316i to 325i

[Bassmaster23]

Hey there guys, im interested in doing a 316i to 325i conversion, my 316i Is on a G plate, i would get a rotton 325i of similar vintage, im just wondering if its a straight engine swap or are there any mods i would have to do, i.e, do they use the same engine mounts, would i have to change the suspension, diff etc, the diff im using at the moment is off another 3 series but im not sure what one, the ratio is 3.74. Cheers! Adam.

[bimmaman]

This is the same conversion as I've had done on my car...

Depends on your budget - my budget was low, so all we swapped was the engine/gearbox... New engine mounts, new water pump, new cambelt...

A couple of brackets need to be welded in to hold the coolant reservoir, and the AFM, and thats about it!

I was already running on 325i lowering springs, so you might want to upgrade your springs/shocks...

[bimmaman]

Oh, and you'll want to upgrade your brakes to vented discs on the front, which means you'll need the bigger callipers...

[Bassmaster23]

Yeh im on a low budget too lol, does the 325i have a seperate coolant tank then? not the one thats on the side of the rad? Also do all the sensors just plug straight in? theres no major wiring to be done is there? Thanks for your reply, adam.

[Bassmaster23]

Also, does the 525i engine go straight in as there seem to be more of these for cheaper lol, thanks again, adam.

[bimmaman]

Are you talking about M50 or M20?? From your first post I assumed you meant M20...

A 525i will have an M50 afaik.

[Brianmoooore]

E34 525 can have a M20 or a M50, depending on age.
The M20 engine from a 525 is the same basic engine as that in an E30 325, but there are differences with the bits bolted on to the block.
You could use a 525 engine if you had a scrap 325 engine to rob bits off, but not really on for a 316 to 325 swap.
Re: the wiring issues. If you get a scrap 325 donor, remove the engine complete with its wiring loom. It's completely seperate from the body loom, and will plug straight into your 316, assuming both engines are facelift or pre facelift.

[SM AUTOS]

Hi,

I have just done this conversion, swapped a pre facelift 325i engine into a 91 318i.
I asked exactly the same question you just have, and nobody gave me any real answers so I was a bit in the dark

I guess you want to know exactly what you need to do it, and how to so I will tell you what I found from my experience..

1st buy a doner car. Mine was £200 for a totaly rotten chrome bumper 325. You need so many of the parts off it it's the only way to do it.

You will need to remove from the doner-

Engine (complete with everything)
Gearbox
Radiator
Exhaust
PROPSHAFT (I only found this out afterwards )
Complete engine loom (including ecu)
Front suspension legs complete with brakes
Ideally the complete rear subframe (for the diff, rear disc brakes and antiroll bar)

It is basically a "bolt in swap" however it is alot of spanner twirling stripping the doner, stripping the 316i and swapping all the bits over.
You will find you also need the expansion bottle bracket off the 325 as well as the airbox mounting bracket and lower radiator mounting brackets, however all 3 problems can be got around with a bit of jiggery pokery

As far as the wiring goes the round plug on mine did fit the round plug off the early engine loom and the car fired straight up..but I still need to sort some interior bits n peices not working (see my other post)

Is it worth it? In a word yes, it goes like poo off a blanket, sounds great, and despite what others may tell you it is fine with the original diff and drums on the rear...I couldn't get anything off the back of the 325 as it was corroded solid, having been sat on a farm for 2 years
By the time I sold 318 engine & box and some bit's & pieces off the 325i it's cost me about £150 to do the conversion.

I'm sure others on here will correct some of the things I have mentioned, but at least that gives you a good idea whats involved and I have taken the trouble to try and help which is more then anyone did for me when I asked.

Good luck if you go for it bud

[Bassmaster23]

Thanks alot steve! Most helpfull , im trying to source a rotton 325 right now :D:D

Cheers

Adam

[SM AUTOS]

No problems mate.

Just ask if you think of anything else, I will try to help if I can.