I plan to install some long tube headers (ASM or TOG) or Tri-Y on my 2000 Yukon XL (K2500/LQ4 Vortec 6.0) Does anyone have experience (perhaps a dyno graph of before and after) on any these headers?

Thanks in advance.

 

They are not out yet for the 6.0. At least that is what Thorley tells me. I dont see a difference in the 6.0 and the 5.3, since they are not a direct bolt on application anyway. If you get them and they work our for you, let me know. I have been waiting patiently for months.

P.S. Did you loose any low end with that cam you installed?

 

First the headers. There is a recent development for the Vortec 6000 engine. They are planning to prototype the 312Y in late November and the production headers should be out in 8 to ten weeks after the prototyping. If you're interested, call Randy Miller at Thorley in the tech department and he can probably put you on a waiting list. The difference between the 310Y (developed for the 4.8/5.3 engine) and the 312Y is in the exhaust pipe transition to the catalytic converter(s). The smaller displacement engines use a Y tube to transition into a single cat. My Yukon and your HD have dual 2.8 to 3 inch pipes all the way through to aft of the muffler before they Y together. We also have dual cats that are staggered to be the same approximate distance from each exhaust manifold collector. I plan to install the 312Y headers rather than the long tube assuming that they are developed as planned.

Secondly, regarding low end torque and my cam. There may be a tiny loss in torque from idle to 1300 RPM's, but I don't think that I've lost anything although I did not dyno the truck before or after. Under even normal acceleration, much less WOT, the truck is noticeably spunkier. I use less throttle application in daily driving and am frequently surprised how quickly I'm going through 45 MPH in a 30 zone. The power gain above 2,000 through 5,800 is excellent and I can't wait to work with the induction system and the headers. I have some additional comments on the cam/valve spring change at https://ls1tech.com/forums/showpost....2&postcount=48

 

I have continued talking to the folks at Thorley about the development of the 312Y headers for the 6.0 L. However, they have decided to make them shorty headers instead of the Tri-Y long tubes, so I decided to order the 310YC which is the ceramic version for 49 states (federal emissions). They also make a version with air injection which is CARB approved in California.

I got them last week and I will be installing them in the next two weeks. I decided in the mean time to post some pictures that I took of them because I think that they are less well known than the TOG's or ASM's and just as good performance wise.

When I do the install, I'll take some more pictures and write up a summary of the performance gain.

 

Well, I installed the Thorley 310YC (Tri-Y, Ceramic Coated) headers the week before Christmas with the help of my 24 year old son, David. Nothing hard or surprising. They fit like a glove on the engine and I had no routing problems (interference, etc.). However, the headers are designed for a 1500 series truck with a manual or 4L60E transmission. My truck is a K2500 with the 4L80E and larger pipes. The only issue was adapting the passenger side header collector to the exhaust pipe. The right side header collector is kicked up about 15 degrees too much and the exhaust shop had to make a jog in the pipe.

It took David and me about 10 hours to install the headers and it took the exhaust pipe about one hour and 20 minutes to fabricate and weld the pipes. They charged $75.

The Thorleys have improved my torque across the band from idle to the shift point at 5,600. I haven't done a dyno yet, but the headers have really enhanced the performance of the cam/cold air intake/Hypertech combo. My 0-60 times have gone from 10.6 sec (stock) to 8.8 sec (with the total package). This on a truck that weighs 6,100 pounds! I have posted some installation pictures at http://community.webshots.com/user/sbryant2100.

I welcome your comments.

 

Looks like a quality product.
I wonder if that little jog in the exhaust, right after the header is hurting any power?

 

do they sell the long tube y design for the 4.8/5.3?

 

I doubt that the jog hurts the performance much at the CFM I am running. I doubt that the torque/HP gain would be more than 2% if the pipe were straight at the very most.

The pipes are actually designed for the 4.8/5.3. They retain the factory cat(s) and Y tube. The 6.0 factory exhaust mainifolds are the same as the 4.8/5.3. After the exhaust pipe mating flange, the 6.0 factory exhaust pipes are about 2.25" in diameter for about 4 lineal inches then they step up to about 2.75" in diameter. That's the only real difference. The short answer to your question is yes, they do sell these headers for the 4.8/5.3. Talk to Randy Miller at Thorley with your questions. Their phone number is on their web site at thorleyheaders.com

 

Looks nice, glad it worked out for you!

As a suggestion for future people who do this, you could probably cut the flange on the collector and angle it down as an option. Don't think this would really have any negative effects, but I could always be wrong.