My biggest issue has always been passenger side header leaks. First with the stock headers that I paid to have taken apart ported and rewelded. They just kept cracking. Got tired of taking them off and rewelding them so I bought the Poston setup (headers and crossover). They did look great and the size of them compared to stock, you could just see how much more they were capable of flowing, however.......
Dealing with my ATR uppipe was the worst part now (which I believe was ATRs fault in design not Poston). Had to deal with it by finding a donut flange gasket to stick where the header and uppipe meet. Should be made so that it was just a flat surface meeting flat surface there like the pipe is at the turbo. This passenger side header also cracked on me a few times. Rewelded and started feeling like I was going through the same thing I went through with the stockers + the additional fun with the uppipe which was a bear to deal with to seal again every time you took it off. [Maybe just to give Poston the benefit of the doubt] one of my theories was that because of the way the ATR uppipe was designed it was putting stress on the header which was causing it to crack. Finally sent the headers back for another set, just to have the same issues before long. At least I had found out the deal with sealing the uppipe by this time
Also discovered somewhere along the way that there was also a leak from the #2 exh port towards front of motor. It seemed that I had finally tackled the deal with the uppipe (with band-aid in form of stupid donut gasket), and the cracking issue (after some of my fancy mega mig welding). Yet another theory based on the previous theory is that this time since I tack welded the crack first while in place on the car with uppipe attached, is that the header was now moved where it needed so not to be stressed by the uppipe anymore. The deal with the leak towards the front however, I never could completely get rid of. Oh yeah, and I was using copper gaskets from day one. I actually tried some felpro's with copper rtv a couple times and got them to seal leak free for about a week, so then it was back to the copper ones.
Not too long ago just to try something different (again) I bought a used set of old Lee Thompson headers, crossover and a TH style 3" 3pc Dp from a board member. These dont look quite as big and nice as the Poston ones. However on this set the flanges are all flat against flat (except at the uppipe to turbo which was like stock; but I cut the pipe and welded the flange so that it is now just like the ATR one there). I bought a sheet of gasket material with the metal in between the composite and made my own gaskets for all connections except header to head. There I went with some felpro's (not sure why), blew them out in a week and stuck my used copper gaskets on. I wish I could say I am now leak free but I still have that leak at the #2 port. I bent the part of the gasket that sticks out a bit, towards the header with a pry bar and it helped to silence some of the ticking but still not completely gone. Other than that the only leak is a slight one from where the DP meets the turbo which you really only notice a bit at start up. Dont know if copper gaskets wear out and I need to get another set (expensive if I remember; been awhile)
or I should just try the one thing that I havent and install the header without a gasket at all.
Header leaks IMO are the single most annoying thing about these cars. It is the only thing that I have been beaten at every time on this car and cant seem to overcome completely. Man it felt good for that week of tick free driving with the felpro gaskets on there
I really would have liked to stick with the Poston headers because they really look nice but they wouldnt fit with the LT DP which was definately going on to replace my 3" 2pc DP and ported stock exh elbow. If there isnt going to be any difference in performance between the headers (not sure) then I'll just leave it alone.
Sorry so long
