eBay OBX S/S HEADERS FOR GM 2002-2005 4.2L ENGINES: $562.69 + $40 S&H

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I have a Kooks Header I received as part of a trade a trade a while back, already on my truck @MRRSM


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On the general aspects of the appearance, quality, fitment and welding work of OBX Headers:

“...it seems the people on here seem to like them but on other forums they say they are garbage and to stay away from them... but without ever giving any reason. From everything I've been reading from people who purchased it, they were all highly surprised by the Quality and Fitment of the Piece. They say its a Beautifully Welded Header, especially for the price.”

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No one has 100K miles on em like cracked manifolds to know that...
True. But simply not being cast iron will help, and being a header also helps, as both those things allow for more flex. I believe the stress from expansion/contraction rate differences of the dissimilar metals combined with the inherent unforgiving brittleness of cast iron is the primary source of cracked manifolds.

Still... $600 vs $100 is quite a difference, and not sure how many really want to spend that $500 more.
Headers love to rust like manifolds love to crack. They all have their evils.

I just dont see enough advantage to offset cost since you gain no performance over the 08 manifold for far cheaper

There is a maximizer header on ebay for a bit cheaper as well.
Unless you get them ceramic coated inside and out. Should prevent the rust and also keeps heat away. I'm looking at getting my new Caprice headers done as there is so much documented benefits from it, however higher HP is not one of them. Saw info on ceramic coating turbo parts as well.

And here's a set I found for later years.


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I just dont see enough advantage to offset cost since you gain no performance over the 08 manifold for far cheaper
Is the 08 manifold that good? A good header is designed in such a way that exhaust leaving the collector,creates a bit of a vacuum for the next cylinders exhaust,thus helping each other for a better exhaust extraction. rinse and repeat.
In my older days putting a set of headers on a 350 chev sure as hell made a huge difference in power/torque over stock manifolds. Just can't wrap my head around why it wouldn't for the 4.2?


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The '08/'09 manifold flows better than the older design, yes. It's also a bit less prone to cracking quite as soon as the older design as well.
Headers love to rust like manifolds love to crack. They all have their evils.

I just dont see enough advantage to offset cost since you gain no performance over the 08 manifold for far cheaper

There is a maximizer header on ebay for a bit cheaper as well.
Well, if they're stainless like they say, they shouldn't rust. Or at least, not much, if it is cheaper stainless they still will sort of. Also I wonder what the welds are - I've seen cheap "stainless" stuff rust apart at the welds because those are regular steel. That's always fun.

I have regular coated headers on my Camaro and yeah they have some rust just from thermal cycling and dampness. Ideally, whenever I get to a V8 swap, I'll throw stainless headers on it and avoid that issue altogether. Just, $$$$


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@Sparky ... This is an encouraging read from a Camaro site on this very topic... Especially the part about the Excellent Customer Service the OP experienced from OBX:


...and about the specifics of the Stainless Steel and Welds:


OBX Exhaust Header Fits 02-05 Ascender Trailblazer Envoy Rainer Bravada 4.2L

This header increases exhaust flow at higher RPMs to generate more power and maximize performance out of your engine. Get up to 35% better exhaust gas flow by replacing the restrictive and inefficient factory cast log manifolds with these precision built high flow headers. Great fitment, great quality and a great price guaranteed. Extremely competitive pricing that won’t break your bank. Needless to say, this is what you can expect from a vendor of the world's largest automobile OEM manufacture supplier.

  • OBX Racing Sports™ 304 Grade Stainless Steel Header (5pcs)
  • 2002 2003 2004 2005 Chevrole Trailblazer 4.2L I6
  • 2002 2003 2004 2005 GMC Envoy 4.2L I6
  • 2002 2003 2004 2005 Buick Rainer 4.2L I6
  • 2002 2003 2004 2005 Oldsmobile Bravada 4.2L I6
  • 2002 2003 2004 2005 Isuzu Ascender 4.2L I6
  • Mirror Polish Finish
  • Made of 304 Grade Stainless Steel
  • Primary Tube Diameter: 1-5/8" OD
  • Resonated Application
  • OEM Outlet Pipe Connection to Stock Exhaust
  • Flange Thickness: 3/8"
  • Runner Wall Thickness: 16 Gauge (1.5mm)
  • Required o2 Extension Wires
  • Made with 304-grade stainless steel for durability
  • Dual T.I.G. welded for stronger hold
  • CNC mandrel bent pipes for faster smoother exhaust flow
  • Include only the accessories show on the photo
  • All systems are built with the highest quality, care and detail. Don't compromised Quality Assurance is Guaranteed
  • NO installation instruction is included in the kit, we recommend professional installation
  • Flat rate shipping fee only apply to those package shipping within the lower 48 United States
  • If you have any questions, please contact us through eBay message center
  • Limited Lifetime warranty against manufacturer defects (Must fill out and return warranty card with a copy of the receipt and within 30 days of purchase date)
There is NO WAY any Cast Iron Exhaust Manifold can beat the Volumetric Efficiency of ANY Header, Period.
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I think the usual problem in stock exhaust systems is that they are fairly restrictive. GM engineers, for once, did good on the 360/370 system as it is fairly free flowing to the point that headers will only help minimally.

They however did fail in designing said manifolds from cracking :mad:


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This thread got way off-topic, turned into a debate.
Yup...an old debate that was kicked to death years ago and there still is nothing but opinions that the header is better without a tune. You look at tuned manifold and tuned header numbers and no value to header.
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