Well, not unless you have some way to sync the two. The tape speeds of the two machines aren't going to be the same. You'll end up with 4 groups of 4 tracks that don't quite line up. A better way to get more tracks is just by bouncing. Record stuff on tracks 1-3 and bounce all 3 to track 4. Then you can record two new tracks on tracks 1 and 2, bounce those to track 3. With this technique, you can get 7 tracks with no more than 1 generation lost. If you mix in a live track every time you bounce, you can get up to 11 tracks. I you don't mind losing mixing flexibility and substantial generation loss, you can mix the bounced tracks to one track over and over, so you essentially get an infinite number of tracks out of your 4track. You need to be pretty meticulous in planning such a recording - think about panning, etc. ahead of time.