These are just over a year old - I bought them in September of '06 and had them on my Z71 (so yes they will fit 4wd) and took them off a couple of months ago when I put the truck back to stock. They're listed as fitting 1999-2001, TRUCK/SUBURBAN/TAHOE/YUKON, 4.8L-5.3L, 2/4WD, but again, these were on my 2003. SCIV also runs these if you want to get his input on them. I'm not sure if they'll fit the NNBS or not...? They're in excellent condition and come with the gaskets that were provided by Thorley. I used the gaskets and had no issues with leaking (even with a missing header bolt). These felt amazing on my extended cab Z71 but I need long tubes with my new setup. You won't find a better made header than the Thorley's. They use 14 gauge steel and 3/8" flanges (try to find better). Ask anyone who has them not only about the quality but about how they perform. These currently sell for $1,002 on Thorleys site (obviously overpriced) and $669 on Summit. I'm asking $475 shipped or $450 if picked up in person.
Actual photo:
Stock photo (or click here for a link):
The best way to get rid of your exhaust.
Thorley headers are designed to outflow your stock exhaust manifolds. These headers increase gas mileage and give your engine more horsepower across the entire rpm range. The Tri-Y configuration builds the most power in the middle rpm range, which is great for towing and steep grades. To make these headers last, Thorley made them out of durable 14-gauge mild steel with 3/8 in. thick flanges and 5/16 in. collector rings. To prevent leaks, these headers have an O-ring welded into the flange, in addition to the high-temperature gasket provided.
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02' silverado ext. cb 2wd , 5.3 liter 325c.i. LM7, ported and polished throttlebody with bypass, Jannetty Racing 87 octane dyno tune, cold air intake with custom ram air, Heavy duty built 4l60e with vette servo, Z-pac clutches, "The Beast" Sunshell, transgo shift kit, yukon 4.10 gears with true trac, custom exhaust with Moroso Spiralflow, no cats, MSD 8.5 race wires, NGK TR55's
Originally Posted by farmtruc
