2003 LQ4 6.0 with 07 Trail Blazer intake?

[Big R]

Wondering if anyone can confirm or deny this info. I have an LQ4 out of a 2003 2500 HD. I was considering an intake swap from a 2007 SS Trail Blazer. It is supposed to have a 90mm Throttle body and the high rise intake manifold. I would also swap the injectors and fuel rail from the SS. Will this give me a gain in HP? or too many headaches to bother?

[NorCalAnthony]

That’s actually a fairly common swap on other performance oriented forums and it’s supposed to be worth an extra 20-30+ HP on the 6.0 engines depending on who’s dyno sheet you’re looking at. They flow as well or better than the LS6 intakes that everyone goes nuts for but they’re a lot cheaper and have longer intake runners to maximize low end torque. FYI though the TBSS and other Gen IV truck TB's are 87mm, only the cars got a full 90mm but the couple of times I saw someone try to swap to a 90mm TB there was virtually no gain...

As far as whether or not it's worth it, that's up to you to decide. I was able to find one complete with injectors, rails, TB, etc for only $140 and since I was already doing a new cam and swapping on some 243's I figured why not? Here are a couple of things to look out for if you’re thinking about doing it:

-If your truck is set up for a cable TB you’ll either need to buy a new 90mm 4 bolt cable operated TB or a 3 bolt to 4 bolt TB adapter plate to re-use your existing 78mm TB. Most people aren’t a big fan of the adapter plate option because you wind up limiting the flow of the new intake with the smaller TB.
-If you’re running a DBW TB you’ll need some sort of the harness adapter since the newer TB has different electronics. For your 03 engine you’ll most likely need an X-Link harness adapter from Torquerush that runs $235 but is basically plug and play. There’s a cheaper $50 harness from Caspers (and a few others) that will let you use the 90mm LS2 throttle body but you also need a 99-02 TAC module and both of those can be pricey. Some of the aftermarket harness makers might also be able to build that in to your custom harness if you ask for it. I talked to BP Automotive and they said they could make me a harness that would work with the 87mm TB that came with my intake but I would need the 99-02 TAC module as well which wasn’t a problem because I already had both style TAC modules laying around my garage…
-Fuel injector plugs are also different. You can pick up some plug/harness adapters or new plugs with pigtails to splice in to your existing harness pretty cheap. Or if you're going with an aftermarket harness just request the newer style plug when ordering it.
-The newer intake also has a return-less style fuel rail so if your truck isn’t set up that way you’ll have to figure out something there but there's a ton of different ways to do that and none are all that complicated. Plus if you’re swapping the engine in to an older truck you basically have a blank slate and can do whatever works best/is easiest for your situation.

Lots of information on this can be found online by searching for “TBSS intake swap” but here are a couple of threads I bookmarked back when I was reading up on it:
http://www.gmfullsize.com/threads/ho...e-swap.264691/
http://www.performancetrucks.net/for...ll-nbs-493269/

[Big R]

Awesome info! Thank you!! Sounds like it could get pricey with all the "additional parts" needed. I will need to measure the throttle body I have from the donor motor since it may already be around 80mm. Might be better off to port and polish the heads to gain a bit instead?

[NorCalAnthony]

Really just depends on what all you want to do to the engine and what your budget is. If you’re only looking to do one thing on the relatively cheaper end then I would look at doing a drop-in cam swap from Brian Tooley Racing or Cam Motion. The drop-in cam shafts are made specifically for these truck engines and can be ran with the cheap LS6 valve springs and stock push rods.
http://www.briantooleyracing.com/btr...-camshaft.html
http://store.cammotion.com/ls-truck-camshafts

If you have more money in the budget then doing a port & polish on your heads and milling them a little would be the best overall performance bump but you’d need to do a camshaft swap to really take advantage of them. A lot of companies will custom grind you a cam shaft to match the heads and whatever vehicle you’ll be putting the engine in for the same price as their other camshafts. Of course once you pull the heads off then you need new head bolts and gaskets, plus it’s best to replace the lifters while they’re off, then depending on the engine’s mileage you may want to replace the oil pump, and depending on what cam shaft you get you’ll need better springs and pushrods, and you can see how things start to snow ball lol. With that said Texas Speed is a great place to work with and has some really reasonable head & cam packages as well as gasket & bolt kits for whatever you plan on doing.
https://www.texas-speed.com/p-1159-p...-castings.aspx

That’s why the TBSS intake swap is such a good bang for the buck upgrade. I picked up my complete intake and TB for $140 and was already planning on getting an aftermarket harness so there really wasn't any extra cost beyond that. If you're reworking your donor harness you would need injector pigtails ($20 on ebay) or injector adapters ($50-60) and the x-link ($235) so around $300 give or take on top of what you get the intake setup for and you get a pretty decent performance bump. The benefits of the newer intake are better throttle response (with the bigger TB) and better flow so you can make power easier if you have other supporting mods (cams, heads, etc.). Plus they come with bigger injectors around 33 lbs/hr vs your stock 25 lbs/hr so you’ll have more room to grow if you decide to add things later on.

[Big R]

Thats where I start to question what to do. I should have listed the mods already planned on and started. Here is what I have: 2003 LQ4 6.0, I am swapping the cam out to a Comp Cam with a 208 int./212 exh. lift at 050. Nothing major, just a bit more torque and a little thump. Want to keep the trans stock and not have to change the stall - 4L80E. I took the motor down to the block and have replaced the pistons (stock style just new), polished and balanced the crank, new valves and springs, timing gears and chain. Will use the stock rockers with new bearings and will replace the pushrods for something stronger than stock. The jury is still out on whether to port and polish the heads, not sure what that will cost. I believe they are the 317 truck heads, cathedral style (they are in a box in the back of the truck). I will also do long tube headers and a cold air intake of some type. I was told the stock throttle body is somewhere around 82-87 mm so not sure the few extra mm will be worth it. Having to buy a bunch more harnesses and such doesn't appeal to me right now but if the injectors are better than what I have, it is a thought. The guy wants $300 for the used 07 SS Trail Blazer intake, throttle body, fuel rail and injectors. seems a bit steep when you add in the other stuff I would need. Any thoughts?

[NorCalAnthony]

Definitely sounds like you're off to a good start as far as your plans and parts go but I personally wouldn't go with a Comp Cam, they've had some quality control issues (try Googling Comp Cams failure) and a lot of their cams have aggressive lobe designs that are hard on the valve springs to where even lower lift cams still need high end springs. Those BTR and Cam Motion cams I linked to earlier are around the same intake & duration as what you're already looking at but are designed to work with the stock stall and are a lot easier on the valve train. Plus both of those shops (and some others) will custom grind you a cam shaft that is made specifically for your application (stock stall, CNC'd heads, long tubes, etc) for the same price as their off the shelf cams. Not trying to sway you one way or the other, just pointing out some other alternatives...

If you're having a machine shop install the new valves & springs you mentioned then you may want to see how much they'd charge to mill them while they're in there so you can get a bump in compression. The shops in my area were charging $120-160 for the milling and another $180 for a performance valve job. If you want to step up to a port & polish Texas Speed has one of the best deals around at $750 for their stage 1 CNC porting service which also includes milling them to whatever chamber size you want. A couple other you may want to check out are Advanced Induction and TEA, both are top notch shops with excellent reputations and products. You may want to spend some time going through the forums at ls1tech.com for the more performance oriented questions, there are some awesome knowledgeable guys on here but there's a ton more over there since that's the whole focus.

Not sure where you heard the stock TB's are 82-87mm? Every Gen III engine (car or truck) I've seen has had a 78mm TB that actually measures more like 75mm. The Gen IV truck engines (like the TBSS) have the 87mm TB and the Gen IV cars got the 90mm TB so the size difference is more like 3/8" - 1/2" which is where the extra throttle response comes from.

As far as the price goes, $300 does sound pretty steep. The guy might think he has something really special because it's from a Trailblazer SS but really every 08+ truck came with that same intake... I would try looking on the classifieds sections in some other forums like ls1tech.com or performancetrucks.net or even ebay and see what they're going for. You might be able to find one a lot cheaper or even show the local guy the classifieds ad and see if he'll match the price.