Smitty's '04 GTO

iTrader: (5)

Truck in sig, towing a 6,000 lbs 29' camper, rpm's vary between 2K and 3500 while towing.

The options I'm considering are a set of Thorley Tri-Y's, or a set of American Racing Headers with 1.75" primaries. Either of which with an off-road Y into the factory 6.2 catback.

The Thorley's are 1.875" primaries into 2.5" secondaries into a 2.5" collector. The collector on the ARH's I believe are 3".

The Thorley headers are of mild steel with ceramic coating, the Y-pipe is stainless with ceramic coating. The ARH's are all stainless construction and I would have them ceramic coated.

The Thorley Y is 2.5" into the 3.5" outlet for the factory 6.2 3.5" catback exhaust. The ARH Y is 3" into the 3.5" outlet.

The truck is NOT a daily driver, but does get driven year round on nice days. I live where they use a ****-ton of salt on the roads in winter...



Which direction would you go, and why?


My concerns are: 1.) Thorley's use of mild steel for headers, even if they are ceramic coated, even if they have lifetime warranty.

2.) Loss of low end torque with any 4-into-1 header design.

I'd also consider Kooks or Dynatech, but I like the design of the ARH collector better.

Any input would be appreciated, Thanks!

climb-101

I have never herd any bad stuff about kooks, The others I don't know much about. I would stay away from the mild steel ones. The don't hold up as well and road salt will kill them even faster

CDN SS

iTrader: (1)

I have had the Thorley tri Y on 2 of my trucks and I tow my 6500lb Haulmark car trailer ...... had them on my 2010 CC 4x4 for 5 yrs now I like the low end you get I tow at 2500 in 5th at 70 mph 4.11 rear .... I did have a set of 4 tube 1 3/4 on a 2001 and although not a exact comparison as 5.3 engine has got better but they lost a low end over manifolds .............anyway the Thorley Ceramic coating is crap burned off after 2 yrs my truck is a DD and I live in a similar climate to you but have no rust through or anything like that they seem soiid just look bad FWIW

But you have the 6.2 so more low end torque so I would consider small tube small collector 4 tube stainless headers

Smitty's '04 GTO

iTrader: (5)

Still considering the above. Just wanted to include new info, FWIW.

Thorley uses 14 gauge for their ceramic coated mild steel primary tubes.

Dynatech uses 16 gauge stainless.

Kooks uses 18 gauge stainless.

Don't know, couldn't find out what gauge American Racing Headers uses...

Tig

iTrader: (2)

I loved my Thorleys on my previous Tahoe, I really liked how it was a complete kit. Md length and y pipe all included all ceramic coated with hardware and gaskets. Fit and finish was also great. The coating held up in MA for 5 years, now its in TX. This was on a 5.7 Vortec non LS.

I liked my Kooks as well, beautiful headers. They were on my Ford a long time ago.

Have you thought about Speed Engineering LTs?

Fast355

I have a set of Thorleys on my Express van with the old 5.7 Vortec. I am not sure what the LS truck headers are built out of but the ones for my Express were 14 gauge stainless steel (IIRC advertised T304) with a ceramic coating. I have had the headers on for more than 2 years and drive it about 10-15K a year, about half of that with some kind of trailer hanging from the back. The coating has discolored, but it has not peeled or flake off. I did have a minor fitment issue, but that was due to a cross member difference between my 1/2 ton frame vs the 1-ton frame the headers were built for. The torque difference was instantly noticeable. About the only time I do not tow in 4th (4L80E w/3.73s) is with my 6,000 lbs Jayco 23' travel trailer behind me that is 8' wide and 11' tall. I have had cars on auto transports even a jeep Cherokee on a auto transport trailer and you barely notice them back there at highway speeds even running in OD.

dsmmace

I have kooks 1 7/8's with cats on my truck, there isn't much power increase below 2500 rpm, but above there is where the difference is noticeable. I tow my 4000lb boat without issue after the headers and it will break the tires loose if you are aggressive with the pedal. I do recommend you modify/open up the factory air box after headers with the MIT intake or change to a full intake solution. The most gains I had were in my tune from Blackbear. I also have 3.73's not 3.42 gears like you.

Smitty's '04 GTO

iTrader: (5)

I was under the impression they were made overseas, haven't been considering any of the "el-cheapo" headers like OBX, etc.

Smitty's '04 GTO

iTrader: (5)

One reason I was only considering 1 3/4" primary with the 4-into-1 design, trying to maintain bottom-end. Thanks for the feedback though, it is helpful.

BuyAmericanIron

I am on my fourth set of ARH headers. Never a leak or rattle. Worth every penny. Plus high resale value when you take them off and sell your truck. They will also hold up in your climate.