How often do you have to replace the gasket? Any install tips?

 

You shouldn't have to replace the gaskets unless you remove the headers again.

 

I installed mine in 2005 and haven't touched them since. Well over 100,000 miles since the install. I think I reused the stock metal gaskets that were on the car.

*Prespray all the nuts and bolts with penetrating oil.
*Be sure you can get the car high enough on jackstands. You'll need some room when working on the rear bank.
*Remove the upper radiator hose and fan assembly but put some cardboard over the radiator. One slip and you'll be replacing it.

One of the challenges is getting the socket on the nuts straight and not stripping them. Have the right sockets in short and deep as well as plenty of extensions. Having a swivel or two helps as too.

Have a grinder handy too. Some of the bolts will snug up close to the pipes and may come down over the weld. You'll want to grind away the weld to clear the nut so it can seat on the flange. If not, you risk snapping the stud or not getting a proper torque.

 

I just did mine. I used oem gaskets too. I installed the Obx ones. Perfect fitment except for rear primary o2 location. The o2 sensor doesn't fit. Have to relocate it out the side instead of straight out the back. Oh I am picking up o2 wire extentions as the wires are a little short too

 

I had mine installed in 2003. Haven't touched them till this year. Section around the flex pipe rusted out. Easy fix for an exhaust shop.

 

Thx for that tip! Hadn't thought of that.

 

keep in mind the you can cut/slice the wiring loom open and UNFOLD the extra wire for the O2 sensors and then wrap it all back up.

I have a Megan racing 2 row all aluminum rad i will be removing it, i will need to mod the brackets since the radiator cooling fan motor's heat shield almost touches the stock header. there is a BIG gap between the rad and core support.

It's good to know i can get OEM gaskets and that they should work fine.

Has any one had a custom Y pipe made for the OBX headers since it's only 2" vs 2.5", i wonder if that matter once the 3.0L is super charged and flowing more air.

 

S/C doesn't seem to care about exhaust. From the dynos I saw there was no gain from 2.5 to 3.0. The Y isn't long enough to matter.

 

so from 2.5 to 3 and no gains are we assuming form 2.0 to 2.5" is no gain either. For some reason 2.0" seems just a wii tad small for a 3.0L. Then again flow and no pre cats may make for that?

for some reason my guts and or feelings seem as such that 2.5" might be the sweet spot.

 

The length of 2 1/8 isn't long enough to hurt flow at all, I'm sure. I mean, people are making good power n/a on these headers. S/C will just force it out.

350Zs make 400whp all day on stock exhaust with cats deleted. Not apples to apples, but I doubt there's more than 1 hp lost unless you're going to build the motor.

 

so it wouldn't be pointless if it step up to a 2.5" all the way to the muffler? idk what size the stock exhaust is. i just know its 2" or around there.

 

Oh lol. I assumed you had a catback. *judging everyone that doesn't*
Stock is 2.25 OD. I bet it still makes 350 whp no problem if you remove the crimp.

I would just get a nice catback, but good luck finding a cattman.

 

If you have the 3.0l, then yeah, go with a 2.5" catback. If you've got the 3.5, go for the 3" BRM catback.

 

Well I meant the new OBX collector is 2" instead of 2.5". Better than pre cats but not optimal. Would seem 2.5" collector would be optimal.

I have 170k miles I plan on pre spraying fasteners as much as possible. Is the 3L header studs or bolts? Anyone break any fasteners?

 

Well, it's a little more than 2 inches. Maybe it's different for the 3l, but mine was about 2.25/2.3 at the collector. I don't know about he 3l, but mine were studs with nuts that fastened the headers onto the studs. I didn't break anything, but I bought all new nuts anyways.

 

Mine is just like yours for my 3.5l

 

Installed my Hotshots back in 05 on my 3.0L

Swapped in a 3.5L in '07. Headers are still on that same 3.5L, swapped my 3.5L into other maxes.. still drive it today

Flex section was replaced with Vibrant Performance's turbo-lined flex like 4-5 years ago with V-band flanges due to our crappy salty NY winters.

Always use the STOCK Nissan gaskets between the headers and the heads.

 

http://www.ebay.com/itm/171986966401

2" collector

 

what would people consider the best fitting and performing headers for 3.5L maxima today?

 

That would be nice to know but, if i'm not mistaken they are no longer sold and or in production.

side note is it just me or is that bit small? is 1.6" primary and 2" collector right? (linked above)

 

Obx is the only ones I could find for my 03.

 

That's definitely small, but it's way better than stock. Obx are the only ones in production for our vehicles to this date. There might be others for your 3L, but OBX are the only for the 3.5L, unless you can find used. They're actually really good in my opinion for the 3.5L, the collector is pretty darn close to 2.5". Depending on how much you're willing to spend, you could always get them custom done. Would probably run you around $1k or so, depending on where you go.

 

im wondering if the old OBXs were closer to 2.5" collector and the news one 2". spec sheet on sale pages say 2". I wonder if it would be cheaper to keep the headers and get a custom 2.5" Y pipe later down the road to fit the OBX headers. i'm gonna have to measure mine.

all the old threads from a long time ago here have broken links. does any one know if that thread showing how to cut the looms and pull out the extra O2 wiring is still around and or if the photos still exist?

 

Not sure about obx but with my Cattmans I didn't have to extend any wiring. I just took the plug off the holder and it had enough length to make it to the firewall header.

 

The this is a known issue with OBXs, some one here made a how to so people woulds top cutting up their O2 wires or harness wires cause the ECU detects that resistance change.

OBXs relocated the O2 bungs, or they used to.

EDIT: Yeah the Catmans are much closer match to stock as far as routing and bung location. short headers longer separated Y pipe.