Have 240v 30amp breaker need to connect a 240volt 40 amp cooktop can you do this I have a 103 600volt wire the cooktop power supply requires 240volt 4 wire 60 hz?

Yes you can. As long as you don't use 40 amps. The 30 amp breaker may kick off if you use all things at once. So you are well protected but not up to code. The 4th wire required for the new stove is probably a ground fault wire. So run a new cable or cook slower.