WTD: TBMW 2.7 conversion article

[antony 0]

hey.

A while ago someone had posted an article from Total BMW on the 2.7ltr conversion, using the 731 head.

(I've got the one about using the 325i head)

Have searched, but can't find it anywhere. So if anyone has it, could they please re-post it, or email it to me at [email protected]

cheers

antony.

[bravo 35]

I found it. But only because I remember that Gus posted it and called it rebuild, not conversion.

[antony 0]

sweet.

Am considering doing this in the near future.

[bravo 35]

Several of us have looked into it. Usually the conversations go like this:

Unless you are rebuilding the m20 anyway, you are better off doing an m50 swap.

If you are going to do an m50 swap, for the little bit extra you are better off doing an m52b28 swap. Or looking at FI on your m20 which you are rebuilding anyway.

But all that said, it's probably still not a bad way to go.

[martyyn 2]

So what were the reasons for doing a swap rather than going the 2.7 route ?

[antony 0]

And most conversions normally go like this:

for a lil' bit extra, but then for a lil' bit extra, then for a lil' bit extra..... :o

I'm just after simple and cheap (both don't really exist), but the 2.7ltr with a 731 head seems to be the way to go, i was considering for a while the 2.8, but then you get the above....just a lil' bit extra (plus it's not that tried and tested as the 2.7)

I'm just starting to collect parts now, so I wouldn't expect anything for a while (I'm not known for my speed when it comes to getting things done lol)

[bravo 35]

Yeah all good, just passing on the comments made as a culmination of many hours of discussion amongst alot of people both on and off this forum.

Martyn - power bang for buck is the reason. Look at the HP and torque figures for m20b25, m20b27, m50b25, m52b28, and compare the various costs of doing each and you'll soon see why.

But I guess like anthony says, it can always just escalate and escalate.

Becasue even if you go down the FI route (probably best bang for buck) not only do you spend alot doing it, but then you make enough power that you have to upgrade brakes etc also which adds to cost again.

[bravo 35]

repost

Edited September 1, 2007 by bravo

[Gus 5]

yep. the 731 head and 2.7 bottom end way to guy..nice n cheap (basically a head rebuild)..if you whack a decent lumpy cam in there should be around 190hp is with some decent torque....great street car. one day i might even do it just for fun.

[martyyn 2]

I'm just after simple and cheap (both don't really exist), but the 2.7ltr with a 731 head seems to be the way to go, i was considering for a while the 2.8, but then you get the above....just a lil' bit extra (plus it's not that tried and tested as the 2.7)

My understanding is that the 2.8 is just doing exactly the same as the 2.7 but using a 2.8 crank from a 328,528 or even a 728 (IIRC) for example. You need a small bit manufactured on the end of the crank but thats it.

Bravo, I was hoping for a bit more of an explanation my friend. What sort of costs are we talking about for a 2.7 convertion in NZ compared to swapping in another engine ?

Everything Ive seen of a 2.7 convertion suggests that its relatively easy, relatively cheap (in the UK where the parts are plentyfull - so perhaps that gives it a head start) and ends up giving you a very good street car.

190bhp is not difficult to get with a chip and a cam (although Im happy to be corrected) and 210 is what you could easily expect from a 2.7 perhaps a little more with a 2.8 with the all important torque rising quite a bit.

[phil millar 0]

Hi guys,i don't think that you can do this ,the 731 head valves will meet the top of the 2.7 pistons,if this was the case you could put a 731 head on a 325i block (don't think so)this question has been asked before on this forum.Correct me if i'm wrong but do it factually.Thanks.

[antony 0]

you can do this.

731 heads do not match with a 325i block tho. this is why if you do this conversion with a 325i head, you also need to replace the pistons (which are shorter, therefore meaning you need to shave the block 2-3mm.)

Which is why I am using the 731 head to avoid the work mentioned above, although i will be using a 325i inlet manifold, injectors, AFM, (and the FPR if there any different).

Edited September 2, 2007 by antony

[Andrew 30]

Yes you can do anything -

No you don't need any modification to fit an M5x crank in (I'm using a 3.2 S50 one) - Obviously you will need custom pistons.

I think the 2.7 swap is a waste of time - it barely makes anymore power than the 2.5

[antony 0]

well I've got a 320i, so don't see reason not to go to 2.7.

look at it this way, if i didn't go to 2.7 i would go m20b25, not m50 or any other sort of conversion.

Ill be looking for 190 - 200hp, with a cam and chip.

[martyyn 2]

Doing a 2.7 properly will easily see 200bhp over the standard 170bhp. But the big gain is torque.

Going the 2.8 route would give closer to 210-215bhp with torque rising to somewhere around 210 ! Thats a considerable amount more than a standard 167 is it not ?

Its a relatively easy 'bolt on' job and the parts (I imagine) arent that hard to come by, so rather than saying 'just because' why do you guys think its a waste of time ?

[Gus 5]

this has been done a million times...basically the 731 head way is nice easy and cheap as it is just a headgasket and head rebuild..any other stroker way is going to involve rebuilding the bottom end...great if your planning on doing it anyway or need to, but with that sort of money better engines (such as the m50/52) start coming into play

the way antony wants to do it is best, using 325i manifold n stuff and the eta bottom and 731 in terms of cost/performance IMO...the other ways are better performance but cost a lot more

[BM WORLD 1285]

a freind of mine is doing one soon , he has a 323i(same head as 2L) hartge head and exhaust headers ,and a 525e engine block .

fitting into a 89 fl 325ia with cooked engine , black with black leather recaro's . hartge rear spoiler , hartge 16" wheels ,(and looking for hartge or other body kit to fit to it ) going to use all the ecu ,loom , inlet manifold etc from 325i but with 2.3 head on the 2.7 block .

should go well and a manual conversion kit fitted at the same time .

Edited September 3, 2007 by Brent HARTGE535i

[Andrew 30]

Going the 2.8 route would give closer to 210-215bhp with torque rising to somewhere around 210 ! Thats a considerable amount more than a standard 167 is it not ?

So i assume you are guessing engine horsepowers. The english mags all appear to be totally wrong when "guessing" in their 2.7 articles.

Those gains are unrealistic. I have yet to see one that actually makes that power (because people never do the required work to the head). Best ones I've seen are the Alpina 2.7s - and they make about 10 - 13 more kW than a good cond 2.5.

The different between 2.5 and 2.7 on the road or racetrack is so negligible it isn't worth doing.

I'm only hoping to get 230 ish (170 kw) at the wheels with a 3.1 ltr and heeaaapsss of headwork + hardcore exhaust + intake with a link ECU.

[martyyn 2]

I have yet to see one that actually makes that power (because people never do the required work to the head).

Ahhh but thats why I said 'if you do it properly'. Im not talking about just sticking bits in and hoping for the best.

Do we so many n00bs on here now wanting to slam and turbo 316's that thats the assumption we make when someone talks about doing this sort of thing ?

I'm only hoping to get 230 ish (170 kw) at the wheels with a 3.1 ltr and heeaaapsss of headwork + hardcore exhaust + intake with a link ECU.

Which is the way it should be done and the numbers you have sound pretty good to me. When you start with a standard 325 doing 170 (if your lucky) I wouldve though getting 230 was quite substantial rather than 'only'.

Oh and Ive seen dyno's of good 2.7's getting 210 but they have had the work done properly so perhaps the magazines are correct after all.

[Andrew 30]

Ahhh but thats why I said 'if you do it properly'. Im not talking about just sticking bits in and hoping for the best.

Do we so many n00bs on here now wanting to slam and turbo 316's that thats the assumption we make when someone talks about doing this sort of thing ?

Which is the way it should be done and the numbers you have sound pretty good to me. When you start with a standard 325 doing 170 (if your lucky) I wouldve though getting 230 was quite substantial rather than 'only'.

Oh and Ive seen dyno's of good 2.7's getting 210 but they have had the work done properly so perhaps the magazines are correct after all.

To clear things up - a stock 325 sees roughly 130 hp on a dyno - I'm expecting 100 hp more with my setup.

There is no way a 2.7 would whack out 210 at the wheels.

But no body DOES the head job (it's a couple of grand of work by itself, and makes all the difference.)

[Nic325i 0]

To clear things up - a stock 325 sees roughly 130 hp on a dyno - I'm expecting 100 hp more with my setup.

There is no way a 2.7 would whack out 210 at the wheels.

But no body DOES the head job (it's a couple of grand of work by itself, and makes all the difference.)

The claims on (for example) E30zone tend to be 200-220hp at the crank, with most being at the lower end of that spectrum - i.e. similar to what was claimed by Alpina/Hartge back in the day

[Gus 5]

the UK guys seem to measure SAE corrected..ie an approximation of flywheel horsepower. pretty useless but good for comparing HP cock lengths.

i wouldnt discount the 2.7 if you want to keep it relatively original with some more torque and a 'factoryish' conversion, but dont go expected lots of power unless you are prepared to spend the $$. look at andys setup..will be badass, but not exactly cheap..only makes sense if you do it in stages or are keeping within a series rules

[gmccormack 0]

If you push a 2.5L engine out to 2.7L you have only created a 8% increase in capacity, assuming no other mods and realising HP per cc drops as capacity increases then some of the 2.7 conversion claims seam pretty unrealistic. An extra 200cc just aren't going to make another 40-50hp