A sealed beam is a headlamp assembly consisting of an enclosure with a bulb in front of a lens, completely made of glass. The entire unit is sealed and none of the parts can be replaced separately. Originally introduced for road vehicle headlamp service, sealed beams have since been applied elsewhere.
Sealed beam headlamps were introduced in the United States in August of 1939 after a three-year long development program, and became mandatory from the following year until the 1984 model year. Cars prior and subsequent to that date could have a variety of shapes of headlamps, using any of a wide variety of replaceable bulbs.
Sealed beams utilize parabolic aluminized reflector, and are thus known as "PAR" lamps. Round PAR lamp diameter is expressed in eighths of an inch, so a PAR56 lamp, for example, is 56/8" (i.e., 7 inches) in diameter.
Popular automotive sealed beam sizes are as follows:
- PAR30, PAR36, PAR38, PAR46, PAR56, PAR64
Let me give you some examples.
Almost all the USA vehicles through the mid-1970s used round sealed-beam headlights, either two 7” lamps, or four 5 ¾“ lamps. The 7” lamp is dual beam (one light operates as low and high beam), whereas 5 ¾“ is single beam (running only low or high beam).
5 ¾“ lamp
7” lamp
What might you do to liven the lights up? In fact there’s more than one way to go, but almost all the ways imply replacing sealed beam lamps and housings to get a detachable design and improved light output.
Some may try to convert into halogen sealed beam lights, which may save some money in the long run, since only the bulb inside is replaced rather than the whole unit. It will give you brighter light than OEM sealed lamps, and yet it is less bright than LEDs or HIDs.
Some may choose all-chrome or blacked-out housings, the light assemblies in the same size and shape as your factory ones. Usually they are available with halos or LED strips and represent a styling statement and still giving functioning low and high beam lights, but luminosity remains rather poor.
The most common bulbs you’re likely to find inside of a sealed beam are as follows:
- H6054
- H4656
- H4651
- H6024
- H4666
The fact is, since 1978 all the sealed beam bulbs would come as Halogens (at least, on the USA market), however they have different design from the contemporary Halogen equivalents and that, in turn, required different housing construction. Therefore, even though you get lucky to install any modern size bulb into your car sealed beam housing, you’ll be bound to enjoy poor visibility, let alone to blind the oncoming drivers and pedestrians.
We suggest you’d go with ordinary conversion LED or HID kits which provide much greater output while retaining competitive pricing.
As you’ve made up your mind to switch to HID or LED technology while your vehicle uses old sealed beams, you’d need to replace the entire sealed beam light. Besides replacing or modification of the housing is required as well.
