Before heating the springs with a torch, get a bunch of guys together and a couple of cases of beer. Turn up the boom box, drink and laugh at the Darwin Awards on the web. Make one future ex-friend the designated dialer... tell'em to punch in 9-1 and the phone and wait. Get under the car with your torch. Fire it up under the car.
Before ruining the first spring, inadvertenly pass the torch near the gas tank and that tiny leak you didn't notice. About now, the designated dialer should enter the second 1 to his phone and run like hell. The last thing to go through your mind will either be the gas tank and contents or thoughts of making this years Darwin Awards list.
This is intended only to tell you not to heat your springs - all around a bad idea.