Just remodeled the kitchen and needed to move the range. The old 220 line is a 3 wire(Blk, Red and Green). Can I splice 13 feet onto it? Thoughts? It would be a pain to run 50 feet of new line sice the basement is finished

No, the NEC currently require a four wire connection.

Because you are changing the connection, you must use the current level of code.

Remodeling the kitchen requires the wiring to be brought up to current code, as Don mentions.

Discuss this with your local electrical inspector to see if he will require the range cable to be 4 wire, or if the existing 3 wire is allowed to remain.

Actually guys, the way he describes this...
The old 220 line is a 3 wire(Blk, Red and Green). ... is a straight 240v circuit. This CAN be extended. BUT... it CANNOT be used for a 120/240v circuit such as a free standing range or most wall ovens.

If this is going to be used for a range then it must be re-run. If it were used for a range before it was never correct.

Can you tell us what the circuit is going to be used for?