300SL Gullwing

A full concours restoration, every instrument apart to its last component and back together to a standard a concours field actually looks for.

What Arrived

A full set: speedometer, tachometer, clock, and the center combination gauge, which carries four instruments of its own: oil pressure, fuel, oil temperature and water temperature.

The owner asked for a full concours restoration, so every gauge came apart completely.

The Faces

Every face was blasted, painted and re-screened, including the front plate of the combination gauge.

One detail that matters more than it sounds: when a dial is re-screened, the original part numbers have to go back on with it. A concours judge knows where to look, and a dial without its numbers is a dial that has been replaced rather than restored. Ours went back on.

The Speedometer

Mechanism cleaned. The odometer and trip odometer wheels were restored, cleaned, the old crusted yellow numerals scraped out, and the numerals filled back in white. The pot metal frame was serviced, the magnet shaft polished, the magnet recharged. The brass upright gear and the pot metal gear frame were both replaced. Then lubricated and calibrated to the stock ratio.

The Tachometer

Pot metal frame serviced, magnet shaft polished, magnet recharged, lubricated and calibrated to its stock ratio.

The Combination Gauge

Oil Pressure

The mechanical movement was recalibrated, and we went further than a straight recalibration: we tested whether drawing on the coil itself would give a more accurate sweep across the whole range. That means unsoldering a component, unwinding the coil, drawing it out and putting it on the decades box to find the point at which it reads correctly. It is slow, and it is the difference between a gauge that is approximately right and one that is right everywhere on the dial.

Fuel

The same treatment on its coil, serviced, then calibrated.

Water and Oil Temperature

Both run on capillary lines, so both were checked for leaks. The lines were replaced and refilled with ether, then calibrated back to position.

New black plastic shielding was fitted, and the gauge sender nuts replaced.

The Clock

Cleaned, the movement rebuilt, and the timing adjusted. On the 300SL the original movement can be made to keep proper time rather than being replaced, and we have a technician who does that work.

The Finishing

Housings zinced. Lens retaining rings painted black. All glass lenses replaced. Every pointer stripped and repainted, with new aluminum pointer caps supplied for the speedometer and tachometer. The center plates on both painted black, and the dial screws painted.

The trip odometer knob was re-chromed, a chrome clock knob and set screw supplied, and new chrome bezels crimped on.

What Went Back

A matched set, correct to the part number, calibrated across the full sweep rather than at a single point, and finished to the standard a concours field actually looks for.