On Fri, 10 May 2013 16:51:02 -0400, Ralph Mowery wrote:

There was a vid on utube about drilling a hole where the old vent plug used
to be and using a tire valve that has the plunger removed. You use the cap
on the tire valve to seal off the gas and remove it when you want to vent
the can to pour the gas out.

Interestingly, you can buy that vent (for water jugs only, wink wink) online,
at the site that Steve W. recommended:
http://ezpourspout.bluesarthouse.ws/...roducts/parts/

They even recommend a 1/2 inch blade-type (wood) drill bit over a spiral
flute drill bit (they say the hole won't be round with a spiral bit).

Once you've added back the missing vent, then you can follow the YouTube
video which shows how to modify the spout to allow the gas to flow again.