2.7 Question

[GeoffH]

Hope you guys don't mind this post as its probably all been covered but i cant find the info.

Rite, i have a H reg 320i with low miles, i also have a complete engine from a D reg 325 Sport and a 525e complete engine. My question is which is the best option with the parts i have?

Do i put the head off the 320 onto the 525e bottom end with the 325 inlet and throttle body, run it on the later loom with a later 325 ecu with a zone Chip or should i put the crank and rods from the 525e into the 325 and have the block skimmed.

What are the advantages and disadvantages of both these options or is there a better option that i havn't even thought about.

Thanks in advance
Geoff H

[fowler]

have you done a search opf the forum there is plenty of info for you

[Ant]

885 head and matching 325 pistons work as a combo

Eta pistons and the 731 head work as a combo, provided you dont mix and match the pistons shapes with the wrong combustion chamber you'll do ok either way.

885 head will net a better end result but the 731 casting is less prone to cracking through the cam journals, win some, lose some.

HTH

[fowler]

or he could build you one ^^^^^^^^^^^^^^^^^^^

[GeoffH]

Thanks for the replys, so basically either way will give me good power and torque figures. I run a garage and have built a few engines now so the putting together of the bits isn't a problem, its just all the different options people use it gets confusing. Basically in my eyes the simplest option is to just put the head onto the eta bottom end but i woud rebuild the 325 if there was massive differences in performance

I've tried doing a search for 2.7 but it bought all sorts of stuff up, i'l have to try a mre defined search if thats possible

Geoff H

[daimlerman]

I used the 525e bottom end with the 320i head,with a 325 cam and 325 inlet manifold,injectors,T/B.I added a Miller MAF and obtained 189.2BHP and a very flat torque 'curve'.If you have a look in the meets section at the Dunstable R/R day link I think I posted my graphs there.Use the loom that suits the base car.I used a zone 2.7 chip,but this had to be modified to suit the MAF.I also fitted a 3.64 diff.If your 525e head is surplus to your requirements it is worth £25 to me,£50 if it has passed a crack test.....

[fowler]

use
eta crank and block
late 325i pistons after 1988
with 885 head will need machining

[GeoffH]

fowler - Which rods would i use? what differences are there in the early and late 325 pistons and what machining would the head need? that sounds like a completely different way than ant suggests

Geoff H

[m-dtech]

Im going down the eta block and 731 head route.

using all other 325i parts afm and intake etc.

[fowler]

email him and he will tell you
you can throught 731 head on on the eta bottom end it will give a nice torquey 2,7

[GeoffH]

Thanks for the replys, i need to build the engine and get it installed over the winter with very little spare time and many other projects so think i'l try and put the 320 head onto the eta bottom end and see how it fairs, whats the difference between the 320 head and the 525e head then

Geoff H

[m-dtech]

Thanks for the replys, i need to build the engine and get it installed over the winter with very little spare time and many other projects so think i'l try and put the 320 head onto the eta bottom end and see how it fairs, whats the difference between the 320 head and the 525e head then

Geoff H

I believe the valves and ports are smaller and the CR is different.

[StuBeeDoo]

Thanks for the replys, i need to build the engine and get it installed over the winter with very little spare time and many other projects so think i'l try and put the 320 head onto the eta bottom end and see how it fairs, whats the difference between the 320 head and the 525e head then

Geoff H

I believe the valves and ports are smaller and the CR is different.

.... And the cam only runs in 4 journals. It's an attempt to reduce friction and therefore assist in increasing fuel economy. It's a no-no for a normal revving engine - the camshaft will be in danger of flexing at high revs and ultimately breaking.

[GeoffH]

Thanks for all the replys but one thing i'm still struggling to get my head round is what is the advantage of using the 325 parts and skimming the block etc over just putting a 320 head onto an eta bottom end

Sorry if i seem thick

Geoff H

[StuBeeDoo]

Thanks for all the replys but one thing i'm still struggling to get my head round is what is the advantage of using the 325 parts and skimming the block etc over just putting a 320 head onto an eta bottom end

Sorry if i seem thick

Geoff H

There are 3 ways of doing a 2.7 Geoff
320i/323i 'head straight on the eta bottom end, as you suggest. - Should give a genuine 180 bhp.
325i 'head straight on the eta. Probably 190bhp if you're lucky. The 'head and pistons aren't really matched, but you'll have enough compression to in the eta block to compensate.
325i pistons on 320i/323i rods and 325i 'head. Requires the block decked and a vernier cam wheel. The best option for really big power, but expensive in machining and additional parts.

Of course, there's always the 2.8. That doesn't need the machining or the cam wheel. Crankshafts aren't that easy to come by though.
HTH
Stuart.

[GeoffH]

so what advantage do i get from the 325 head, could i not just port the 320 head to the same shape ports as the 325 and if possible fit 325 valves (question i will be asking later) it will cost me £80 to have my block decked and £45 to have my early 325 piston skirts machined so not stupid money but in all honesty i'm not going to throw big money at this engine by the means of cam and pistons etc so is there any advantage to me from the 325 rouute over putting the head on the eta bottom end, anythin has gota be quicker than my 320

Geoff H

[StuBeeDoo]

Sorry Geoff, can I bring this down to a personal level? (I think we could both be on a similar wavelength here)
If I were going to build an engine simply because I wasn't happy with the performance of the 320i (I have plans, but it's not a 2.7 - and that's another story), I'd go for the 320i/323i 'head straight on the eta bottom end. I wouldn't even bother porting it or putting the bigger valves in it.
The theory is this.....
Porting and bigger valves are both the sort of work you do for top end gains. For mid-range, the ports and valves don't want to be any bigger than necessary. Mid-range is where it's at for day-to-day driving. You want the engine to be as "flexible" as possible. Why sacrifice a bit of your new-found torque for a little more top-end that you'll rarely - if ever - use?
It's known that the standard 320i/323i head is capable of flowing enough to make 200bhp in a 2.7 with the right cam and chip.
If it were me, I'd do as above with 325i TB on a 320i manifold and a mild chip from Ant. Theoretically, that will give the strongest mid-range, and consequently make the best daily-driver.
HTH
Stuart.

[GeoffH]

Thanks for that, you seem to have hit the nail on the had with what i want out of the engine and the car, i have a nova that is my toy and my E30 is my baby but it is used every day for every day duties so i'm never going to throw huge amounts of money at it i just want it to be quicker as i'm fed up wit the slow and thursty 320, think its my low milage head onto my eta bottom end way of thinking after your advece

Geoff H

[m-dtech]

im going for a usable 200bhp target as i want to use it on knockhill and the midrange torque is the reason im using 2.0 head.

[Andyboy]

You CAN fit an 885 325i head to a standard Eta short engine with Eta pistons. I've done it, and it works. The compression ratio works out at around 9.3:1. It gives plenty of power and absolutely no issues at all.

Fitting 325i pistons means stripping the whole engine, skimming the block and buying a vernier wheel to re-time the camshaft, plus pulling apart a good (?) 325i engine. Sod that. Let everyone else chase bhp figures, you just build a decent powerful engine for a few quid. Ignore all the bullshit about how the compression ratio will be too low etc etc etc.

If the 325i Sport engine is good, I would just drop that in. It will be so much more powerful than a 320i and with the 4.1 diff it will be pretty quick. Swap over the 320i engine loom and use the 320i ECU whilst you hunt down a later 325i ECU.

[m-dtech]

You CAN fit an 885 325i head to a standard Eta short engine with Eta pistons. I've done it, and it works. The compression ratio works out at around 9.3:1. It gives plenty of power and absolutely no issues at all.

Fitting 325i pistons means stripping the whole engine, skimming the block and buying a vernier wheel to re-time the camshaft, plus pulling apart a good (?) 325i engine. Sod that. Let everyone else chase bhp figures, you just build a decent powerful engine for a few quid. Ignore all the bullshit about how the compression ratio will be too low etc etc etc.

If the 325i Sport engine is good, I would just drop that in. It will be so much more powerful than a 320i and with the 4.1 diff it will be pretty quick. Swap over the 320i engine loom and use the 320i ECU whilst you hunt down a later 325i ECU.

what would be better andy ?

the 325i head or the 320i 731 head?

what would the C/R ratio be with the 731 2.0 head ??

[Andyboy]

what would the C/R ratio be with the 731 2.0 head ??

The same as a 525e - the 731 head has the same valves and chamber volume, so 10.2:1.

[Jhonno]

stick the 325i head on the eta bottom end imo..as andyboy says, it works, tho the piston shape and the chamber volume arent ideally matched it does the job and has the better flowing head/camcombo

[GeoffH]

I'm all confused now, can i not put 325 pistons onto the eta rods and build it in the eta bottom end and put the 325 head on, if putting the 320 head on keeps the same compression ratio how come it produces so much mor power and torque that with the eta head

Geoff H

[m-dtech]

I'm all confused now, can i not put 325 pistons onto the eta rods and build it in the eta bottom end and put the 325 head on, if putting the 320 head on keeps the same compression ratio how come it produces so much mor power and torque that with the eta head

Geoff H

the eta head and the 320i head are the same i think, apart from the camshaft jornals. (early 200 casting and latter 731 casting)

the eta head is not designed to rev above 4.5k

you essentialy are removing the rev limiter when you use a 2.7 chip on the eta conversion.

[GeoffH]

so why not just chip up the standard eta lump

[m-dtech]

so why not just chip up the standard eta lump

im only guessing, but its something to do with oil starvation in the head and camshaft.

basicaly the engine wont last long !

[StuBeeDoo]

can i not put 325 pistons onto the eta rods

You'll need to deck the block - the height of the 325i pistons from the gudgeon pin to the top of the crown is different.
eta crank and rods with 325i pistons leaves the piston too far down the bore - which is why the block has to be decked.
Using the 325i rods pushes the piston 3mm too far up the bore. Ideally what is needed is 132mm rods. 320i/323i/eta rods are 130mm and 325i ones are 135mm.

[Onz]

Hi Guys,

really interesting thread, I was just considering what has been said here. I know that Alpina did something similar but apparently added the diesel crank aswel. Just out of interest what combination did they use?


O

[StuBeeDoo]

I know that Alpina did something similar but apparently added the diesel crank aswel. Just out of interest what combination did they use?

324td crank, 320i/323i rods and custom pistons, IIRC. Simon13 (and a few others) will know exactly.

[StuBeeDoo]

so why not just chip up the standard eta lump

AFAIK, it's because the head doesn't flow enough for high revs, and the 4-bearing cam won't take the revs, if you could succeed in getting them up. I'm not sure about the injectors, but if they're unique, they may not have the flow capability either.

[ed325i]

Its less work to build a 2.8 than a 2.7

[daimlerman]

For a budget built 2.7,see my post at the start of this thread.My only 'luxury extra' is the Miller MAF.Do not forget that you will need a 2.7 chip for your ECU.Ant will sell you this.

[Weeden]

Hi i am now running a 323 head with 325 inlet and 525e bottem end. And trust me you wont be dissaponted with it (it flies) .

[Ant]

Alpina used TD crank, 325i rods ( @ 135mm ) and specially made versions of the M20B25 pistons with the wrist pin moved to allow the whole lot to run in a stock M20 @ 206mm deck height.

320/323 head with Eta bottom end is the cheapest method, and it does the job well enough for the £Â£ outlaid

!