1979 BMW E21 3 Series - S54 Project

As a fellow S54 owner I am interested to see how this gets along .

I would love to do something similar...there is an old 320 down the road tucked away behind this guys house......

JP

So we’ve seen the car briefly, now let’s take a look at the engine.

Back when I bought this I was planning to do a full rebuild with lightweight pistons and cams etc, nearly 2 years on I think I’ll be throwing it back together to standard spec (340hp will be plenty in an E21). Since I planned to rebuild anyway I bought a cheap complete engine with a rattle – suspected vanos issue. Here it is dragged into the back garden:




I soon set about stripping it down to look for the cause of the rattle







Nowt wrong with the top end, and the vanos pistons were nice and rattle free (I rebuilt them anyway). Keep on digging…






Hmmm that could be it! #4 big end bearing completely shot, along with the crank journal and con rod… I set about ordering the parts required needed but then everything got boxed up so I could move house, which is sort of where this project stalled.

More catching up now, this time the gearbox!

Now, obviously the E21 drivetrain won't be able to handle nearly 3x the original power output, so will need to be replaced. There are a few options, the best probably being the ZF 5 speed found in E36 328 tourings, E46 328 and 330s. Its more than strong enough and just about fits in the E21 tunnel. But the more I thought about it, the more I wanted the 6 speed gearbox! The only thing putting me off was the price, then I happened upon an E36 M3 Evo SMG gearbox for just £70!!

The SMG system is a bit strange, in that is uses the same Getrag 6 speed gearbox as the manual cars, but controlled by an ECU. Because the gear linkage is controlled by a computer, the SMG boxes don't have any of the pins and springs that give the gear linkage 'feel' and layout the 'H' pattern that you feel when changing gears. To convert an SMG box to manual, you simply need to add these pins and springs. One way of doing this is to take the SMG bellhousing and machine the holes needed for the pins and add them this way, alternately you find a scrap manual gearbox and swap the bellhousings over! Eventually I found a scrap E46 M3 manual gearbox and set about swapping the bell housing to my good, 60K mile SMG box:



Here is the 2 bell housings side by side, can you spot the difference?


This is a closeup of the SMG, notice the cast lumps? On the manual this is where the shift pins sit


Here is the manual, see the addition of a bearing to the arm, and 2 pins in the casting? this is what gives resistance as you move the gear stick left - right, along with the spring.


Another advantage of the E36 evo gearbox is it uses a 10 spline input shaft which is shared with loads of other BMWs, whereas the E46 uses an 11 spline input shaft and is the only car in BMWs range to do so. This basically means I can use clutch kits and flywheels for M50/52/54/S50 cars, which tend to be cheaper than E46 parts.

E36 10 spline:


E46 11 spline:


Sorry for all the words and boring pictures, but i love all this nerdy technical stuff :lol:

I promise the next update will be more interesting!!

This is a great project! I just sold my S38B38 powered E28..

I thought I was bad, my car knowledge is more general and not as detailed.

Can't say it often helps in pub quizzes.

Excellent. I had an m3 with the s54 it is quite an engine, I really want one stuffed in a Capri.

Please keep the tech stuff coming. I really enjoy it (for some unknown reason).

At least now when, inevitably, the question "Which is the only BMW with an 11 spline gearbox?" comes up down the Ex-pat's Arms Quiz'n'Bingo night, I'll be right in there.

Never been a big BMW fan but I've bookmarked this one.

Likewise. Though (while I love them both duly separated) pubs and quizzes are not meant to be conjoined in any way imho!

Cheers

Matt