How much power is a TBSS intake worth over the O.G. Gen. 3 Truck intake?

Seems like a test should be straight forward enough, just grab a test motor and run a couple of quick intakes on it, bingo, bango, bongo! In reality, there is always much more that goes on behind all the simple test data, and this test is a perfect example of that.

Before we look at that, let’s talk about intake hierarchy, meaning which is the best factory intake? Before we pick the top dog, we need to specify which factory intakes were are talking about, since there are three distinct intake designs in the LS family: the cathedral port, the rectangular port (LS3), and the tall port (LS7).

For our needs, we are limiting the discussion to cathedral port intakes, since neither the LS3 nor the LS7 intakes match up to the cathedral port heads (and FYI, the LS3 intake with adapters on a cathedral port head is a terrible choice).

For factory cathedral port intakes, the top contenders are the factory LS6 and the unique manifold fitted on the TrailBlazer SS (which we causally refer to as the “TBSS”), with back-to-back testing indicating the TBSS being top dog, but know the tall design is often a no-go on some low-hood applications (thus LS6).

man fitting trailblazer SS intake onto an engine
How much power is the TBSS intake worth over the early Gen. 3 Truck intake on a cammed 6.0L? (Image/Richard Holdener)

Most should know that the TBSS is the best performing (factory) cathedral port intake, but just how much better is it than the original truck intake?

To find out, we ran both on a 6.0L test motor—with not one, but two different cams. We did this to illustrate that the gains offered by the intake are not cam specific. Before we could run our test, we needed to address some deficiencies in our test motor.

The 6.0L LQ4 was a gift from a reader (Thanks Mike!), but before running this test, I decided to take it apart and add ring gap, since the motor was already in (headless) short block form. Everything to properly assemble the motor was there, it had been previously disassembled to illustrate what makes a motor run to a local shop class. After disassembly for ring gap, we found that not only were all of the oil rings locked in place (unable to rotate) from carbon build up (very common on high-mileage motors), but also several of the top and second rings were likewise locked in place.

Some clean up with gas freed up the stuck rings (no piston damage) and then we proceeded to add some boost gap (to 0.028″). The stock 317 heads received the old “Razor-Blade Rebuild” including lapping compound and the drill on the exhaust valves. The heads also received a BTR 0.625″ lift valve spring upgrade in anticipation of our dual cam swap.

To illustrate the gains offered by the two intakes, we first equipped the LQ4 with a Low Buck Truck (LBT) cam from RichardHoldenerPerformance. The LBT cam has been tested many times and gains are usually in the order of 60 hp over a stock LM7/early LQ4 cam. For this intake test, we just started with the LBT cam and plopped the motor on the dyno with the Truck intake and stock truck (manual) throttle body. For dyno use, the LQ4 motor was also equipped with 1-7/8 inch dyno header with collector extensions, a Meziere electric water pump and a Holley HP engine management system controlling FIC 1,000cc injectors (sized for later boost).

Run first with the Gen. 3 Truck intake, the LBT-cammed LQ4 produced 439 hp at 5,600 rpm and 453 lb.-ft. of torque at 4,200 rpm.

After replacing the Gen. 3 Truck intake with the TBSS intake, we installed a 90mm FAST throttle body. The original idea was to also include a test with a 3-to-4 bolt adapter/reducer to allow installation of the same factory truck (78mm) throttle body on the TBSS, but it didn’t arrive in time for testing. Given the power output, we doubt the throttle body size was responsible for the gains, but another test will help illustrate if this was indeed the case.

The TBSS and FAST throttle body improved the power output of the LBT-cammed 6.0L to 452 hp at 6,100 rpm and 457 lb.-ft. of torque at 4,400 rpm (gains of 13 hp and 4 lb.-ft.).

After running the LQ4 with both the Truck and TBSS intakes using the Low Buck Truck cam, we replaced the LBT with the slightly larger Truck Plus cam. The Truck Plus cam offered higher lift (0.585 vs 0.552 in.), increased duration (219 vs. 212 degrees) and a wider LSA (111 vs. 107.5 degrees).

Testing has shown the cam upgrade to be worth 15 hp or so above 5,000 rpm, with the smaller LBT cam offering better torque below 5,000 rpm (as much as 30 lbs.-ft.). For our needs, we just wanted to compare the two intakes again with a different cam profile.

After installation of the Truck Plus cam, the LQ4 was once again run with the Gen. 3 truck intake to the tune of 453 hp at 6,000 rpm and 448 lb.-ft. of torque at 4,500 rpm (14 hp over the LBT cam with the Truck intake).

After installation of the TBSS intake and FAST throttle body, the power output increased to 465 hp at 6,200 rpm and 457 lb.-ft. of torque at 4,600 rpm. The TBSS intake improved the power output by 12 hp and 9 lb.-ft. of torque, once again illustrating its superiority over the Gen. 3 Truck intake.

If your application can fit the taller TBSS intake, there is no better factory cathedral port intake.

TBSS Intake test dyno chart
After disassembly, fixing a couple of issues and adding ring gap to the high-mileage LQ4, we started our test to compare the early factory (Gen. 3) Truck intake to the TBSS intake. For this test, the 6.0L was first equipped with a Low Buck Truck cam from RichardHoldenerPerformance.com. That cam offered 0.552 lift, a 212/22X degree duration split and 107.5 degree LSA. The test motor was configured on the dyno with long-tube headers and a factory throttle body feeding the truck intake. All testing was run with a Holley HP management system. Run with the truck intake, the cammed LQ4 produced peak numbers of 439 hp at 5,600 rpm and 453 lb.-ft. of torque at 4,200 rpm. After installation of the TBSS intake and manual 90mm Fast throttle body (matching the 90mm opening in the TBSS intake), the power output jumped to 452 hp at 6,100 rpm and 457 lb.-ft. of torque at 4,400 rpm. The TBSS intake was worth an additional 13 hp over the truck intake and improved power from 3,700 rpm on up, with a slight loss in torque below that point. (Dyno Chart/Richard Holdener)
final stock vs TBSS Intake test dyno chart
After running the intake comparison between the Truck and TBSS intakes on the LQ4 with the Low Buck Truck cam, we swap it out for a slightly larger Truck Plus cam. Prior to testing the intakes with either cam, the 317 heads were equipped with a valve spring upgrade from Brian Tooley Racing. The .625-lift beehive springs allowed more than enough clearance for the 585-lift Truck Plus cam (585 lift, 219/225 degree duration and 111 degree LSA). Run first with the larger cam and early Truck intake, the cammed LQ4 produced 453 hp at 6,000 and 448 lb.-ft. at 4,500 rpm. After installation of the TBSS intake, the peak numbers jumped to 465 hp at 6,200 rpm and 457 lb.-ft. of torque at 4,600 rpm. On this combo, the TBSS intake was worth 12 hp and 9 lb.-ft. of torque, though there was less of a loss down low compared to the truck intake with this (Dyno Chart/Richard Holdener)
6.0L LS casting mark on an engine block
The test motor was a high-mileage, iron block 6.0L LQ4. (Image/Richard Holdener)
a bunch of old pistons on a workbench
Prior to testing, the 6.0L LQ4 was disassembled to add ring gap for future boost testing, but we found a few stuck rings that would have certainly limited power production. (Image/Richard Holdener)
close up of ring gap on a piston ring
After cleaning and freeing up all the rings, we increased the gap (of the stock rings) to 0.028″ in anticipation of later running boost. (Image/Richard Holdener)
man holding a camshaft
Because the stock LQ4 cam had one damaged lobe (the lifters were fine), we installed a Low Buck Truck cam from RichardHoldenerPerformance.com. The cam offered 0.552 lift, a 212/22x degree duration split and a 107 degree LSA. (Image/Richard Holdener)
combustion chamber in an LS engine cylinder head
The 6.0L LQ4 came factory equipped with 317 heads. These heads were retained, but not before a little touch-up work. (Image/Richard Holdener)
close up of valve lapping on an old cylinder head
The heads and block were treated to the old Razor-Blade Rebuild (scratching off the gaskets with a blade). We even used some lapping compound and a drill to seat the pitted exhaust valves.
(Image/Richard Holdener)
valve springs installed on a ls cylinder head
Prior to running the intake test, we upgraded the 317 heads with a set of 0.625″ lift beehive springs from Brian Tooley Racing. The spring upgrade allowed us to run both the 0.552″ and 0.585″ lift cams on the test motor. (Image/Richard Holdener)
Fuel injector rail close up
Thinking ahead to boost, we equipped with the motor with 1000cc FIC injectors. For this NA 6.0L application, the 50 pound (flex fuel injectors) would be a very cost-effective alternative. (Image/Richard Holdener)
a Box of ARP Head Studs on an ls engine
Once again thinking boost, we replaced the factory head bolts with a set of ARP head studs. (Image/Richard Holdener)
Brian Tooley LS Valve Cover with Coil Packs
For dyno testing, especially with boost, we like to upgrade the valve covers (like these BTR valve covers) that allow ample crankcase ventilation. (Image/Richard Holdener)
man adjusting air fuel ratio map at a computer
All testing and tuning were run with the Holley HP management system. The ECU made quick work of dialing in the AF and timing curves. (Image/Richard Holdener)
Stock Truck style LS Engine Intake Manifold, installed
First up on the test motor was the early (Gen. 3) Truck intake. Testing has shown it to be a solid performer, especially since it comes free on your average junkyard motor. (Image/Richard Holdener)
close up of throttle body on an LS engine
The Truck intake was run with a matching factory throttle body. (Image/Richard Holdener)
ls engine with truck manifold on dyno test pull
Run on the dyno with the Truck intake, the cammed 6.0L LQ4 produced peak numbers of 439 hp at 5,600 rpm and 453 lb.-ft. of torque at 4,200 rpm. (Image/Richard Holdener)
trailblazer SS (TBSS) intake manifold installed
After running the Truck intake, we replaced it with the TBSS intake. (Image/Richard Holdener)
close up of throttle body on TBSS intake manifold
The TBSS intake featured a 90mm throttle opening, so we equipped the TBSS with a FAST 90mm (manual) throttle body. (Image/Richard Holdener)
ls engine with TBSS intake on dyno test run
On the dyno, the TBSS upped the power ante to 452 hp at 6,100 rpm and 457 lb.-ft. of torque at 4,400 rpm (gains of 13 hp and 4 lb.-ft.). After swapping to the larger Truck Plus cam, the same TBSS intake swap netted gains of 12 hp and 9 lb.-ft.! Regardless of the cam, the TBSS just works better. (Image/Richard Holdener)

Keywords
intake manifolds , LS Engine , TBSS
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Author: Richard Holdener

Richard Holdener is a technical editor with over 25 years of hands-on experience in the automotive industry. He's authored several books on performance engine building and written numerous articles for publications like Hot Rod, Car Craft, Super Chevy, Power & Performance, GM High Tech, and many others.