i just replaced the headlights in my 66 with the sylvania ultra white 7" round ($12 each at checker) and now when i engage the brights the right light shuts off. all fuses are good could it be a bad bulb?
Either a bad bulb or the plug is making poor/no contact. Do you have a curcuit tester so you can make sure you have power at the bright terminal of the plug? You could also test it with your other new bulb to narrow down the possibilities.
The high beam and low beam setting of the bulbs have separate hot wires, but share the same ground. The hot wire on the passenger side is probably shorted somewhere. Try swapping the bulbs side to side. If then it happens on the driver's side, you will know it is a bad bulb and not wiring.