HISTORY IN THE MAKING - LLX358D TIMO MAKINEN’S HISTORIC RALLY – COOPER ‘S’

Having built one Cooper ‘S’ for Timo Makinen to use in Historic Rallying, in which he won two International Rallies,  I decided to build another one with more power and less weight than the previous one.

One lesson I learnt the hard way building the first car, was that a reliable source of new parts with in-built quality, especially where obsolete parts were being remanufactured, was essential.  Mini Spares of London satisfied these requirements hands down over any other supplier, and were able to help with technical/historic data as required.

Now, because so many good articles have been written about restoring Minis I will keep the basics to a minimum and concentrate on the special tweaks and tricks that we have learnt over the years, and having rallied an ex works Mini Cooper ‘S’ OBL 45F, complete with 8 port Arden Cylinder head and 4 Amals, there are plenty of those.

BODY SHELL

Complete strip back to bare metal and then shot blasted with plastic grit; this process does not require ripple panels.  Renew all rotten panels as required.  On this car this included new front wings, front panel, one inner wing, windscreen scuttle ends, inner and outer door hinge, ‘A’ panels, door skins, inner and outer sills, front door panels, rear boot floor, battery box, left and right hand sides of boot floor and boot lid skin.

To obtain a nice welded joint on the floor panels I butt welded the panels with oxy-acetylene and planished the joint while still hot and after finishing this gave a hard to detect repair.The engine stabiliser bracket was MIG welded along the top edge and reinforced with a gusset underneath on the right hand side.

The hand brake bracket was double skinned; the box section, which the front seals bolt to, was cut open and additional box section was welded in over the tunnel.  The original box section was then replaced and when finished, filled and painted,  was unnoticeable.  This is really the only weak point on a Mini and was found when the works cars were subjected to bumpy terrain.  Due to FIA Regulations it was necessary to disguise any reinforcements.  The rear bulkhead was fireproofed with fibre glass and the centre access hole plate was bolted in place with sealer.  The fuel line, brake pipe and battery cable were to be run inside the car so all grommet holes were drilled in the bar metal condition, all the electrical relay mounting holes and the additional dash panel mounting holes.

Front and rear subframes, known to be geometrically correct, were used to ensure that the shell was square, i.e. bolted in place as new panels were added.  All the tooling holes on the floor were welded up.
The shell was then prepared and painted with 2 pak  paint, the underneath and wheel arches being stonechipped first.

ELECTRICS

I was lucky to have John Smith of Lucas Racing to sort out this side of the project and because he wired most of the Abingdon works Minis, I knew there weren’t going to be any quality problems.  To reduce weight, I invested in Raychem wire, which is half the weight and what is used on Formula One cars.  Lucas 6RA period relays were used for main beam, dip beam, horn, fog and spot lamps.  Two Lucas 6FJ fuse boxes were fitted in the carburettor on the navigator’s side, and one Lucas 7FJ fuse on the engine side of the front bulkhead, above the heater fresh air duct.  One in line fuse dash panel, navigator’s dash panel, and door pocket panel (copies of original works ones) were wired individually and connected via snap connectors to the main loom, and all Lucas blade connectors were crimped and soldered.  Welding cable, because of its flexibility, was used for the battery cable.  Main earth connections to the body shell were ensured by additional MIG welding of the weld nuts on the shell.  All holes that the harness passed through were grommeted and the harness clipped into position with plastic sleeved P clips.  The four spot lampbar was made quick release by using a Lucas 5pin rubber covered trailer plug and socket, as used by the works.

SUSPENSION & BRAKES

Historic Rallying Regulations do not allow very many alterations to the standard Cooper ‘S’ specification.  However the wording regarding adjustable suspension meant that I could use Hilo suspension.
Front and rear subframes were shot blown, seam welded and powder coated.  The front suspension was built first using all new components.  The ball joints were lapped into their housings (this can be done using a normal power drill).  Putting the threaded portion of the ball joint, protected with some brass shim, use 600 grib grinding paste, hold the housing and check with engineer’s blue that you have removed all the high spots.  This tweak allows you to assemble the ball-joints once, without having to re-shim in 200 miles or so.  The steering arms were also lapped onto the hubs, having first surface-ground the steering arm faces – the works found that unless this was done, on a rough rally, the mounting bolts would work loose, so the better finish gives a better contact area and less fretting occurs.

The taper roller bearings were assembled using Castrol BNS grease (very high melting point).  The drive shafts were special in so much that they were made from EN24W material and the square circlip-groove was not machined.  A collar was positioned in the correct place and Tig welded in four places.  The square circlip groove on a standard shaft is the weakest point and if the shaft breaks it is always in this place.  New brake discs and callipers, with stainless pistons, were fitted and Aeroquip hose was used instead of the standard brake hoses.  Negative camber bottom arms were fitted with new mounting rubbers.  Hydrolastic top wishbones were used as they have the ball and socket housing machined further inboard than dry wishbones.   This increases the ride height and after sump guards and extra lights are fitted the ride height returns to normal.  Adjustable tie rods with front mounting protection plates were fitted.  These fit between the front panel and subframe and bolt, also to the side of the subframes, and adjustable Koni Shock absorbers finished the front suspension.

The rear subframe was built up using all new components with a few modifications (these were to help brake cooling),  The rear wheel cylinders were stripped out and  instead of using a circlip to locate the wheel cylinder they were threaded and nuts made to hold them in place, because the wheel cylinder is now solidly mounted to the backplate, heat is dissipated more effectively.  The backplate has cooling holes of 8mm diameter, drilled where possible on the brake shoe radius.  Eight 14mm holes were drilled, equally spaced, in the front face of the drum. A bolt and banjo were fitted onto the wheel cylinder and the brake pipe, covered in plastic tubing – screwed in the banjo thus avoiding the brake having to do a 90o  being exposed to stone damage.  Aeroquip was used and the rest of the metal brake pipes were plastic sleeves.

In the next issue of Mini Tech News, Tom Seal will be dealing with the trim, the Engine and Gearbox and the final set up on the Dyno. 

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