Finally with the holidays, I have some time to update this. Since then, I have received the lightweight Stillen crank pulley and Volant air intake system with Powercore filter, but I've yet to install either and will cover them later. For now, back to the header install.
Overall, with a lift and proper tools, this isn't a bad job. It could be done on the ground, but I would imagine it's a whole lot easier in a shop with a lift and air tools as I was fortunate to have at my disposal. The right side engine mount does not need to be unbolted nor does the engine need to be jacked up...IF...you do not need to save the original manifold heat shield. Removal of the right manifold heat shield was one of the hardest parts of the job! Eventually I found that an Ingersoll-Rand air saw came in very handy as I cut it into sections an removed the shield piece by piece. The insulation creates a lot of dust inside the shield, so you may want to wear a dust mask if you are health conscious. Most of the heat shield bolts will break off, which is not a big idea if you have no plans for the original manifolds other than the trash can. Unbolting the brake line bracket on the frame will give a little play in the brake lines and make the job easier. I would recommend new fenderwell clips as they often break trying to get them out; you'll need about 8-10 of them and you can buy them in bags from Ebay really cheap; it's always good to have a few spares! I also lube the new hardware with copper-grease, aka "copperslip." I have a bottle of Loctite C5-A Copper-based anti-seize which works great in this application and many others, including on brake pad hardware. I did have one issue with the headers: the recess in the flange where the exhaust "O" gasket seats is not as deep as the one on the original exhaust manifold. While bolting the headers to the catalytic converters, it crushed the "O" gasket unevenly and even bent the converter flange. When I noticed the gap, I sealed off the manifold and converter and air tested it to find out it was leaking. I took it apart and replaced the new gasket, which was ruined, with the old gasket coated with Ultra-copper RTV. This was on the right side, which has the original converter with 150,000 miles on it; the left side was replaced at 85000 miles. When I did the left side, I used the original gasket with RTV and it did fit better. All was well until several weeks later; currently, I keep triggering a P0420 catalyst efficiency code for the right-front converter. I'm not sure if it's coincidental that the converter is now failing not long after the header install, or if there is a leak at the gasket. I'll have to look into this. I'll also notify Doug Thorley about it.
The left side was the easier of the two sides, which seams odd because of the steering shaft being in the way on the left side. Someone threw me a cookie in that they cut the heat shield when replacing the left converter, which may have made shield removal a little easier. Whereas the right shield had to go through the wheelwell opening, the left shield could be maneuvered up to the top of the engine compartment. With the shields out of the way, it's really not to bad to get to the manifold nuts; the hardest ones are at the front of the manifold. With the B-pipes/post converters removed, the manifold/catalytic converter assy. pulls out through the bottom. Swap over the headers and re-install. Torque the manifold nut to 22 ft/lbs in proper sequence and install the post converters. In my case, I replaced the post converters with the Doug Thorley mid-pipes. Start the engine and let it run for 20 minutes, then re-torque the header nuts to 22 ft/lbs, again. Reassembly and drive! It is a little louder and I would imagine the removal of the post cats have more to do with the noise than the headers. And while I hate using the "butt dyno" reference, it does "feel" like it has better mid-range power. Obviously, without having access to a dyno for comparison, this is only speculation and/or opinion on my part. You will definitely notice a difference in noise level between what I've done (in combination with the Magnaflow muffler) and the stock system, for better or worse, depending on one's point of view. As I mentioned earlier in the thread, if you prefer a nice, fairly quiet Pathfinder as it comes from the factory, you will not want to do this! It is not obnoxious, but it is noticeable, especially from inside the vehicle.
Remove the wheelwell liner:
View with right liner removed:
Remove brake line bracket:
IR air saw worth weight in gold for this job!:
Bend, cut, remove right shield through wheelwell opening:
Right header installed:
Gap due to poor fit of gasket to new header. Doug Thorley needs to work on this! Maybe an old-style, three-hole, Nissan flange gasket might work better?:
Old gasket used with Ultra-copper RTV:
Right side installed:
Gaskets, new bolts, Loctite C5-A, Ultra-copper RTV:
Left side with liner removed:
Right shield with a little help from a previous converter replacement:
Left side header installed:
Post converters replaced with Doug Thorley B-pipes:
