Alpina C2 2.5/2.7 question - Newbie alert!

[Sacred_Cow]

Hello - I'm a newbie on these forums so please be gentle!

I've got a question about Alpina C2 engines - how do they differ from the 2.5 M20 engines? The reason I ask is that I'm considering getting hold of an M20 2.5 to rebuild and then possibly drop into an E30 sometime next year. I'd maybe like to go down the whole Alpina replica route, right down to getting the engine right. Is it just the cams and chip, or is there more involved? I'm also curious to know how the extra size of the 2.7 litre engine is achieved on a C2 (i.e. can another block be used or is it bored out).

There's not a lot of information out there (that I've been able to find after a fair bit of searching at any rate), so if someone could point me in the right direction or could give me a few answers that would be great!

Cheers

[kam-325i]

Hi and welcome.....

I dont think that there was such thing as a "Standard" Alpina engine, as you could of just had the exhaust manifold or gone the whole hog.......

But i think most would expect to see the manifold, cam and ecu......

[Ant]

2.7 is an 84mm stroke bottom end same as B25 but with 81mm crank from TD M21 engine, 325i rods and custom Mahle or KS pistons

I have a block and pistons, all gen alpina but no crank if you wanna make a replica ? number are all there to prove provenance too btw

cam was 268/268 iirc, 6 branch very much optional it would seem, bigger bore TB on the C2 2.7, chip and porting to head with minor reshaping

HTH

[Sacred_Cow]

Thankyou for the welcome and your replies! I'm looking at getting started on it sometime next year, so I'm trying to do as much research as I can right now!

[Rosc0PColtrane]

c2.5 was cam and ecu

[daimlerman]

The joy of the Alpina cars is the special bits that Alpina built/fitted.The sorrow of these cars is the cost of replacing these parts as they break or wear out.Just as an example,most were supplied with an Alpina designed exhaust system built by Bosal(IIRC)that when available is £1300.I am given to understand that they require an order of 20 units before they will make a batch.GSF will supply an aftermarket 325 2 or 3 part system that is a bolt on replacement from about £125 to£175 ish.The 'proper' Alpina system gives a little more BHP.As Ant has mentioned, pistons were specialy cast,if available they will be very expensive.In the '80's BMW did not import deisel vehicles into the UK,so the crank from these engines is very like rocking horse poo...I wanted an Alpina as well,but as my need is for an everyday car expected to cover 300 plus miles every week and be of such a value that I could turn 'er indoors loose in it I built a budget 2.7 using a 525e engine as a base.This is a very popular conversion that gives a powerful,torque laden engine and uses the 'magic' 2.7 label.These old 525e's are now getting difficult to find in useable condition(I needed to have my crank reground) so the new 2.7 is now a 2.8, using the crank from the later engines.Have a search around in the engine conversions section for more detail. Also have a look in(I think) the photos section for Simon13 and his Alpina rebuild thread.Welcome to the zone,BTW!!

[Sacred_Cow]

Ahh thanks for the welcome and the useful information. I guess it's a matter of weighing up constructing my own 2.7 or just getting a 2.5 and completely rebuilding it and kitting it out with some goodies. The plan is to drop whatever engine I end up with into a cab at some point, although the engine is just the start, all the other stuff (retrimming, respray, suspension) I'm going to need to do my homework on. I've been running an '88 318i for a couple of years now, so I've got some idea what it will involve!

Cheers again chaps.

[Andyboy]

Alpina designed exhaust system built by Bosal(IIRC)

Boysen!

I wouldn't fit a Bosal exhaust to a ride on mower, they're shite.

Forget the TD crank and Alpina pistons, you don't need either. A 525e crank is fine along with 320i/525e rod and standard 325i pistons. You can use either the early 9.75:1 pistons or later 8.8:1 (post 9/87 plastic bumper) types but remember that the compression ratio will be higher because the 2.7 engine is compressing 33cc's more air per cylinder. Early pistons need the skirts shortening by about 10mm, not a big job for a machine shop. The block will need decking by a couple of mm to get the pistons at TDC, again cheap enough. A good head gasflowing job and a spiky cam or around 280-285 degrees will give well over 200 bhp.
All bits used are standard BMW but I'd consider using ARP rod bolts if you're giving it 6000+.

[Sacred_Cow]

I like what you're suggesting Andyboy, and I've seen the odd 525e around in the past, so it shouldn't be *too* hard to get a crank. Gasflowing, cam etc was stuff I was going to do anyway.

One question - sure to highlight my complete and utter ignorance of engine mods - will the ECU (with Alpina chip or not) adapt to the new changes especially around capacity, and if not, what will I need to do?

Sorry for repeated noob questions - I've done cars up before, just not like the mash up I intend on doing to this cab next year!

[daimlerman]

Ant will supply a chip suited to your chosen spec.Humble apoligies for the exhaust manufacturer cock-up...