The damp in the old garage had had an insidious impact on the car in the years it had stood there while I was busy with the house restoration, although all the work I had done on the body in 2002 was pretty well protected from the inside with Waxoyl and on the underside with Tectyl. The engine compartment, though, had suffered quite badly and there were signs of mould and surface rust everywhere. The wiring loom was covered, as was normal back in the eighties, with a cotton based tape which had just disintegrated in places and it fell apart when moved. Any aluminium parts had also become badly oxidated and even the interior leather had patches of mildew. The only option was to pull the engine and transmission, remove anything else that was easily removable and repair, restore or replace as necessary. The following slideshow covers the period between May 2010 to the end of that year. After stripping everything down and creating a pretty long list of parts necessary I got it priced up at the BMW dealers. It was going to cost around €1800 just from them with a lot of other stuff on top of that, with a bit of discount as a long standing customer it came out at just under €1500 for the oem parts. So I started with other work through the winter of 2010/11 whilst trying to save some money for the parts I needed.
Following the strip down there followed a period of clean and repair of the engine compartment. There was no serious rust anywhere, just patches of surface rust which I power brushed away (Dremel) and treated with anti corrosion solution (just in case) followed by primer and colour using an air brush. Certain aluminium parts like the ABS brake module had developed some deposits which needed to be painstakingly cleaned away and that cost a lot of time with a tooth brush. The subframe was removed and treated to a coating to protect it for the future and various other parts like the power steering fluid reservoir and various brackets were also treated to a new coat of paint after blasting in my small blast cabinet. The headlight pods were also blasted and painted and the headlamp wiper motors needed to be completely restored due to being seized up. The wiring loom was also completely stripped of the old tape, recovered and fixed in place starting at the bulkhead, this alone took a couple of evenings to complete. The insulating foam on the underside of the hood was in a bad state, it was full of 20+ years of dirt and dust and was also starting to disintegrate. After cleaning up the paintwork in the same way as the engine compartment I replaced the insulating foam with some non-oem stuff purchased at Conrad Electronics. This had a nice smooth shiny surface which will be easier to keep clean and a pack sufficient for the hood cost €20, which is considerably less than the $80+ as listed on the realoem.com site for the original parts.
Once the parts for the engine rebuild arrived the serious work of rebuilding the engine could take place. During the strip down I had measured all moving parts like valves to check that they were within tolerances. Although in pretty good condition with no wear on the crank bearing surfaces I opted to replace the main and big-end bearing shells. The cylinder walls were checked for any out of round or other wear from top to bottom of the bore with a telescopic internal bore gauge and were found to be well within tolerances and in pretty amazing condition considering the fairly high mileage (285k Km.) of the car. After cleaning the block (inside and out) the bores were honed out to remove the glaze that builds up from the process of igniting the fuel. This polished surface has to be removed because it inhibits the oil from forming a good seal between the rings and bore. The process of honing restores a cross hatch pattern of extremely fine scratches which then hold a thin film of oil to create the compression necessary for complete combustion. It also removes the lip of glazing which builds up at the very top of the bores. I built a home made jig to suspend a simple power drill from a sort of gimbal. This held a simple 3 bladed cylinder hone controlled by a variable foot pedal much like a sewing machine. This gave me the extra hand necessary to add some diesel fuel as lubricant while the other hand lifted the whole jig up and down and the foot controlled the speed of the drill. New rings were used and the compression when finished was back to where it should be. After cleaning again and painting, the block was turned upside down to fit the main bearing shells followed by the cleaned and polished crankshaft. The next check was the bearing clearances which I did by using Plastigauge. This is a thin strip of plasticene like material which, when compressed by the bearing cap, flattens to a width which can be measured by comparing it to a supplied chart which tells you the clearance. BMW only supplies two bearing shell sizes for these old engines, the blue set and the red set. In the past there more size variations available but these have been discontinued. Through using a combination of red in the block and blue in the main cap the correct tolerance was achieved.
The lateral play of the valves in the cylinder head was well within tolerance so the head was disassembled and all parts were kept in sets marked so that they can be reassembled in the original positions in the head. The head was sent to be skimmed to remove any deposits and get it absolutely flat to ensure good fitting with the head gasket. I had built a jig to compress the valve springs to be able to get the cam in and out without damaging anything, I’ll probably do a separate section in the workshop section to describe this but in short it cost me about €30 in steel stock and fasteners to build. the original BMW tool (if you can find one on eBay or something) will cost you a few hundred dollars. The dealers don’t lend out tools, even obsolete ones. The valves were pretty coked up so they were cleaned a polished in my lathe, then they were lapped in by hand in the original valve guide position. After cleaning again the valves were reassembled with the original springs which were well within tolerance with respect to height. The cam was also in really good condition so it was reused. I had considered a cam with a larger dwell but decided against it after reading some technical advice on the internet (see what Fritz has to say about tuning the M30). The rest of the rebuild was pretty straight forward, replacing parts where necessary. All the aluminium timing chain cover parts together with the valve cover and various other bits were blasted and powder coated gloss black. The coating on the ribs and BMW emblem on the valve cover was later carefully scraped away and the aluminium was buffed up to a good shine. Last photo is of the engine block ready for installation.
The next stage was to re-install the engine and transmission. I have no photo’s of the engine between removing it from the engine stand and installing it in the engine bay as I had my hands full :-). Basically the car was rolled from the workshop, the block was then hung from the hoist in the workshop, removed from the stand and lowered to a static support from where the clutch was fitted. Next the transmission was reinstalled and the complete assembly raised to clear the nose of the car. The car was rolled back into the workshop and the engine and transmission were manoeuvred into place in the engine bay using the same load leveller shown in one of the photo’s of the Mustang restoration. To be honest I could have used some help at this stage but eventually it was sitting on it’s engine mounts and after jacking the car up again the gearbox rear support was re-fitted. In the previous months I had found time to modify the gear stick and linkage to create a short shift system. Unfortunately no photo’s of this but the technique is well known, commercial kits are also available ready to just drop in. The top of the stick (in the car) is shortened, the part protruding under the tunnel is lengthened and the linkage to the box has to be slightly modified to clear the balance disc at the front of the prop shaft. I turned some new bushes for the linkage from some Delrin rod, inserted a new oem plastic bearing for the shift rod itself and when finished it felt a lot more tight and direct than before the strip-down. I had to fit a complete new prop-shaft assembly because the u-joints had dried out and are not serviceable (no grease nipples). By now it was May 2012 and I was itching to get back on the road.
Unfortunately there was quite a bit more work to do.