TIMINATOR

The "retarded" turn spoken of is REQUIRED to have as long of a primary tube that headers need to have to enhance the bottom end and midrange torque. The primary tube torque peak is determined by the primary size mostly, but the primary length "rocks" the torque curve around this peak up or down on either side of the peak. The large mass of the 2500 HD prefers more bottom end/ midrange torque at a small expense of upper end power. The SSW headers are available with a 1 3/4", 1 7/8" or 2" primary depending upon the usage required. Big tubes = more top end, smaller tubes are more for heavy towing and fuel mileage. Mine are the 1 7/8" ones that are the best of all worlds for my mix of performance and occasional towing. Note that the regular 454 truck headers are 1 3/4" and are considerably SMALLER than the 454's port, so these have some restriction there (due to the port size needing a formed, square 2" tube,) but work well for all around use on duallys and towing with that smaller engine. Back in the day, somebody made a 1 3/4" header for trucks that was swaged out to 2" at the flange for less restriction, but I have not seen any in about 20 years. The 8.1 uses a smaller, but raised and much more efficient exhaust port than the 454s. For all of the PIA installation hassles and missing, but required, gaskets, the SSW are a well thought out, high quality, expensive, piece. My main bitch is required installation time that is minimized in the instructions, and the lack of supplied gaskets that are NEEDED and mostly dealer parts only. For those of you tuning in late, that would be: 2 1/8" round, high temp header gaskets (same size for all tube diameters due to the flange design), EGR feed tube gasket, and one tail pipe 2 bolt 3" diameter gasket. To SSW's credit, they did include a tube of silicone sealer that implies reusing all of the gaskets, but I opted to only do the job once and replace them. The instructions also omit the possible need for welding and a 2 1/2' length of 3" thick wall, preferably stainless exhaust tubing if you truck has the pre-cats (4 total cats on some trucks, like mine.) Check to see if you have the pre-cats and obtain all of the gaskets before you start the project! After building many dozen sets of custom headers for race and HP street use, I like to think that I have a clue as to what works and what doesn't. TIMINATOR

TIMINATOR

I will be flow bench testing several types of dual 3" inlet/ single 4" outlet mufflers, the stock muffler, and my favorite, a pair of the Dyno Max 3" Super Turbos later this week and will post the results. TIMINATOR

Vindii

I had all the same problems with my Yukon xl install. Except I don't have the second cats. But my pipes where nowhere near lining up and I had to have new mid sections of pipe custom bent. Headers are nice but instructions and pipe fitting sucked.

3500Silverado

I'm seriously considering headers and dual exhaust on my 03 8.1 3500 Silverado. It is RWD, so I'm thinking I may go the route I always have in the past, on older trucks, and just use a good set of passenger car big block headers. I do not have to pass emissions testing here, this is an 11,400 GVW truck, so I do not need the converters. I'm looking for a set of 3" mandrel bent tail pipes, that exit to both sides. Since I'll be doing further upgrades, the headers and complete dual exhaust with a good set of 3" mufflers, either DynoMax or Magnaflow, should be ideal. I'll be modifying an intake to swap on, getting rid of the EGR, adding roller rockers, and having the ECM tuned.

flatblack83

When i was looking for headers for my 03 hd everything i had found was for an 8.1, the stainless works were said to be top notch for the 8.1 and fit super nice. If they fit as good as the 6.0 headers i bought from them you will be happy, they fell into place. Also the 02 positions are in the correct spots.

3500Silverado

There have been a ton of complaints concerning the Stainless Works headers about the bolts being too long, gaskets missing, and O2 harnesses being wrong. Also, I do not want the driver's side wrapping around under the bellhousing. Their headers are made for a 4x4, and I have a RWD truck, I don't need to make compromises like that. For the price, they're not what I want.

I won't have any trouble getting O2 sensor bungs where I need them. Really, my biggest worry about the passenger car headers is clearance for the oil filter (I run a PF932 2 quart filter) and starter. I'll build a set of intermediate pipes to get back to the mufflers. Flowmaster has some 3" tail pipes for later trucks, but I don't know if I can make them fit my truck. I don't really want their muffler, either.