old pipes

for all you plumbers out there, or just those who play one on the weekend, i have a question. I'm replacing the boiler in my house - hot water, not steam. The old one's out, the new pad is set, the boiler is in position with the flu, gas, and electricals connected. At this point, i'm connecting it to the distribution pipes - supply and return. The old 2" and 1-1/2" fittings are an absolute bear to break loose. It's threaded black steel pipe. I've had some success with heating up the 1-1/2" fittings with a propane torch to get them loose. Several haven't budged yet, and the 2" fittings seem particularly stubborn.
I'm working with a pipe vise, and 18" pipe wrench with a pipe i slid over the handle for more leverage, and a 14" pipe vise to back things up when i'm working on the pipe in place - not on the bench.
Any hints, tricks, or sage advice (other than "call a plumber")?
Would acetelene or mapp gas work better?
Thanks in advance,
Paul Hubbman

Apply heat evenly around the fitting of the joint you are trying to break loose. Be sure two wrenches are used and are pulling against one another. There is a certain technique to use optimum leverage. Brute strength does not always work. Also hitting the fitting with a hammer helps sometimes. Also you may need 2 people one for each wrench and bigger cheater bars.

Sorry do not have a magic answer.

GOOD LUCK


Mark