I have a JCM900 4502 combo pushing two 12" 8 Ohm speakers. I run this into a VS 4x12 cabinet @ 8ohm for larger venues. Sounds great.
I also have a Carvin Legacy cabinet @ 16 Ohms sitting around that I used with my MTS3200 head.
On the back of the Marshall combo, there is a Ohm selector for 8 or 4(16).
Is anyone familiar with this. Can I push the Carvin, loaded with V 30's by switching over to 4(16) setting and unpluging the speakers in the combo?
I'd rather do it that way anyways.

Or, I guess if that was possible, switch out the 2 greenbacks in the combo for two V30's.

Thanks in advance.
According to this manual http://www.drtube.com/schematics/marshall/jcm900.pdf the JCM900 combos only allow you to select 4 and 8 ohms, and the speaker jacks are wired in parallel.

Possible combinations:
1 4ohm load = 4 ohms
1 8ohm load = 8 ohms
2 16 ohm loads = 8 ohms
2 8 ohm loads = 4 ohms
you might also be able to get away with a 8ohm and a 16ohm load which = 5.3ohms (use the 4 ohms settings, whatever you do DONT set the amp for more ohms than you have connected to it)

you could rewire the amp speakers in series for 16 ohms and the connect use them at the same time as the 16ohm Carvin cab in 8 ohm mode on the amp (but that means you could use the combo by itself anymore...)