bmwe21.net forums

as mentioned on another thread i am looking for a either a 320/6 or 316 suitable for a conversion to an m20b25.
my questions could potentially be simple (hopefully) for someone who has done the conversion.

to do a decent conversion from 320/6 to m20b25 i know i am looking at:
323 calipers front and rear
323 discs and pads all around to go with 323 calipers
rear trailing arms
uprated suspension kit to 323 or aftermarket
battery in boot
poss new engine mounts?
anything else?

my next question is if i were to do a conversion from a 316 to an m20b25, what additional items to the list above would be required for the conversion. i know the 6 cylinder front subfame would need to be sourced but what else?

cheers

Check Mr Murrans thread and you'll see where he installed a 2.5. What are you doing re exhaust? A single pipe system is obviously a simpler prospect.

As far as I can see there are 3 viable options for the exhaust.
1.std 320/6 manifold and pipes so single tail pipe
2.std 323i manifold and pipes
3.custom manifold from a fabricator to couple up with whatever system I can get my hands on

I have just picked my answers up from reading topics off here tbh, thats the only experience on this subject i have as I currently don't own (or have owned) an e21. I maybe simplifying the answer to your question but it's all I know for now until I find otherwise...

if its just a road car you dont really need the expence of the 323i rear brakes. as long as the rear drums are adjusted properly and work.
i would go for the vented 323i front brakes and some good pads tho.

starting with a 4 pot m10 car would leave you needing a gearbox/prop/diff. 6 pot front anti roll bar/rear anti roll bar. (most 316s dont have a rear bar.)

Quick fire noob questions:
Can I use the box, prop and diff from a 320/6 with an m20b25?
Do 320/6 have rear anti roll bars as standard or is it just 323?
Also will the rear beam (subframe) need to be changed or is that an item that is common accross the platform range?

Yes, yes I think and unsure.

I'm sure someone who knows what they're talking about for sure will be along soon.

etchin_uk wrote:Quick fire noob questions:
Can I use the box, prop and diff from a 320/6 with an m20b25?
Do 320/6 have rear anti roll bars as standard or is it just 323?
Also will the rear beam (subframe) need to be changed or is that an item that is common accross the platform range?

From what I know from doing research for this:
- You can indeed use the box and the rest from a 320/6. I would however try to get a LSD diff if you're gonna go for big power.
- 320/6 should have a rear anti-roll bar. All models from 318i up should have one. The 323i has one mm thicker bars front and rear if I'm correct.
- The rear subframe is the same for all E21s. The trailing arms are different for a 323i, as they have brake discs.

A question though: If you don't already have an E21, why not start off with a 320/6? Would save you getting a lot of parts which can be quite expensive.
(front subframe, gbox, propsh, diff)

Thank you for the replies guys.

And yes you are right, as I dont have an e21 currently I could just get a 320/6 and save some time sourcing parts. But it's availability that's got me really, I am a victim of circumstance. I can get my hands on a cheap 320/6 with a terrible case of "tin worm" and there generally seems to be more 318's about for sale. My plan would be to do a bit of mix and match project. Parts from the 320/6 on a decent 318 shell with an m20b25 lump upfront.

Well, I know this may sound stupid but I think you may be better off saving for a 320/6. You're going to have to buy all those parts and if you're anything like me you're going to want good stuff, not just something that fits.
You're going to buy a 5-speed(sport) which are super expensive, a balanced propshaft, an LSD, better brakes. These are all super expensive.
What I'm trying to say is that if you have a 320/6 already it's just a matter of fitting the engine, and then you can part by part replace other components for better stuff. Now you're going to have to buy everything, and you'll probably end up buying the nice, expensive parts anyway.

Hope that made sense...

i started out with a 320/6 then discovered that it is basically a 316 with 2 more cylinders and is therefore imho crap i ended up buying another 323i to hoke all the bits off vented front calipers and 51mm struts, rear discback axle thicker anti roll bars. your also going to need an electrical fuel pump for the 2.5 engine which the 323i has as well as the extra hanger for the twin pipes if you want them so you would be better off saving for a 323i.