On a plate system, how long can the solenoids be left on?
Will it get too hot? or burn up?

Quite awhile, but heat will build the longer they stay on. I would say you would hurt your motor before the solenoids overheated or more likely blew a fuse.
How long are you planning to leave them on?
The way I look at it if they need to stay on longer than 11 seconds your car is not ready for nitrous......;):D

Its not going on a nitrous system, its for another idea of mine. It would need to be on for 30 min. or more...Thanks for the help. So that would mean, I need to comeup with a new plan....Thanks agin,,,Travis

You need continuious duty solinoids,a good Auto parts store should be able to help you find them.They look simular to the old ford starter solinoins that where mounted on the fender well. I think if you call a place that sells snow plow parts they may also be able to help you.

It would need to still flow gas. Thats why I thought of the nitrous.

give ma a call Friday @352-373-3578 ask for David @ ex.20 ,I might be able to point you in the right direction

i was thinking same thing but for hho instead of nitrous.