The headers arn't THAT bad to install..but your best bet is to just tear everything apart and start over.
I started the header install by taking out my downpipe, inlet pipe, and cat/test pipe, as well as my old headers and crossoverpipe.
To make it easier on yourself buy the Poston crossover..it is made for the headers and the whole system will just go together much better.
Start off by installing studs into the header to Crossover flanges. Secure the studs in the header side of the flanges so that you don't have to worry about stripping bolts. While you have the passenger header off install studs into the header flange where the inlet pipe bolts up as well.
I prefur using studs as a mounting method, because you no longer have to worry about holding nuts or dropping bolts.
Now that you have all the studs installed....bolt up your passenger header. Torque them all "Nice and Tight" with the copper gaskets from Poston. Then go over to the driver side and bolt up the driver side. After that you can bolt up your crossover.
Before you bolt up the crossover fill the inside of the "bell" mounting flange with Permatex Coppercote. With the studs you installed it should be EASY to line up the crossover. Line the studs up with the holes and put the nuts on. Now you must tighten all of the bolts...but EVENLY. again...Using the studs as a guide tighten the crossover so the same amount of threads are showing on the other side of the nut...Using this as a guide will assure you that both "mounting bells" are evenly tightened, and if not the permatex will fill in the small gaps.
Once that crossover is tight do not start the car to allow the permatex to cure for about 24 hours.
While your waiting you can bolt up your inlet pipe...again use the studs that you installed before hand..I use a specialty gasket in the flange of the inlet pipe as well as permatex at the header/inlet pipe connection. Once those are loaded in the inlet pipe I tighten down the inlet pipe..Using a gasket AND Permatex is the only way I have been able to get a tight seal at the connection.
I didn't forget about the down pipe...If you can install the downpipe after all of this..do it...if not then you may be forced to install the headers with the downpipe inplace...which is no treat.
Start the car and let it get up the operating temperature....then let it cool..and retorque the headers, after 2 days retorque the headers, and then one week later re-torque the headers....Why? Because Copper is very soft and the constant re-torquing will not allow the gaskets to compress further and provide a nice seal.
Just take your time, and remember..its just a car...doing Engine exhaust work on these cars is no fun...but the Performance that you will gain is noticible!
Hope this helps you a bit.
