1978 BMW E12 525 (conversion to 535i Turbo)

[DMS]

Rear diff pickup points:



Penetration:


Start of the jig for the rear diff mounts (actually a replica of the original diff mount. So the diff is place at the right hight and nicely centered. Then I'll weld mounting plates for the output flanges to the steel jig. Then I'll beable to mount the E34 diff with the output flanges at the exact same location.:

[DMS]

Well my initial idea to replicate the original rear diff mount in steel so I can use it for a jig to align the output flanges didn't work out. Since the 210 diff is so much bigger that this diff mount is in the way. Actually most of the chassis beam above the diff needs to be cut out. So I ditched that idea and the only other solution I could think off was to cut two holes in the trunk floor and weld the output flange mounting plates to a temporary beam fixed in the trunk.

Yesterday I took the original subframe etc off the car and mounted the modified one. I also put the 210 diff between the two output flanges and it appears these are a perfect fit. I must have been doing something right then.

So hopefully I'll have time tonight to cut all the original beams and plates out. Then add a stronger radial beam to which I can weld the rear mounts. Next step would be to integrate this radial beam in the future cage.

Some (bad pictures):

[DMS]

Well I've found a few hours to work on it again. Cut the lateral beam out to make room for the new 2x2 inch beam. I'm constantly surprised how little rust this 35 year old car has. Ok, inside the beams there is a little fly rust and behind some hangers there is some. But it's really very solid overall.

First a test fit:


Then the rear beam removal:


There it is:


How the car stands at the moment:

[DMS]

I've been slowly booking more progress. An hour here an hour there:

I used a 50x50x2mm beam to replace the original one. Then the uprights with mounting holes for the rubber bushings I showed you before.

Started tagging the uprights in place. The passenger side beam had to little meat in the main beam to assure a strong connection. So I added small support tabs. The driver side was ok:




That left me with this:


Then added additional support for the passenger upright:


So I will relocate the petrol tank from the impact zone (trunk right behind the rear bumper) to below the passenger rear seat. While retaining the original filler location. So the filler tube will need to go through the new rear beam to be able to keep a nice down slope from the filler neck to the tank. So I needed to make a recess for this.

On the right of the rear beam:


Welded a larger diameter tube in so there is room around the new filler tube for a rubber mat. I don't want any irritating noises from the rear.










The tube in the pictures will be reshaped into the new filler tube.

The only thing left to do on the rear beam is to weld on a hanger for the rear exhaust box. I'll add the hanger when everything is in place. It'll be easier to to align everything. All contact area's are covered in zinc spray so ready for fitment.

I've fitted the exhaust tip on the rear box and cut the original recess in the back panel but I'll post pics when that's finished. Besides that I've cut a few more parts from the trunk area which need to be filled in a more convient way. I'm also thinking about shaping the trunk corners a bit different as I've alway though the E12 has a strange line here. I'll try to get some pictures to show what I mean. Current planning shows I'll be working in the trunk area for months to come. So many boring updates will be posted. No turbo action just yet. Sorry guys....

Ps. Something happend with the rotation of the pictures but you get the idea. I've way to much time to document this opposed to actual time working on stuff so it's over-documented anyway .

[tonybmw]

That will certainly be strong enough for anything

[DMS]

I didn't take any pictures but I started welding the thing in place. Damn! The first welds are looking like curse word and it's taking forever to finish it. I only got half way and there is quite a bit to learn there. I'm not used to body work so it's all quite new. Some of the problems I needed to overcome:

-The beam is 50x50x2 mm so it is quite a heat sink. I need some amperage to get good penetration while welding but the thin sheat metal of the body can not handle this. I'm burning through it. This makes butt welding difficult.
-I've applied a nice coat of 90% zinc primer on both surfaces. This makes for good rust resistance between the two surfaces which I will not be able to get to later. But it's poluting my weld puddle. Lots of splatter. I removed the layer at the places I want to weld, but this consumes a lot of time.
-Welding in awkward positions in an overhead position was new to me. I needed to speed up the feed otherwise the melted wire would just drip down on the floor or fall into the gun.

Anyway, I'm getting there. It just takes time and patience. I'll grind down what I screw-up and do it again. I'm not really worried the beam won't hold in the end. It'll be really really strong .

Ps. I ordered polyurethane exhaust rubbers for the rear box. The original rubber pieces just don't have a long life span. When these are in I can mount the rear box on it's final position. Then I know with how much I can increase the rear trunk volume. Since the original fuel tank is no longer there. The LPG tank is taking up a considerable amount of space so it's nice to get some back.