I have a 1975 Bryant furnace. The blower comes on right away, but no heat.

Not to sound mean but that's like me saying I have a 1975 Ford that will not start what's wrong with it? I assume with the older furnace you have a standing pilot. Is it lit and the gas valve set to on. As much info that you can give will help.

Yes the pilot is lit. When I turned up temp. on the therm. The blower kicked on right away, with no preheat and the blower keeps running but burners don't ignite.