I have a 79 pontiac formula with a 455 engine with hooker headers and flowmaster exaust. When i drive the car around easy there is no smoke comming from the pipes. However, when i get down on it, there is white smoke comming out the pipes. Also, when the smoke comes out you can smell something burning. What could be causing the smoke? By the way, there is somewhat of a small external oil leak.  

White smoke, especially with a burnt sugar smell is a sign of a blown head gasket. To check, you can make a simple bubble tester by drilling the center of an old rad cap and inserting a piece of brake line (make it a snug fit), put a piece of vacuum hose on the brake line, install the cap and run the hose into a clear container of water. Run the engine to operating temp and watch for bubbles out of the hose. There will be an initial stream of bubbles as the air in the cap gets purged but if it doesn't clear up in a minute or so, you have a blown head gasket, or less likely (but possible),a cracked head. Either way it's teardown time.  

THANKS, I WAS AFRAID OF THAT.  

Two things , if it has been doing it a while have you lost coolant or overheated.Is it from the pipes? to check have someone follow you . Also if you have an automatic you may be pulling fluid from the modulator valve through the vacuum line . An easy way to check that is pull the hose at the modulator. It uses vacuum to shift the tranny which increases with RPM. ( looks like a small can attached to side of tranny.
 If fluid is present in the hose then replace the modulator. It usually has a clip held by 1 bolt and slips out. Use a pan ,you may loose fluid.

               Good luck Eddie