Mercedes-Benz Forum banner

Building your 107 to go hard

11K views 68 replies 13 participants last post by  prwizard 
#1 ·
The journey to building the fastest old Merc (W107) in the world.

I purchased the vehicle from a friend in Sydney in 2003 as a weekend cruiser. Whilst i had owned many European and Japanese go fast road cars this was the first Merc i had owned.


It attracted me as a very elegant car that had “old school” character and a great car to cart blondes and Malamutes around in. I also used the vehicle as a commuter for soft days to the office and back and hardly ever put the roof up. The Australia weather offered magnificent motoring opportunities and it was an instant hit with friends and colleagues. During this time i decided to upgrade the 3.8 litre engine to a 5.6 litre that came from the backstreets of Germany. This was the factory derived high compression 225kw motor.

In 2006 on the basis on its superior engineering and style i also purchased an R230 to replace it in its commuting role as i had moved to Melbourne and needed all the creature comforts associated with suit wearing behaviour. Of course i had to get matching colour and wheels. The W107 became a weekender only as well as a dog taxi, the rear parcel shelf was the perfect size to sit a 50kg malamute in. Its usage decreased and was mostly garage bound in winters.

Having a shack in the bush in Tasmania meant an opportunity to trailer it to the frontier and to wiz around on the endless windy roads in the local area. There is also a large tarmac rally called Targa Tasmania that ran close to my place.

I assisted with roadside controls for a few years and then was invited to do a road control car which meant running with road cars that paid to run on closed roads but were not FIA safety equipment certified. This was typically the exotic supercar club that were not racers. After doing this for a few years and continually having to restrain the old girl and realising that maybe i am mot that old yet, i decided to enter the entry level rookie rally. This fundamentally meant mainly safety equipment, some suspension work and limited race equipment. Alas it turned out to be an engineering disaster with the engine breaking 3 times during the race, though we did solder through and finish the race. However as the navigator was driving the car back to the boat it finally let go. You can see the old girl struggling to get home here Mercedes SL Targa09 @ Longford - YouTube

The next year we spent much more time on the engineering side and ran the full event and also finished well. We were also highlighted in the award ceremony with our exuberant driving from the official photographer who took this picture. Some footage from one of the street sections can be seen here

There was a lot of positive feedback from the crowds who i believe have become bored with watching a whole lot of modern boring them with their “tyre strategies” and all that internal motorsport stuff that doesn’t translate well to anything entertaining. A lot of people enjoyed seeing an exotic classic being operated in such an irreverent mode. I think it is something about the “Top Gear” flippant approach that the fans seem to find exciting. Much of the modern road racers take themselves far too seriously and their personas are not very popular with crowds. It seems to me that the classic cars represent an era before computers and polished egos sapped all the joy from the street based races.

Alas not long after this yet another engine let go and this caused a dramatic rethink as the budget was well and truely blown. After much soul searching we decided to run 2 motors, an authentic one for large events and a Chevy LS3 as a track engine. The philosophy behind this was to preserve the 5.6 motor for events were factory conformance was critical and flog the track engine night and day. This was borne of extensive research on the engine metallurgy and discussion with Silver Arrows racing in Belguim. It appears that the first alloy engines had a serious flaw with the levels of silica in the metals. Coupled with this and the very tight engine bay fit the engine was getting wildly hot, pinging and eventually causing catastrophic failure.

The exercise in fitting the engine was an engineering epic. Taking several months of staring at an engine bay we finally got the new engine to fit. I had researched others who had gone through the same conversion process but found all of them had really just kept the shell and made major modifications to the entire car. There is a particularly fine example of how to pimp my ride built by a guy in a wheelchair in western Australia.

However our design principles were to make the operation completely reversible so that we could retrofit a new M117 engine. Much of the conversion issues revolved around engine placement as the bay is actually quite small and the steering arm is exactly in the way. Most people rip it out and after that they own a drag car not a racer. Our fit out can be unwired, unplumbed and unbolted and the original engine fits back in without any modifications, though we need different tailshafts and gearbox mounts.

In the end the clearances were very close with 4mm clearance where it was tight and 5mm where there was plenty of room . In fact it is so seamless that the non aficionados can’t actually tell it isn’t the factory engine. Of course the fitout design was highly problematic but, we believe unique for anywhere in the world, in the sense we want to go fast point to point. To this end horsepower is not that relevant as the chassis can really only cope with circa 450 horsepower which is 100 horsepower more than the factory ever got to.


To cope with the excess power the list of suspension and brake modifications got more serious. Though none of the original suspension geometry was modified, merely springs and shocks upgraded. This has happened 4 times during the life of the car and now front sporing rates are a ridiculous 1250 lbs, about the same as a light truck. However the handling is superb even though it is a still loose on the road as you can see from this video at the local track in Tasmania.

The shocks are all custom built gas Bilsteins as the car was originally lowered 3 inches but then raised nearly an inch to counter for the extreme travel needed in tarmac rallying. The rear brakes are standard but have to be basically rebuilt after each race whilst the front brakes are similar to specifications to the Australian V8 supercar specs. They have never faded but do shudder dramatically whilst they are warming up. The roll cage was like most of the modifications were custom made and much analysis took place to ensure the modifications were both effective and modified aspects of the car were minimised. Looking from the car externally it is hard to tell that it is not factory, apart from safety equipment and standard performance upgrades the engine is the main aspect of the car that would make the aficionados cringe.
The next project is to attempt to get a high performance original engine. To this end i have been in discussions with Silver Arrows Racing in Belguim home | Silver Arrows who run the authentic cars in Europe. Alas the options to buy from European engine builders are expensive and there is virtually no expertise in Australia to install and maintain them, let alone tune high performance options. As such without any sponsors this option is currently on hold and i will run club events that do not require strict factory specifications conformance. Should there be any readers of this article that are interested in getting involved i would obviously more than interested in talking to them.
To promote the brand and keep the “old school traditions” alive i have developed a poster that can be given out to spectators. This shows the car in various extreme postures from various races that it has been in as well as some of the engineering aspects.

Another type of racing i am contemplating is more serious track events. The Tasmanian Super Sprint series which has 3 classes of vehicles ranging from million dollar Lamborginis and Godzillas down to cars of a similar performance of Der Panzervagen. This is a more serious race event as opposed to track days or club events. This runs like LeMans where the cars with dramatic speed variation are all on the track at the same time but a scored on class times. It differs from a normal club event where i am in the right lane overtaking to being a little fish in a big pond. I imagine i would spend a lot of the day in the mirrors trying to keep a clean nose.

tubeface channel with all the action is at TargaMerc - YouTube
 

Attachments

See less See more
2 1
  • Like
Reactions: unavita
#3 ·
During my research about engine replacements i had quite a bit of dialogue with them, particularly Philip Lecomte, the team manager.

i tried to buy an engine from them but they don;t seem interested at all in selling SLC's.

One thing i do know if you managed to convince them you are looking at BIG BIG $. I would think a rolling chassis is $100k +, and engine built by their mates in Belgium is $50k entry level, the installation and tuning would be another $50k, then who the hell do i find to tune and maintain the dam thing as an M117 in that state of tune is brittle and precious. They also have a 3 mechanics that go with the car to every race. Unless you wanted to put in your private museum i think you are better off building your own.

Of course you may not need to drive in the maniacal style that i do and which case a club car with a well prepared standard config may well give you much more fun per $ than something that is fundamentally a World Championship grade vehicle.

I sent them some of my videos and they were rather impressed and actually invited me to come to Europe and drive Bjorn Waldergardes car. during the engine angst time i was seriously considering this and bring back one of their SLc's but in the end budget kills most of our aspirations.

May still go to Europe sometime in the future to at least have a drive
 
#5 ·
All racing engines are expensive. I knew a guy that went broke buying them. His driver did well. This same fellow was a high end Porsche Mechanic in another life time. He did/ had done work on mine that I swear felt like it doubled the speed.

Though not a MB guy per se, his thoughts on a 450 were that it would go a long way to improving it if over sized cam lobes and a better fuel injection system were utilized. Pistons are a problem in that all the 107's used low compression engines compared to American muscle or Porsche engines. The guy that rebuilt the heads, cam and valves on my Porsche is still around. Kelly's Automotive specializes in racing heads. It's in West St. Paul, Minnesota.
 
#8 ·
M117 hardening

More thoughts on this engine

the main drama is pre detonation, that was what blew up my 2 engiens so far.

this has a number of contributing characteristics
the metal qualaties of the 80's technical immaturity.
From what i can see is the silica ratio which is very different in modern engines
the tight engine bay with little room for evacuation of hot gas especially at the top near the windscreen
the lack of any electronic management systems
the very heavy construction of the pistons and rods

Merc are not alone in this, if you look at a lot of the US muscle cars of the same era they could get no more than 1 hp from each CC, which is why they are famous for solving performance with cubes unlike others than modify the state of tune.

I also thought about the megasquirt low level supercharged thing but lacked technical assistance in Aus

If i were spending $ on a standard club track day car i would probably
  1. Find as clean ablock as i could
  2. HPC the block
  3. upgrade the radiator to race spec
  4. run a seperate oil and tranny cooler
  5. look at a Motec or equivilant engine managment system
  6. get some custom headers

when we looked at it we figured we could get about 350 - 400 hp without making it too brittle. that would make a significant difference and give you some good mumbo for track days. in reality unless you are going to spend $30k on brakes and suspension (= 3 hyundais) there is little point in anymore hp than that. even with all the work i still struggle to get the power on the ground under race conditions

i found the native 560sl brakes ok for an M117, get some serious pads though

the big thing is too race to a budget

One thing is for sure they are always popular at the track and entertaining given they are loose on the road
 
#12 ·
There is certainly no question that if you want to throw $ at anything you can make it go hard

i am reminded of the Sauber C8 that ran a M117 at LeMans, the ultimate test of power and endurance
Sauber C8 - Wikipedia, the free encyclopedia

but a club day car doesn't need all the brittleness that goes along with extreme states of tune, its a real drag when your day our racing hits technical problems and you have to put it back on the trailer

apply the 80/20 rule and you can make a fun car
 
#28 ·
glad you enjoy it dude
there is also a data screen that comes with it that provides some excellent feedback

One of the club guys has got some external film for me so i might do a "Der Panzveragen so far" highlights thing

if you are interested i could send you a DVD with the HD so you can watch it on your home theatre

if i can figure our how to afford it i might bring it to the US for some tack days and we can get all the US merc guys out for some hell rides, or if you want to come out to Aus we can arrange a track day down under
 

Attachments

#26 ·
The problem with boring cylinders is it raises the operating temperatures. More than .040 over will surely shorten the life of any race engine. Stroking a V8 motor results in different catastrophic results because it changes the rod angle putting too much stress on the crank and the rods. Cubic inches equals horsepower, yet these changes will usually result in engine failures if they are not carefully analyzed. The answer? Turbo and Supercharging...
 
#27 ·
the engine to get is the M117 that was delivered in the german domestic SEC's they were the native 225kw hi compression

they have the basic specs without the need for wild, expensive and brittle mods from factory basics

you simply need to clean the motor up, port the heads a bit, a set of headers, look at electronic ignition controller and cram as many radiators under the bonnet as you can.

don't muck around with fundamental factory specs or you will end up with
 

Attachments

#40 ·
this forum certainly does put forth some excellent suggestions

AND now a treat for the supporters on this site
i have just got in some of the best out of car footage at the track yet

i am going to use it to make up a compilation from different angles mixed down

but in the meantime i will put up the raw material in a private link just for you guys. i'll upload when i get back to the mainland and the government can pay for the upload

here is a snippet of teh action
try this private link
http://www.youtube.com/watch?v=pvmp9jLoQgU&feature=youtu.be
 
#47 ·
there is about 10 mins or so i will upload but that was about the furtherest away form it i got.

i am going to do a compilation matching the inside to teh outside so we can all get a better picture of it

another snippet being uploaded now
external snippet 2 - YouTube
external snippet 3 - YouTube

enjoy
 
#48 · (Edited)
This is interesting stuff. I have enjoyed many of your videos earlier on youtube, and thanks for sharing the backdrop for these. I think its great that someone use the 107 like a proper racer and brings it out in the public. I always enjoyed it when classics smother modern racers :). Jap drifters and modern track cars overtaken by an old merc always brings a smile to my face. Have you seen this 107? Serious car. I have no details.
YouTube - SLC on the Nordschleife.
 
#50 · (Edited)
prwizard, hats off to you & your exploits mate.
This is the car in the video... not the stuff of us mere mortals, yes this is some serious shit here, I believe its one of the "SLC racing" cars...
 

Attachments

#68 ·
What did they want for the ordeal then? Looks like they provide the full team with equipment, car, mechanicsm the lot, so that one can pretend to be a race driver for a while.. Sure takes part of the fun away when it all is handed to you :). I wouldn't refuse though...

Did you check out the eastern european SLCracing.eu? They build SLC Mampe replicas. I have never seen or heard any actual cars built by them, but from the looks of it they have their garages full of donor cars ready to be converted to full thoroughbred racecar classic replicas. From what I have heard their prices have apparently sky-rocketed in the last years, but that is only rumors.

The problem is that, when the cars become so custom and uses so many rare or unique parts and are so pricey, racing them will inevitably exponentiate the costs.

Nevertheless, the replicas look fantastic though: SLC Racing : manufacturer of Mercedes SLC 500 Rally Cars
 
#69 ·
It was about $30-30K a race with all teh corporate fluff supplied - rock star for a day type stuff

i prefer to use that $ to build up my own asset and brand

The SLC Racing a slovak guys that do cheap welding, the reason you have never seen a comp car is i don't think there is one competing. The Silver Arrows guys buy their shells from them but thats all they do

they are world rally speced vehicles, you need a factory grade service team, thats where you burn the $

i don't have team at all, very basic pre flight checks then on the trailer
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top