it seems obvious, heat really hot but then what? to i need to hit the head/bolt with a hammer for the bolt to fall off? or will it head and just fall off itself. Im going to use a propane torch from canadian tire and use to to burn the bolts off my cats to instal test pipes. Ideas?

 

Propane will not get hot enough to melt bolts. An oxygen/acetylene welder will do it. I'm assuming the bolts are rusted on? You could try heating them with the propane, maybe the expansion will break the rust. After the bolts cool, soak them over night with something like 'liquid wrench', then try to wrench them out. If that doesn't work, if you have room then a hacksaw or portable grinder may work.

 

there isnt enough room to grind them off thats for sure. and its difficult to reach in there to heat them with thte intention of using a wrench (the header to cat bolts are quite tight and require a ratchet with wierd extentions). Is there any advice using the welder, i know how to use it but have noever used it in a automotive sense

 

I just went out and looked at my engine. Man, you can't even see the exhaust from the top! Do you have your car on a hoist? If you can get at the bolt heads or nuts from underneath, just keep burning with the torch or cutter till the metal melts and falls off. Be extra careful where you are pointing the flame as anything not metal will burn. (wires, plastic etc.) If there are heat sensitive parts I protect them with a piece of asbestos. You can use a piece of wood, but keep a bucket of water handy to drop the wood into in case/when it catches fire.

Probably would be safest to take it to a muffler shop and have them do it for you.

 

yes i have access to a hoist, and have hoised it once when i attempted to instal the test pipes (with standard ratchets and wrenchs) With no avail. I am confident with a oxy/act welder and believe i can do it, im mainly worried about, as you said, melting anything that is not metal (wires ect). ill put some scrap sheet metal around the head/cat connection when i torch them. I was going to take it to the infiti dealer to have them do it, but they plan on chargin me upwards of 300 dollars... which is the cost of the test pipes in the first place

 

Don't forget that the scrap metal you are using for a shield will conduct heat. Make sure nothing flammable is touching it. Good luck!

 

try getting the nuts from underneath with one of these:

http://www.northerntool.com/images/p.../150244_lg.jpg

 

I've heard of those, would there be enough room for that down there?