Originally Posted by
SBinNYC
Heat accumulation is a problem with high power LED headlights. At best, it will result in inefficient operation. At worst, it will result in premature failure.
Modern LED headlights have integral heat sinks which vent heat generated by the LED to atmosphere. The case is an integral part of the heat sink system. The airflow at the case is vital for the heat sink to work. I'm afraid that putting a modern LED front light into an old case will not be a viable solution.
If you're using a truly vintage housing, you might just need to get good thermal bonding between the LED heat sink and the vast expanse of chromed brass shell. I used to have an LED head inside an old Union lamp, U100 perhaps, and the metal case had more surface area than most compact LED heat sinks. I used heat sink paste from my computer to get good thermal contact and it worked beautifully until the light fell off on the freeway when I had the bike on a bus...