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Modify your Mercedes-Benz

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Would you believe that we generally don't recommend that you modify any part of your Mercedes-Benz from its original specifications. That's right, so why have we done a modifications page? Good question? Mercedes-Benz design the best cars in the world. When they leave the factory they are the end product of extensive research and development. Ok, I will admit there have been a few mistakes along the way but over all they are great cars.

This extensive research and development that goes into these cars is aimed at giving the owner a compromise. Lets face it everything in life is a compromise. For example the difference between a comfortable ride and amount of body roll in a corner. So a well researched car will offer the new owner a compromise between all the variables that a designer must consider when designing a new model of Mercedes. Consider some of these points:

Comfort V's Handling
Power V's Economy
Top speed V's Acceleration

See what I mean each model has been designed to meet the requirements of the intended average purchaser. Obviously a 200D is different to a 450SEL 6.9 but the principles that the car is designed under is the same.

So I guess what I am saying is that if you are Mr (or Mrs) Average don't play around with what is already a great car. But if you want something abit different then have a go. But remember that Mercedes-Benz only employ the best designers and you have to be very smart to improve on what they have already done.

Here are some modifications we have made to one of our own cars.....

We have rebuilt a 1972 280E (W114) sedan to compete in Historic Rallies. Obviously this was not what Mercedes-Benz had in mind for this car when it left the factory in 1972. It was stripped to a bare shell and has had every single component rebuilt or replaced with a new unit. An expensive project but one with amazing results. It has given us an insight as to what a 280E was like when released back in 1971.

Compare this to what else was on offer from other manufacturers of the time in your country.

Twin cam 2.8lt engine. 185hp
Computerized fuel injection.
CDI (electronic) ignition.
Four wheel disc brakes.
Fully independent suspension.
All this makes the ideal basis to build a competitive sedan for Historic racing. When deciding which model to use we also took into account the choice of Mercedes-Benz Germany when they entered and won the 1977 London to Sydney Marathon. Of all the models they could have chosen they chose the 280E. I can only presume that they considered the 280E to be the ideal mix of power, fuel consumption handling and reliability.

Here is a list of some of the modifications made and some notes to help you if you have a similar project in mind.


Still under development at this stage. Have made many modifications but are not happy with the outcome. What we are trying to achieve is more power but without making the car hard to drive to the shops to pick up the shopping. It is easy to just put in some wild cams and raise the compression so it will only run on methanol but to get it the way I want it is taking time. Remember what I said about being very smart to improve on the original design. Modifications to date include raising the compresion by taking 0.5mm of the top of the block and head, I have also used the a perfectly matched set of pistons that were supplied to us by Kolbenschmidt. The heads have standard valves but have been cleaned up and have heavier valve springs to handle the higher revs.

So far we have had tow differant cam grinds done. The first set produced all its power up high, which was great except in slow corners. However it also seamed to want to over rev, it was quite happy to rev at 8000rpm, which is well over the limit for a standard M110 engine. This proved fatal when it jumped out of gear with the go pedal on the floor, the tacho hit the red line so fast I could not react in time. It spun so hard that the valves caught up with the pistons just enought to ever so slighly bend each one. The engine was still running but with very reduced power. This was an interesting occurance as I am totally convinced that in any other engine it would have simply exploded rather than hang togerther like it did.

The second cam gring produced power much lower but created valve bounce at anything over 6000rpm, which was kind of handy as there was no need to look at the tacho, you could hear the engine about to red line.


The fuel injection system is basically the original Bosh D-jet system. We have fitted either all new or reconditioned components to ensure the system is reliable. We considered using the much simpler/reliable Bosch K-jet system but decided to use the D-jet as it offers much more scope to adjust fuel mixtures and it also kept the vehicle more original. Bosch D-jet is an electronic computerised injection system which is amazing when you consider that this is a 1972 model car we are discussing. The basic design of the system is that a sensor monitors the inlet manifold vacuum and after adjusting it to take into account external atmospheric changes send the signal to the computer. The computer also considers the air temp, coolant, temp and throttle position. After all this is done it tells the injectors how long to open for. The injectors are fired as the inlet valve opens by means of a set of trigger points inside the distributor. The amount of fuel injected is controlled by the opening duration and the fuel pressure. The fuel pressure is controlled by an adjustable mechanical regulator and opening duration is controlled as above. So this make getting more fuel easy. We have the fuel pressure regulated to 2.6 bar instead of the correct factory setting of 2.2bar, fitted injectors from a 450SE engine (7% bigger flow) and have played with the sensors.

The air cleaner has been modified to Ram tube foam style air cleaner from a 5.0lt Falcon XR8. This is rather noisy but makes it breather much better than the standard unit. One day I will make a cold air box for it.


Originally the car had an 4spd automatic transmission. (this in it's self was a great transmission and well ahead of its time) But, we needed a manual transmission to make the car more driveable. We purchased a 1978 280S (W116) that was made in South Africa for the wrecking yard. It had a 4spd manual transmission with the correct bell housing for the M110 engine. We replaced all the bearings and synco sleeves before installing it in the car. What I really wanted was a 5spd manual and I had heard that only two of these were imported into Australia in the 70's. Six months after we got the 280E on the road we purchased an old rusty 1972 280E for the wrecking yard with, guess what, a 5spd transmission. I am currently trying to track down some parts to recondition it so I can fit it.

(Stop press) I decided not to fit the 5 speed as it was just extra weight. If I had fitted it I would have been changing into 5 at just on 200kmh which is a speed I have never been able to reach on any of the hill climbs and short sprint courses I have competed on.


The tailshaft used is from a 250 (W114) manual sedan. The Auto tailshaft is shorter than the manual. We have used the tailshaft couplings from the 280SE W126 as these are the same diameter as the W114 but much stronger. The Rear 1/ 2 shafts are std W114 .


The differential used is a real hybrid. The crown wheel and pinion are the only bits used from the original diff. We needed a limited slip diff to improve our traction on slow tight corners and in motorkanas. For the first year we only used a std differential and suffered some major wheel spin problems. It took many hours of research to work out how to do it. We used a late W123 diff housing with a W124/201 limited slip centre and the original W114 crownwheel and pinion. It doesn't just bolt together either. There is a lot of custom engineering in it as well. We also had to cut the thrust washers on the end of the 1/2 shaft in half. This is not easy as they are only 2.5mm to start of with. These could have been left out but are important as they stop the 1/2 shafts from wearing away at the edge of the diff center.


The front suspension control arms are standard. All were fitted with new rubber bushes. A set of custom springs was made for us by a local spring manufacturer. The ride hight is approx 70mm below the standard ride hight. The front sway bar is a standard unit with upgraded bushes to keep it in place. It is interesting to note that the camber adjusting bolts on the lower control arms have enough movement in them to allow a "racing" wheel alignment without slotting the holes they go in.


The rear suspension as work of art. We used the aluminium control arm of the 450SE/SL . These bolt straight onto the W114 subframe. However this is the only easy bit. Many hours were spent on the rear sway bar as it also locates the position of the rear wheels.


The brakes are one of the most impressive assets of this car. When we came up with the concept off this car we wanted to make it stop as well as GO. The use of the 450 rear suspension arms gave us the advantage of anti dive brakes. As you may be aware most cars will dive at the front under heavy braking. This has the effect of taking the weight off the rear wheels and increasing the chance of loss of traction. The system we have used has the rear wheel caliper mounted forward of the disc rather than behind the disc. It is mounted on a carrier that can rotate slightly around the rear hub and push against an arm that compress's the rear spring to counter the effect of the front springs being compressed. All this means more weight on the rear wheels and less chance of a skid. The rear discs and caliper are the standard W114 units.

When we first started out we used the front discs off the W116 model. These are the same width as the W114 280E (but not any other W114 or W115 model) and have the same bolt pattern. They bolt straight on. The advantage is that these discs are ventilated. We also used the W116 calipers. These are the same as the W114 unit just widened to take the ventilated disc. These weren't quite as easy to fit as the discs as we had to make some special banjo bolts to adapt the brake hoses. On the W114 the brake hose goes into the caliper from the side and on the W116 it goes in from the top. After several competition outings we found that we were warping the discs when they got hot. The solution bigger thicker discs. We are now using the front discs off the Late model W126 sedan. these are 300mm thick and 28mm wide, which makes for trouble free brakeing no matter what.


HRA regulations only allowed you to go one inch up and one inch across in wheel size so our car was limited to 15" X 7" rims with 225/60R15 tyres. These fitted under the front gaurds just by rolling the ineer lip a little. The rear was another matter, we had to widen the entire wheel arch to ensire it did not touch on hard corners. The only other modification that was made was to reinforce the steering box mounts as we were aware that they had a habit of breaking on this model.

Since then we have fitted 17" X 8" AMG hammer style alloys which currently have a set of near new 235/45VR17 Continental sport contacts on them.

When I got the car it had had an aftermarket air conditioning system fitted, this was removed as like the gearbox it was just excess weight.

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