Problem-engine ingesting coolant!?

[Bandit]

Hey guys,
My engine has recently started burning up coolant at an increasing rate. It started when I installed my new head gaskets, they are flat copper gaskets--I found out later that the block should have been o-ringed for proper sealing. Anyway that wasn't done, and some coolant seeps down from the heads in one area on the driver's side. But the worst problem is that it appears to be sucking a lot of water through one of the passenger side combustion chambers, you can see it spit out the tailpipe, especially on cold startup. I have had to add about a gallon every 50 miles or so and it seems to be getting worse.
There is no coolant getting into the oil--the oil is staying nice and clean. But there is obviously a bad seal between a water jacket and the combustion chambers because you can smell gas in the radiator.

Is it OK to keep driving it like this for now? I am running pretty much 100% water for now, since the weather is warm. I plan on installing new heads soon, and I will get the correct gaskets then. But will driving it while it's sucking up water hurt anything?

Also, if you have any good recommendations for head gaskets for a BBC 402 (About 9:6:1) I'm all ears!!

Paul