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320i Cabriolet Restoration / Facelift Conversion - M50B28 Turbo

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    320i Cabriolet Restoration / Facelift Conversion - M50B28 Turbo

    Whats up guys, thought i'd get a thread up here since i started lurking the board alot. Its copied from E30 Zone so some of it may not make sense in terms of what im saying:

    Insta: @e30_cab_uk
    I've been working on this Cab at the weekends since ~March 2021. It belonged to my dad but was sat for 12 / 13 years, i asked him what he was doing with it as i was interested in a project and he said i could have it. The rear arches and rear panel were one of the biggest concerns, the arches had been repaired previously and the passenger side had a Touring Arch fitted to it. The interior was also wrecked by mice, as well as rust in lots of other typical places, this is how the car was:

    I got the car in the barn and begun the stripdown, i put in as much effort into labelling everything, jiffy bagging the bolts, taking lots of pictures etc.

    I removed the Radiator Support - it was pretty rotten and i had also planned to do the "removeable" mod to it when fitting the piece, i have the new piece but just have not worked my way round to it yet:

    Engine out and later sold on ebay for ~£150. It ran fine and sounded good, with 73k Miles on it. My plan is to go M54B30 unless i can find a reasonably priced M52B28 (Doubtful).

    Once the engine was out i noticed that the Scuttle Drain was blocked and as a result the corrosion inside the void was quite bad, i have a whole new Scuttle Panel from Cotswold and this will be getting fitted shortly.

    I also saw the corrosion around the Loom Grommet was quite bad, this was more apparent from inside the car, and as a result the passenger floor pan had a large amount of surface rust but also some bad rot in certain places.

    After the majority of the teardown was done i turned my attention to the rear of the car and its rust problem. I had always preferred Facelift cars and because of this i decided to do a Facelift conversion, i wanted to replace the entire Rear Quarters and Rear Panel. Cotswold had OEM Rear Quarters - Facelift Only (£839 for the Pair), so i ordered them and a new Facelift Rear Panel:

    I then proceeded to start cutting:

    Now a disclaimer, this is my first time doing any kind of Bodywork, Welding, Fabrication etc. I have always done mechanical work on my cars but never anything this deep, i had studied a lot of videos on do's and dont's etc. I decided to leave the Rear Panel on whilst i worked on the replacing the Inner Arch Lips and getting the Rear Quarters into place properly, so i had at least some kind of reference of where they should end up.

    There was a lot of work cutting out small sections of Rust in the Wheel Wells and where they join the sills. The passenger side also had a large amount of the inner arch already replaced, which i needed to re-do.

    The process of re-working the inner arches and lips was something that took me many many weekends, a lot of double measuring, checking fitment etc. A steep learning curve but rewarding, if i were to re-do them now, then i would probably make a slightly better job of it, i am however still pleased with the outcome i got. Its also worth mentioning that its pretty much impossible to find any Cabriolet specific Body panels, the replacement inner arch lips were advertised as Cabriolet, but when i received them it was pretty clear that they were Coupe or Touring, so i had to cut and modify these to fit.

    Unfortunately i did not get many pictures of this process as it was time consuming enough as it was, there was a lot of corrosion in the Drivers Side Inner Wheel Arch from the fuel Pipe Cover, Vapour Tank mounting points etc.

    Drivers side inner Arch & Lip done (Really sorry for the terrible pictures, just using what i have).

    I then painted and sealed the Inner Arches in a generic gun metal grey (I will be painting the car Donnington Grey)

    One of the unforeseen problems of doing an entire facelift conversion, was that the boot floor on a facelift must sit ~100mm Lower, because of this i had to create some extension pieces to bridge the gap. My welding has much improved since this.

    I began dry fitting the Rear Quarters properly and doing final / more precise cuts on the body where they would meet.

    This was quite a tedious process, especially on the end where the Quarter Panel meets with the doors, these (and most other joints) are braised from factory and it took a long time to remove the braise and tidy the joint enough so that it could be welded without contamination.

    Once i was happy i removed the rear panel and dry assembled the rear end with the boot and also the roof cover / hatch so check all the gaps. An old guy across the road gave me a tip of using self tapping screws to lock in the panels in places, this gave you a fixed position to go back to and also really helped hold the panels in place. The Panels surprisingly did not need much tweaking, though i was disappointed with the quality of the rear panel from Schmiedmann, some of its contours did not match the OEM Rear Quarters particularly well around the rear lights and will require some work with filler to make it look perfect.

    I then spent a LOT of weekends, triple checking everything, doing small bits of work i thought was easier with the panels off, before finally taking the plunge and welding the panels on - i did not braze them like from factory, i did seek advice on this and although it is not the original way of doing it, was told the risk of cracks etc were very low.

    Now that i had the Rear End back on, i wanted to get the car on a Rotisserie i bought what felt like a very very long time ago. This was from a company called Ade Foreman Light engineering, its the heaviest duty one he offers on wheels rated for ~1300kg. I braced the door shuts, boot, and front where the crossmember would have been.

    Mounted using the Bumper / Rail Positions:

    Pretty happy with the Jig, from memory it was ~£375 delivered, it has some flex when moving it around or doing pretty hard work on the car, but worth its weight in gold.

    I then wheeled the car out to the doors and used our Karcher Steam Wash to totally remove any remaining Mice leftovers, and also strip of as much wax oil and other shit from the bottom of the car / engine bay as i could:

    End Result:

    I then stripped off any of the remaining under car bits, fuel lines, brake lines etc.

    Now was the time to start the tedious process of removing all of the underseal, i got about 90% done in one day with a an angle grinder and large wire wheel, it then took about another day or two to remove all of the underseal from all the tight corners / areas. Originally i was not going to remove all of the underseal, however i am glad i did as it revealed many many places of corrosion that had not yet visibly come through the sealer. Some of these places had originated from inside the car where i can only assume heavy amounts of Mice Pee were and started corroding.

    The worst areas of rust on the underside were:

    - Rear Seat / Seatbelt Brackets.
    - Rear Tank Brackets.
    - Rear Brake Line Mounts.
    - Tube that carries Fuel Tank hoses from Filler Cap.
    - Passenger footwell areas.
    - Drivers footwell areas (both footwells were bad behind where the sliding nuts are for the gearbox).
    - Drivers side Footwell / Jacking Point / Front Arch Area where all 3 panels meet.

    These were the areas i deemed necessary of cutting out and replacing, the rest was only surface rust and i concluded it was acceptable to let Dinnitrol RC900 deal with it. Pictures in no particular order of Rust Repairs to the bottom (Yes i know my welding does not look particularly great / perfectly penetrated):

    Checking Fuel Tank Mount Positions:

    Front Sections, I had a Passenger Panel from Valcas which in the end i decided not to use. This is for sale if anyone is interested £100

    Various other bits were done and then i spent a long long time prepping the bottom to do a first coat of Dinitrol RC900, i first saw this product being used by Driftworks on their V10 E46 M3 restoration, i thought it looked really good and decided it was a good product to use in this situation.

    This was only done last weekend, and i need to do another coat, it seems to have penetrated extremely well. Slightly counter intuitive to spray on, it doesnt feel right as visually it appears to be clear coat.

    I managed to get a cheap set of E36 M3 Evo Hubs and LCA's, i also picked up a cheap Compact Rear beam, i began tearing these down and shot blasting them ready for new bearings & bushes. As of yet i am undecided on what brake setup to go with, i had done some light reading on it and though maybe i could use E46 330 brakes? Any advice on that would be great.

    I had also held off buying Balljoints for the Front Arms, i had read online about people using E30 ones instead of E36? What is the reasoning for this? Does anyone have part numbers for ones which can be used? Also which offset bushes i need for the LCA Mounts.

    I have a few questions before i start widly buying new parts:

    - Suspension bushes - this will be a road car, should i go with Powerflex "heritage" Range Poly Bushes? Or still with Lemforder bushes. I plan to use BC Coilovers with the car.
    - I plan to use E46 330, is this a compatible setup with the 5 Stud Swap Parts i have?

    I plan to buy the ~£1k ABS Mtech2 Kit posted in the General Chat section, i am pretty sure Front & Rear Bumpers will fit, as will the Door Pods, what is the recommended way to get Sideskirts on?

    Any advice, recommendations, criticism is welcomed.


    Last edited by AexD; 08-04-2022, 07:47 AM.

    Got a second coat of RC900 on at the weekend, dont think ill do anymore as it looks to have covered nicely:

    Then stripped the Drivers front Wheel Well, i repaired that hole in the bulkhead, forgot to take pictures of it after:

    I cut back the front batter tray as it was completely rotten, im moving the battery to the boot so will tidy this up and seal it before painting the engine bay:

    I then started to look at the rot around the Scuttle Drain, upon first glance it didnt look too bad, but it is quite severe, also most of the void behind the scuttle has rust to some extent, i begun to strip it but ran out of time, a job for next weekend:

    I was searching for new Rear Hub Flanges to go on the 318ti Rear Hubs, however these are actually quite expensive and are really just a solid piece, so i decided to dip mine in the Ultrasonic Bath with Rust Remover, after a Polish / Wire Wheel these should look brand new again:

    Im also planning on sending my whole interior to Lithuania, i was recommended a really good and well priced company who are on Instagram. I can get the whole interior (Apart From Dashboard) done for around ~1600 Euros (with Logistics), however i am having a really hard time finding another Drivers Rear Door Card, im not sure if this one can be repaired at all? Someone cut it to try fit speakers in:

    Not sure if anyone has advice on that?

    I also managed to find an M50B25 from an E34 which i should be paying for this week, just waiting on a video of it running and some more details first.




      Finally got a spare minute to update this, didn't get much time in Janurary to make much progress unfortunately, i'm also due to move house soon which i imagine is going to have a big impact too.

      First of all the corrosion under the scuttle panel was pretty bad as mentioned, although i'm not 100% happy with the work i did under there, i'm happy the corrosion wont return, quite simply without de-constructing the car in the reverse order to how it was constructed, its very difficult to replace every piece of corrosion with fresh metal. Cleaning, treating and sealing the corrosion still takes a very long time but you kind of feel like its a bodge at the end of it.

      I left it last weekend with a large amount of Seam Sealer curing, i've tried top layer it up so any water naturally drains towards the drain holes. I now need to paint the inside of this area before re-fitting the new Scuttle Panel.

      Whilst waiting for the Seam Sealer to dry i tackled the Front Arch Inner Lips & Engine Bay Corners. Panels from Valcas and were a great fit as per usual.

      Next on my list after re-fitting the Scuttle Panel is to fix the Chassis Loom Hole and then look to get the ABS MTech 2 kit and get the bodywork done.

      Also wrapped the interior and this is now with RESTAAuto in Lithuania. Hopefully get this back at some point soon but i'm of course in no rush, the longer it sits around the greater the chance it gets damaged. The seats will be
      Red Nappa Leather, all the Door Cards & Rear Panels Matching Red Vinyl. All the front of the interior is being Re-done in Stitched Black Vinyl. Price will be in the region of ~2500 Euros, Plus £250 Delivery each way.

      I also have a bespoke set of BC Coilovers coming, with E30 Struts, E36 M3 Mountings on the Front and E36 Compact Mountings on the Rear.

      Still waiting on my M50B25 to be removed and shipped. Again not an item im currently in a rush for.




        I've not had much chance to work on the car lately, been pretty manic at the weekends, going to try start working on it in the evenings as the days get longer.

        Painted inside the scuttle panel area, and the back of the scuttle panel:

        Mocked up and clamped the scuttle panel:

        Welded in place:

        I also corrected a bit of rust on the hole where the passenger door loom plug sits, it was fairly tedious / an odd shape and i forgot to take pictures of it, but with that done it marks the end of the cutting & welding on the car - i only need to re-fit the front crossmember / radiator support when i get the car off the jig, this will be getting bolted anyway.

        I now actually need to sit down and think about the order in which things need to be done in order to start re-assembling the car. I want to get it back on its wheels ASAP, which means finishing the bottom as far as possible, Seam Sealing, Undersealing, running fuel / brake lines etc.

        I started seam sealing the underside, ended up using much more than anticipated, i think partly due to filling the rear arch lips completely with sealer to stop dirt sitting in there, i need to go back over it all again for a second coat as it looks to dry quite think (Dinitrol Brand).

        RESTAAuto has also started on my interior, i asked him to send me lots of pictures, which he has been doing. He found a very good match in nappa leather to match the Red Vinyl he typically uses, though this wont arrive to him for 3 - 4 weeks yet. The door cards are done in Vinyl, i think they look very good personally. I was weary how well the same material would last on seats, hence going for leather instead. Very impressed with them so far, great communication and look to be doing a very good job.

        Im going to collect my M50b25 this weekend, its from an E34 so has the correct sump etc. I have a build worked out (copying a friends), it will end up being built as an M50b30 Turbo, his has done a drift season @ just over 550bhp so it should be good for a road / occasional track car.




          A bit more progress this weekend, unfortunately i forgot about replacing the fuel filler pipe bracket, which was rotten previously. i had to create a basic bracket for this.

          Whilst i was in there i also remembered that, most of the threaded studs which are used to hold the breather pipe cover were also gone, only one was remaining. I decided to Rivnut these instead of trying to put studs back in.

          I also added two extra ones where the cover meets the pipe that goes through the interior:

          I had to modify the cover plate to add two tabs to allow me to bolt down that end of the pipe (it didnt fit very well to be honest, its a genuine part and cost ~£95 but probably i didnt replace the pipe in the exact same location it came from).


          Modified and everything mock fitted:

          I also prepped the front wheel arches and engine bay for painting in RC900 this weekend, no interesting pics of that unfortunately.

          Im also building a 1500 x 600 x 600 shot blasting cabinet so that i can shotblast the subframes, rear arms etc. i should hopefully have that finished by the weekend.

          Im also working on a 3D Printed Loom Grommet that can be clamped round the existing loom and bolted to the bulkhead, ill get some pictures of that once its a bit further along.



            Some pictures of the 3D Scan of my Rear Door Card, i can now design a Speaker / Grille Cover that will fit the look of the interior better, hoping to use traditional Black Speaker Mesh or a Nice Fabric Cover - still undecided atm, i will probably do some 3D Renders.

            I think the scan came out really well, hopefully get the files sometime this week, i will make the files available too. The company is called Laminar Solutions, it cost ~£70 for the scan which is small price to pay in my opinion for being able to accurately model off an object without having to try take measurements of an organic shape.

            I also managed to find a M50B25 Non-Vanos engine for my build. Previously i had one organised, i drove 3.5 Hours only to get there and find out the guy had an M60 sat there waiting for me? So 7 hours of driving wasted but at least now i finally have one coming which should be here today. Pics to follow.



              Engine Arrived. Going to steam wash it off and then put it away until i start piecing together the internals for it.

              More Interior Progress Pics

              Here is my idea of the Body Loom Grommet, it can be bolted around the existing loom, with 4 Seals inside, and then bolted to the bulkhead after. Need to do a prototype and go from there.



                Small Update, been spending what little time i have after work getting the shotblasting cabinet finished, its 95% there now. Decent volume chamber so i can crack on with painting all of the suspension & subframe components, i can even fit a fuel tank in here if i want.

                Prototype Grommet came out ok, i actually made it much smaller than originally planned, looks like its going to work perfectly fine and fit in the location nicely.

                Finished welding, prepping the engine bay and front arches, then a few coats of RC900 totally finishes the underside of the car, i also prepped what was left of rust in the interior and RC900'd all of that as well. I also did in all the cavities related to the car being a cabrio and as much of the chassis internally as possible. This should hopefully put a stopper in any other surface rust that was out of sight, all these cavities will of course have Dinitrol Cavity Wax applied as well further aiding rust prevention.

                Finished Seam sealing as well, engine bay is complete - i just need to seam seal a few areas in the interior, inside the inner rear quarter panels and in the boot. I've probably gone through 6 or 7 tins of seam sealer but the car is fully sealed, more so than factory.

                I'm now prepping to get the car undersealed, im just wracking my brains and trying to think of anything else that should be done before that. Once i have the car undersealed im going to probably try and run fuel & brake lines.

                Once thats done, im going to blast & paint the entire suspension assemblies, get it on and try to get it back on the floor. Im hoping i should be able to move fairly quickly now, most of the tedious work is done (in theory) now i just need to spend a bunch of money on new parts and get it back together.

                Couple more interior pics, he now has the leather to do the seats so its nearing completion:

                Few more interior pics, my dash was not cracked but the material was faded, worn.



                  So a bit more progress.

                  I started looking into PTFE Braided Fuel and brake lines, i decided it was going to be difficult to accommodate these using the OEM Line Mounts, also the Self Tapping studs in the body were half rotten, so i decided to grind these flat and replace them with M4 Rivet Nuts. Ill draw up some bespoke mounts in Solidworks to 3D Print once i know the diameter of the lines and it will be easy to fix them to the body this way:

                  I also re-fitted the Drain plugs under the front seats:

                  With this done i masked all the necessary places, filled in all of the rivet nuts and finally undersealed the car. Its still pretty wet in the pictures and has dried to a slighty more matte finish which is nice, i hate the look of a car that has been heavily waxoiled and is shiny etc. Also i masked the areas as best i could by the pictures i took previously, i might have to re-visit this briefly when i start bolting stuff back on to get it exactly right but using the gun is very easy and its such a basic job to do:


                    RESTAuto has also received the leather for the seats and started to work on them, im honestly amazed at how good the finish of the leather is, super excited now to see them in real life. He's also replaced the heating elements with a newer modern system, replaced any struts that have failed etc.

                    Was also really impressed with how he repaired this mouse hole, registered well with my OCD:

                    Colour match against the vinyl used on the door cards.

                    Next im going to be prepping and painting the suspension components and subframes, i ordered the reinforcement kits for all the items so will need to weld these on, shot blast and then paint.




                      A bit of progress this weekend, my life feels like a shit show at the moment, barely have any time to work on the car and when i do i keep forgetting to take any pictures.

                      This weekend i welded on all of my Trailing Arm & Subframe Reinforcement Plates, i only got a couple of pictures but will get the rest up soon.

                      Rear Trailing Arms:

                      Unfortunatley, my front subframe had already bent where the engine mounts bolt to, and stupid me i only noticed this AFTER welding the plates to the other side. With a bit of heat, clamps & hammer I managed to get it back to within 2mm of the other side (The "ok" side, im guessing it was "ok", was ~28mm from the table to the plate. The other side was almost 40mm from the table to the plate).

                      I then took all the parts back to work to give them a second round through the shot blaster, i had missed a few bits on most of the parts and also there was some flash rusting occurring where i had to leave them a week since last blasting them. I managed to get a coat of paint on the front & rear arms, hoping to get the rest done this weekend.

                      Think i finalized my rear speaker pod design, i think this fits well with the rest of the car but gives me the extra depth i need, looks better etc.

                      3D Render:

                      Test Print:




                        Ok so a small update.

                        Finally got round to painting the bits i had shotblasted beore. I actually had to re-shotblast them since welding on the reinforcement plates as they had flash rusted a little. In the end i used the 2 Part Epoxy Mastic from It seems to be really solid stuff and was easy to spray on. Its also already survived a few knocks and bangs from when pressing the new bearings in the hubs etc.

                        Got to try out the new paint 'booth' at work (its not really a booth more of just an extraction wall).

                        I also ordered a full E30 & M50 Bolt Kit. Really happy i did this, they are all labelled and packaged individually, and will save a massive amount of time sorting, cleaning and sending my existing ones for plating.

                        New Dust Shield and Bearings fitted to rear arms.

                        Same for the Fronts.

                        I ordered polybushes a while back but some were out of stock, but they should finally be here tomorrow.

                        I am now expecting my completion date on my house move to be this month (June) so with that i will officially be broke for a while. I can still carry on doing some bodywork and other restoration of metal covers etc until i am back on my feet a bit.

                        Im hoping to get it back on the floor in the next month or two, then order the ABS Mtech2 kit etc.




                          Ok so a small update, i stripped the diff, blasted the casing and flanges and painted them. I Glass Bead blasted the Rear Case which cleaned up nicely, not the same finish as Wet Vapour Blasting but still much better than before.

                          Just need to get the uprated Clutch Pack and re-assemble it (sounds simple...).

                          Due to be buying Fuel & Brake Lines soon as well as the Coilovers, so hopefully get the car back on the floor soon'ish.



                            So my bits came in from Racing Diffs for the diff rebuild, i also got the oil, O Rings etc so im prepping to re-assemble it this weekend. Took a little while to finish stripping the diff completely of its bearings etc. I also had any of the bits i didn't paint Zinc Plated, as well as some other random bits i wanted to test it out on. I prefer the silver finish as opposed to the yellowed variant.

                            The new clutch pack from Racing Diffs has an extra plate to help with performance a bit so it has 3 clutch plates now as opposed to 2.

                            Excuse the messy bench, thats all my bro's shit.

                            I also pulled the engine off the racking at work and took it down to the barn, i partially stripped it and gave it a quick once over, its not frozen and appears to turn over quite freely - which is good news as it was purchased as condition unknown.

                            Im still debating on what sort of build to do with it. My original plan was to do the typical 2.8 Vanos Stroker build which consists of:

                            - Modifying the Head for VANOS.
                            - Moving the Inlet Cams to the Exhaust Side (requires some modification).
                            - M54b30 Exhaust Cams on the Inlet (requires some Modification).
                            - M52b28 Forged Crank.
                            - Forged Rods & Pistons.
                            - 84.5mm Overbore -
                            This gives the engine a Square Setup - 84.5mm Stroke & 84.5mm Bore which is supposed to be healthy in terms of harmonics etc.

                            However its fairly costly and is maybe way way overkill for my power goals of ~500hp. There is also a debate of is running a 8.5:1 Compression ratio enjoyable on a street car in terms of engine response etc before coming into boost.

                            It looks like i could probably get away with running the engine as is (if its actually healthy) and meeting my power goals. I could Stroker & Forge it at a later date over winter.

                            I need to speak to some experts and see what the deal is tbh.

                            My house move is now confirmed for 22 August so hopefully all is well there and i can carry on spending some money on the car and get it moving forward again.