Mercedes 300SEL 6.3 Racing Project

GeoffCapes

Member
Messages
14,000
I can see a bit of OCD coming on with the weight saving.

What an epic car that is though.

What colour are you having it sprayed?
 

Grant V

Member
Messages
242
If this was to be a show car, then it would probably have been at this point that I started to strip the car down for paint. However, this is going to be a racing car, so there are a lot of things to attend to to make it a competent racing car, as well as race legal.

The car was getting hot when I had it out on the track two months ago. It was recommended that I use two fans close to the radiator, but that would be a last resort as I still want the car to look original with the single fan. (There’s this constant tension between wanting to keep the car looking as original as possible, but also wanting it to be a decent racing car. Sometimes it’s a very conflicting situation.) One of the things that I did want to attend to was the under-bonnet heat, bearing in mind that the temperature gauge sender unit sits at the back of the cylinder head in a place where there is probably the least air flow. The historic racing regulations ban any louvres or vents in the bonnet unless it was there in period, so I came up with another plan. I cut out two holes on the firewall so that air could flow into the air box.

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I made a hole in the bottom of the air box with a mounting bracket for an air duct.

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I bought a small fan used on KTM motorcycles and attached it to a bracket and then mounted it inside the wheel well in the original hole for the interior fan.

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A duct was then connected to extract the air and works well. I then made covers over the original vent holes to prevent any air from entering the air box.

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Theoretically all the hot under-bonnet air should be sucked out from the engine compartment and expelled into the wheel well. I fitted a separate switch to the centre console to start and stop the fan.
I also shrouded the radiator to prevent any air from going around the radiator instead of through it.

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A battery cut-out switch is a regulatory requirement in case of emergency. The cut-out switch must also be able to be activated externally by a marshall if need be, so the simple solution is to have a cable attached to the switch lever, which can be pulled to move the switch into the off position. I had a cable made up and then mounted it in place.

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The front windscreen and rear window have been removed and sent away to a company that manufactures Lexan canopies for helicopters and aeroplanes. They have done a lot of work for guys in the racing world, but will have to make moulds for the windscreen and rear window of the 6.3 first to make the Lexan copies. Normally a rear window will be made of 3mm Lexan and screwed into place in the window frame, but I want to use proper window seals with their trims, so the windscreen and rear window will be made of 6mm material. It will still be lighter than the original glass.

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A big weight saving will be to replace the original fuel tank with a small aluminium tank, like on the AMG replica.

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The company that sold me the extractor fan can make me a fuel tank, but they need drawings so I set about making a mock-up of the tank from cardboard, using the various photos that I have as a reference to get the proportions right. I have now given them the mock-up and the drawings and hope to have the tank in about three weeks.

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The fuel filler and cap are exactly the same as on the AMG car, and actually come from a Land Rover, which would explain the 6.3’s oil leak. The filler was straight, but I needed to cut it and re-weld it at an angle to line it up with the tank.

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The last few weekends have been spent saving weight. I started with the bonnet by removing the hinges and springs, removing the strengthening bars and cutting away the edges of the bonnet. Without the hinge springs, I needed to make a bonnet stay to keep the bonnet open, using a piece of aluminium tube.

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I also drilled holes in the brace at the back of the bonnet and all in all the weight saving has been 2.2kg

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I cut out the inside of all four doors and drilled holes in the bottom of the doors – you should see any difference once I have door panels in place from a normal door. The total weight saving has been 6.8kg

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I removed all the brackets for the spare wheel mounting in the boot and then removed the boot lid hinges and springs. Each spring is almost half a kilogram. I cut away all unnecessary parts on the hinges and then drilled them to save weight.

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I removed the boot lock and striker – unbelievably this is almost half a kilogram as well!

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The inner strengthening frame of the boot lid has been cut out, which lightened the boot lid by 4 kg, from 15.9kg to 11.9kg. Two panels have been cut out of the rear boot panel as well.

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So far I have saved a total of almost 30kg.
 

Grant V

Member
Messages
242
Thanks, Phil. I've enjoyed every minute of this build and if anything I've learnt about enjoying the journey. I used to be all about the destination.
 

Grant V

Member
Messages
242
Any significant work on the project stalled for most of 2017 as we started home renovations, and anyone who has done this will know that a three month build went on for nine very long months. However, in December last year I began stripping the car down entirely to send it in for paint - everything was bagged and labelled, and I took as many photos as possible to ensure I would remember where everything goes back again.


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I then set about making the grills to cover the air vents on the bulkhead for the under bonnet heat extraction system.
A template was made out of cardboard which was transcribed onto a steel sheet that was then cut out. Two of these were made for each side and the fly screen material was clamped between the steel frames. The left hand side grill was a bit more complex that needed some bending to follow the shape of the bulkhead. The steel frames still have to be plated and I'm happy with the result.

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All the wood was sent for re-furbishing along with the chrome and I spent the next few weekends making a trolley to be able to move the car around and get it to paint.

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By the end of March the car was taken in for painting.

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Grant V

Member
Messages
242
Two weeks later I popped in to the paint shop to see how the race car was progressing and I was very happy with the progress so far.

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I was so excited to see how good the car looks so far that I was inspired to get home and strip down the engine. Not that I would allow the lack of a decent engine stand to stand in my way.

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Engine was in good condition - crank will only need to be polished. Bores are also okay, but it will be re-bored anyway to accommodate the 6.9 oversize pistons that I was able to find through Tom Hanson.

The next four or five weekends were spent tackling the wiring harness. I bought a sheet of chipboard and laid out the wiring loom. The car had to be re-wired because a lot of the wires in the engine compartment were hard and brittle, like those running from the alternator. I had also removed a lot of wiring, particularly anything to do with the electric window, interior fans, door/light switches and so on.
My friend Alan, who's the best sparky in the world, helped me re-make the loom. We used wire that was still in good condition, but also had to add in extra wire, e.g. for the fog lights. All the sleeving was replaced and I ordered new electrical plug connectors where they are missing, like on the alternator where modern spade connectors have been used. We wanted to use all the original plugs, but they had to be removed for the new sleeving, so I removed each plug, photographed it carefully so that we would know which wire goes where and then labelled it accordingly. The new grommet that seal the loom into the firewall needed to be fitted as well.

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By the end of May most of the chrome was been returned - some items were sent back because the quality was not up to scratch. I plated the relevant metal parts for door knobs and fitted them - every little step is a small victory. I've come to the conclusion that I'm a total pain in the **** (only I'm allowed to say this) when it comes to putting these parts back together. At the end of the day the door handle parts are behind a door panel and nobody will notice if they're dirty or rusty..... but I will know.

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By the middle of June the wiring harness as completed ready for installation. Some wires were made longer and the plugs left off to be cut to size once everything was in place.

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Grant V

Member
Messages
242
I collected the car in the middle of September and was absolutely thrilled with the paint work.

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Work started in earnest to re-assemble the car. The headlight units were restored and fitted with new main beam units. The bezels were re-chromes and new park/ indicator lenses fitted. The old headlights at the top were retained, but covered in black vinyl, as per the original.

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Other things that make the biggest difference have been done, like fitting the tail lights and boot lid badges. The side lights which illuminate the number sticker at night were cheap Autozone tin plated number plate lights, which I had powder coated black and installed. The re-chromed window frames for the doors have also been fitted, along with the doors locks and strikers, which were re-plated as well.

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The wiring harness was fitted only to find that the grommet in the firewall was the wrong part – it was too big, so nothing could be connected until the correct grommet is found. It will have to be pushed in from the longest point, i.e. the right headlight.

In the meantime the pedal box was disassembled, powder coated, re-plated and refitted.

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Grant V

Member
Messages
242
The brake booster was re-painted, the aluminium spacer sand blasted and re-assembled into the car with a re-painted brake master cylinder. The air suspension distribution valve was overhauled, sand blasted, connectors re-plated and re-fitted with a new control cable. The wiper motor was painted, plated and installed.

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The steering column was re-painted and temporarily fitted so that the brake/ air pipes could be routed. All the brake and air pipes were sent for plating, but came back out of shape - they had been bent to get them into the plating tank. Bending them back into shape and re-fitting them was a real pain in the **** job, and was really time consuming. Securing brackets were re-plated and new mounting rubbers installed. Rear bellows have also been cleaned up and installed - these were refurbished some time ago already. I'm not crazy about the dark yellow zinc plating as it is now, but it will fade over time to a lighter, more normal colour.

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The front quarter vent windows were replaced with poly carbonate windows cut from a 5mm sheet, and inserted with the original securing seals into newly chromed frames. These were re-assembled with new window seals and re-fitted. They are indistinguishable from the glass windows until you tap them.

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The trim beadings have been a source of concern as most of them have scuffs and scratches. I sent in a sample piece to one of my suppliers, Astro Anodising a few months ago. It came back okay, but not as shiny as the original. My reckoning is that like with any other surface treatment the final product is only as good as the preparation, so I bought a polisher, got Astro to strip the old anodising off and then spent a few hours this past weekend polishing the rear windscreen beadings. I started with 220 grit water paper to get the scratches out, then 400, 800, 1000, 1500 and finally 2000 before polishing the beadings with a green colour soap, recommended for fine polishing of copper and aluminium. I'm very, very happy with the result and will now send the beadings back to Astro for mirror chrome anodising. Hope my theory works, otherwise i will simply have all the beadings stripped, polish them and clear coat them.

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A Friday afternoon was spent working out the sizes and proportions of the various decals needed. I got to see the graphic supplier on the Monday and hope to have them all within three weeks.

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The front suspension was overhauled a few years ago, so I just had to clean it up and them re-install it. All the air pipes have now been plated and connected.

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Grant V

Member
Messages
242
The rear suspension was also overhauled a few years ago, so it also just needed a clean before being re-fitted.

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The alcohol jar was bead blasted, plated and installed.

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The auxiliary fuel pump was fitted with the fuel filter, which was also bead blasted and plated.

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Fuel pump cleaned up and fitted

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conaero

Forum Owner
Messages
34,593
WOW, just WOW.

I just wish I had more time to do the same to the Opel GT...Keep it up, I know its a tough old slog.
 

Goodfella

Member
Messages
735
Christ alive this thread makes me feel like I really should do something more than just work & drink wine....

Lovely W124 convertible as well.
 

Felonious Crud

Administrator
Staff member
Messages
21,013
My God, Grant, that is lekker gorgeous, bru! Well done. You write a very calm description of the work you're doing, but I'm sure most of us would have lost patience a hundred times by now. Good job! And keep the updates coming.