Monday, February 27, 2012
Upgrading headlamps on a vintage Rolls Royce or Bentley
Have you ever wished for better headlamps on your Corniche, Shadow, or Cloud III? I sure have. Those old round headlamps were marginal when the cars were new, and now that both of us have gotten older, they really don’t make it for serious night driving.
The US government finally agreed with that point of view. Today’s cars have headlights that are at least four times as bright as cars of the seventies, with some ever better than that. And that comparison is new to new. Comparing a brand new car’s headlamps to the deteriorated bulbs and wiring of a 1967 automobile makes a much more stark comparison. Some of the vehicles that come to our shop have such poor lighting I’m amazed the cars weren’t wrecked before getting to our shop!
At Robison Service, our objective is to get as close as possible to modern lighting performance, while remaining true to the car’s vintage look. In my opinion, that rules out all HID conversions; there was no such thing as gas-discharge car lighting in the seventies.
The simplest conversion is installation of halogen sealed beams in place of the original units. That’s an improvement, but not enough for me. Next up the ladder is the fitment of H4 aftermarket headlamps; the most common ones come from Hella and Cibie. Those are better, but sill not the best we can do.
What we have settled on are a pair of H1 halogen bulbs with Hella bi-focal low beam lenses complimented by a pair of H1 bulbs in Hella parabolic high beams. These lamps have an external appearance that’s almost indistinguishable from stock, and the brightest and most efficient optics of any lamp in this size class.
These lenses are the easiest part of the conversion. They are direct replacements for the sealed beams. You remove the single screw the holds the headlight cover and lift it away. Three Phillips screws hold each headlamp retaining ring; the screws are loosened and the rings twisted slightly counterclockwise and then pulled clear. At that point the headlamps drop out, held only by their wires. Changing that over is what takes all the time.
If you do as we do – fitting H1 lamps – you don’t have any choice about changing wiring because all the headlamp connections are different. However, plug compatibility is not the only reason for the change. The other is voltage, or rather, an adequate supply of it.
Headlamps are rated to deliver a certain amount of light at exactly 12 volts. If the voltage at the headlamps drops to 11 volts, light output drops to 75% of rating. If, on the other hand, voltage at the headlamps is 13 volts, the headlamps will deliver 30% more than rated output. As you see, a small change in voltage makes a big difference in light.
The only tradeoff is bulb life, but that’s not generally a limiting factor on vintage motorcars. Even at 13 volts, a typical H! bulb will last 200 hours or so, which equates to many years of driving the way most of these cars are used.
For people who drive in parades we fit what Europeans call city lamps. These are smaller bulbs that light the reflectors of the headlamps without throwing much light on the road. They make the vehicle visible but using them will not wear out the main beam bulbs.
Modern alternators deliver a solid 14 volts, even under load. There’s always some loss through the wiring, but we do whatever is necessary to ensure strong voltage at the lights, for maximum brilliance. We aim for 12.5-13 volts; enough for brightness but not so much as to reduce bulb life unacceptably.
Most of the time, we fit relays beside the radiator, with a heavy cable from them to the alternator. That takes the load off the switches and wiring, and ensures strong voltage supply. In addition, we replace the sockets and connectors out at the lamps with high power components that have less resistance.
Taken together, these changes will multiply the light output of your old car many times over. Night driving will be transformed.
The photo above shows a new light next to the original outboard high beam
And if that’s not enough . . . we can still get brand new replacements for the old style rectangular driving lamps from the 1970s . A pair of those under the front bumper will extend your reach even farther.