After a few recent trips to quarry sprints and track days we decided that the next addition to the family would have to be something cheap, rugged, nice power and rear wheel drive. It's getting harder and harder to get get an entry on a tarmac rally these days and with plenty of quarry events and track days available it made sense to have something else to enter in the mean time with a car that didn't cost a fortune, which could be driven hard without fear of repairs costing the earth.
So the search was on for a rear wheel drive car with decent power without spending much money on engine upgrades. Pretty soon we came across a 325i BMW for little money that seemed to meet the criteria. As you can see it's not exactly how it left the factory, but looks aside the car was to prove a bargain.
When you look a little further under the skin you'll find a shell which is virtually rust free and has never met with any solid objects so no filler to be found. But the iceing on the cake was what lies under the bonnet. A sweet as a nut, 6 cylinder, 2.5 litre, 170bhp engine.
With the idea being to keep the costs to a minimum on this build the 325 engine with this power on tap as standard seemed to make a whole lot of sense.
So with the car parked up in the workshop the work began. First up was to completly strip the car to a bare shell for a good steam clean in order to start the seam welding. For anyone not familiar with seem welding , basically the car is stitch welded an inch every two inches along every major seem in the shell. Two of the main reasons for doing this job are, when the shell leaves the factory all the seems are spot welded, which is a small round weld every couple of inches and while this is perfectly strong enough for everyday use once the car is subjected to prolonged heavy competition use its not uncommon for some of these welds to break in the heavy stress points of the shell. Resulting in the worse case senario of a scrap shell. Also a car which is driven hard on tarmac with good slick tyres generates a lot of grip which in turn places a lot of stress on the shell which in turn can flex and end up altering the suspension geometry slightly. Giving the feeling of wooley or loose handling, which can be frustrating if you've spent a lot of money on uprated suspension bushes and heavy duty ball joints all round trying to eleminate play and stiffen things up. Seem welding greatly strengthens the shell and if done correctly all but rids it of any "flexing".
The shell took quite a while to strip bare as anyone who has owned a BMW will know you get a lot in there for your money.
The weight of the 3 layer carpet alone in these cars is substansial. Next up was to remove the vibration dampening felt. This can be seen in the pic on the tunnel, floors an some of the pillars. This stuff is fairly well glued in there and really requires a little heat to ease removal. Once you heat it well, it usually comes up in one peice though. A good blowtorch really helps with this job and will be essential later on when removing the seem sealer. We use these torches which are very effective and give quite a powerfull flame and the little self igniter element really comes in handy instead of having to look for a lighter each time.
Next up was removing the seam sealer around all the major seams so we could start the welding, this is quite a lot of work and takes quite a while to complete as any sealer left behind really hinders the quality of the weld. If you ever remember hearing the old saying that German cars usually don't suffer from rust, just try removing all the sealer applied by the factory and you'll quickly figure why that is. With all the sealer eventually removed it was time to get on with the welding. As you can see from the pic's there was quite a few seams to do.
The above pic's were taken after the welding and a coat of Red Oxide Primer applied. The actuall welds were a little hard to see so I've highlighted them with a blue mark. It's important to get a heavy coat of good rust preventitive primer over the bare metal welds as soon as possible to stop any rust forming. The pic below is taken inside the boot area just after welding. You can see the heavy concentration of welds around the turrets which the shocks bolt up into and in the first pic above the extensive welds around the front turret which the front shock and spring sit inside.
The thinking behind the placing of welds is as follows. When a car is used in a competition envirnoment it is driven hard and fast and quite often finds itsellf travelling over ruff surfaces and from time to time in certain circumstances it can leave the ground over jumps and return to terra firma with quite a bang. All these bumps, undulations and bangs are absorbed by the shocks and springs and in turn passed on to the bodywork/shell. With the vast majority of competition cars fitted with stiffer springs to give better handling the shock loading passed to the shell is often greater than that passed through a standard soft road car suspension. This shock loading is first transfered to the turrets that house the shocks and springs before being passed throughout the rest of the shell and as such its these turrets that take the heaviest pounding. It is therefore usuall to find the heaviest welding and beefing up of the shell in these points to counteract the heavy pounding. The next points for special attention are where turrets connect to the wheel arch and chassis legs and then where the chassis legs connect to the main bulk of the shell. Other points which come in for special attention are where the axles and subframes connect to the shell as these will also take quite a pull when the car is cornering hard and accelerating and braking hard. Finally all the major seams that that connect the major parts of the shell together take a weld to stop the body flexing under hard use. To gain access to the seams and suspension pick up points underneath the car has to be either lifted or turned on its side. On the majority of shells we've worked on, when they've been stripped out, they are usually light enough to turn on there side for this work and with the carefull placement of a few tyres there will be no damage to any bodywork.
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