i isn't.

Cheers,

Iain t

I was told that you can get away with using the 323i head without the worrie's of using a 2.5 head. I know Dips is doing this conversion but what is your opinion?

[Templ8e30]

I was told that you can get away with using the 323i head without the worrie's of using a 2.5 head. I know Dips is doing this conversion but what is your opinion?

The E30 323i head is the same as the 320i head just not as many of them about !

Cheers,

Iain T

[beardymat]

hey iain

just pulled the etta engine from my trollop today along with a few other nik naks

im still not 100% which way to go as regards to 731 head on etta bottom end or etta crank n rods into my 89 325 engine with the necessary decked block

heard you can get better results from the later/harder path and with it being a later engine it seems you dont have to modify the piston skirts????

what would you do given that i have a 320 which i can pull the head off and a good lowish mile 325 (85000) in my sport?dont mind it being dearer for more ponies

p.s. you goin to ferrybridge next weekend,would like to chat in more detail

[blingsta]

i know its been covered in previous posts and i spent 2hrs reading them all, but still not sure what to do!, firstly, is lowering the compression by using 325 head a bad thing?? or do i stick with using the 320 head and keep compression high but port the valve seats so it excepts 325 valves as they are bigger?????? That is all i need to know.. pls pls help

[bottlecapE30]

go with the 320 head and fit the 325 bits the low compression is just to low....i think like 7.5:1? to low unless you will use boost

[Simon13]

the valves being 2mm smaller than a 2.5 head will make a massive difference top end as the engine just can't breathe well enough. Yes 320 head 2.7's make good low down torque but they are crap everywhere else

Contary to popular belief u can fit a 325i head onto an Eta bottom end, use 325i inlet manifold,AFM and ECU. The peron who did this and has it running calculated the compression ratio to around 9.5:1 iirc.

If all this is true then u would be a fool to use a 320 head!

[bottlecapE30]

You will only have a higher 9.5:1 ratio if you use a super ETA bottom end post '88 if you get a pre '88 bottom end you will need diferent pistons trust me i made this mistake

[blingsta]

i think ive made up my mind guys.. im going for 320 head with 325 valves and 325 everything else... whatever the out come, im sure it will be faster than a 325i !!

[WerkdE30]

im planing to do this to my 320i. only problem is i figure if im gonna use the 320 head to save cash. ill hafto get the bigger valves n if im already payn for that might aswell go sum even bigger valves. does anyone know where u would find these? and maybe stronger valve springs? are these items rediculously priced?

hopefully someone here likes to do things excessively like me and will have all the info....

[bottlecapE30]

In the states Kormanfastbmw.com has alsorts of valve options many that are hard to find now.(email for a up to date price sheet) If you do go to a larger valve i think you will have to enlarge the seat in the head for them to make any difference

[Chaos]

Contary to popular belief u can fit a 325i head onto an Eta bottom end, use 325i inlet manifold,AFM and ECU. The peron who did this and has it running calculated the compression ratio to around 9.5:1 iirc.

If all this is true then u would be a fool to use a 320 head!

simon is correct.
i believe andy everett has done this conversion using an 885 (2.5 head) with no machining etc needed as has at least one guy on the 5 series forum.


the myth of having to use a 2.0 head comes form america where the specs of the various cars and engines involved are very different.

[bottlecapE30]

i keep forgeting that you guys don't have the same eta's as we do in the states

[Templ8e30]

The myth of having to use a 2.0 head comes form america where the specs of the various cars and engines involved are very different.

I doubt that as the yanks don't have the 320i.

WerkdE30 [im planing to do this to my 320i. only problem is i figure if im gonna use the 320 head to save cash. ill hafto get the bigger valves n if im already payn for that might aswell go sum even bigger valves. does anyone know where u would find these? and maybe stronger valve springs? are these items rediculously priced?]

Don't use bigger valves than the 325i as the pistons will have to be machined, the valve pockets won't be big enough !. The standard 320i/325i valve springs are strong enough as-is unles you go for a wild high lift cam as well. I'd get valves from your local engine builder, he'll probably do them at trade price if he's fitting the larger seats for them anyway.

Beardymat, To be honest mate if you have the time and patience I'd go the whole hog and do the 2.5-2.7 route rather than the 2.0-2.7 and get better results.

Cheers,

Iain T

[Martinaston]

Do you need a chip if your using the standard cam

[Jhonno]

to get the best from it yes

you've got an extra 200cc!! Makes a big difference to fueling needs imo

this should be sticky!! (not that it'd stop ppl asking again and again )

[bottlecapE30]

Argos from what you said this swap differs very much from UK models to US models

[blingsta]

Argos, thanx for all your info, you've just made me change my mind again! i was thinking of using 320 head and porting it all just so i can keep compression up, but im gona take your advice and just use 325 head with shrickh 272 cam

[Chaos]

*** blatant plug ***

im currently selling a perfectly running 525e with plenty of history if anyone wants an engine for a conversion.

[Palazzo]

OK, I've read everything I can, done searches and have a spare 325i motor. Am I right in thinking that I use:

325i block/head/throttle body/pistons
eta crank and conrods
Skim block to suit (1.5-2mm)
Spigot bearing on crank for manual box
Preferably a better cam for best result

Every post seems to have different ideas, but this should work shouldn't it? Have a 325is and a 325i cab to drop end result into.

Cheers.

[Project_E30]

Argos from what you said this swap differs very much from UK models to US models

It will be in the US because

a) The US Eta is low compression (well, 9:1)

b) You don't have any 731 head castings over there.

You need to be talking to JonB here on the Zone to get some 731 heads crated over to the States. You'd need the complete head with cam and inlet manifold as a bolt on power increase. You'd go from 129 to 170 bhp instantly.

As for chips, you will ALWAYS need one. It's not just about fuelling (btw you will need a set of 325i injectors with a 2.7 - 2 litre ones aren't good enough). The other big thing is ignition timing. Don't forget that when you increase the stroke of an engine, the piston speeds increase also and going from a 2 litre to a 2.7 is a massive jump in terms of ignition timing.

In other words:

at 5000 rpm the piston speed of a 2 litre is about 36 ft per sec. A 2.7 is around 44 feet per sec so you can see how the ignition advance in a 2 litre ECU is going to be totally wrong for a 2.7! Just upping the fuelling is not enough and it needs to be spot on. Too little advance and it'll just feel flat, too much low speed advance and the crank will rumble like buggery and eventually hole a piston.

I'm trying to get a copy made of an old AMD chip that was custom made on a dyno for an original C2 2.7 Alpina.

So just to confirm. If we go the 731 head route the only thing me need to change regarding timing would be to get a suitable chip fitted to the ECU? Maybe the one from the zone shop?

Other than that we can use all the mechanicals from a 525e bottom end and a 731 cast head and suitable e30 sump.


Cheers

[Brianmoooore]

[
So just to confirm. If we go the 731 head route the only thing me need to change regarding timing would be to get a suitable chip fitted to the ECU? Maybe the one from the zone shop?

Other than that we can use all the mechanicals from a 525e bottom end and a 731 cast head and suitable e30 sump.


Cheers

Correct! This is the cheap, easy, quick 2.7 conversion that can be done in a few hours. 2.7 zone chip is the one for the job.