Quick, name the three most effective components for improving power (not including power adders)?

What did you come up with? Who said displacement? How about carburetion, compression or even headers? With power adders eliminated from the list, what BIG things does that leave us with?

Well, when it comes to making power, the BIG THREE (in my book) include heads, cam, and intake. Not to knock the others (especially displacement), but heads, cam, and intake really are Three Amigos—the terrible trio or even the triumvirate (friends, Romans, countrymen lend me your ears).

While any one of these individually can offer substantial power gains, a cam swap on an LS comes to mind, but get the Anthony, Lepidus, and Octavian of the internal combustion engine working together, and watch Roman Power get built literally in one day! By contrast, having even one of them offer a dissenting voice and its fiddle time at the fiery Nero corral.

LS enthusiasts have been spoiled for decades now, with ample head flow and impressive induction systems, missing only a good cam to make colossal power. What happens when you exhaust the simple cam swap mods on your LS and go looking for the kind of power it takes to forge a new nation? If the abbreviation for that is LS, you are going to need more than Just Anthony, time for Lepidus and Octavian to step up their game!

Key Upgrades

Okay, enough Roman sub-referencing, Hur (okay, last one), here is the situation. We have an aluminum L33 5.3L procured from a local wrecking yard. It had previously been subjected to cam swaps, intake swaps, and even boost. It was, after all, a junkyard LS, so its existence was more or less relegated to life in the dyno colosseum.

In its current configuration, meaning a healthy cam (currently a BTR Red Hot camshaft), FAST LSXR intake manifold, and long tube headers, it made what most would consider more than acceptable power.

Trouble is, we wanted more—a LOT more.

Knowing this, the next round of upgrades saw us thinking ahead. Rather than just install mods that would get us to the next power goal (say, eclipsing 500 hp), we decided to run heads that could take us all the way to 600 hp (if the rest of the SBE 5.3L was indeed up to the task).

Having a set of Trick Flow GenX 220 as-cast cylinder heads at my disposal made my choice easy.

These heads were already being repaired from my Big-Bang Nitrous disaster (Nero would be proud), so we just took the next logical step and had the guys at Brian Tooley Racing give them the once over including porting, milling and a spring package that could take us to even bigger cams and higher rpm with future mods. The icing on the top was a port-matched FAST Intake replete with a faux carbon fiber finish!

The Test Engine Baseline

Because the power gains offered by any single performance component were a function of the test motor and other supporting components, we needed to take a look at our test motor.

Not surprisingly, we started this project (more to come) with a tried and true 5.3L. Unlike the usual (at least for most of us) iron block, run-of-the-mill, base LM7, this test motor hit the octagon mat already swinging. T

his test mule was of the all aluminum variety, meaning in addition to the usual array of aluminum LS aluminum heads (early 6.0Ls notwithstanding), this 5.3L was also sporting the matching aluminum block. The desirable, all aluminum L33 5.3L was certainly a big score from a local wrecking yard. Right from the factory, the H.O. motor featured flat-top pistons (a la 4.8L), high-flow 799 heads and a slightly more aggressive cam than lesser 5.3L motors.

Well worn from both mileage and our own extensive testing, the 5.3L had already been subjected to a Red Hot cam and matching valve springs from Brian Tooley Racing. Additional testing saw the replacement of the stock truck intake with a FAST LSXR intake and 102mm throttle body. When combined with a set of 1-7/8 inch long-tube Hooker swap headers with collector extensions, 80 pound injectors and the Holley HP engine management system, this combo was netted us a solid 481 hp and 417 lb.-ft. of torque (see graph).

Dyno Test Results with Upgrades

Despite the fact that the flow numbers offered by the stock 799 heads (near 250 cfm) suggested they would support even more power, we knew it would make our life easier if we replaced the stock heads with something a tad more sporty!

In fact, we had plans to take this 5.3L combo well past the 500 hp mark toward 600 hp, but we are getting ahead of ourselves here. For this test, we decided to not only provide enough cylinder head to eclipse the 500 hp mark, but to allow us to quest for 600 hp with additional mods. After all, why change heads again if we can just put on the right set now and call it good?

To that end, we installed the milled and ported Trick Flow GenX 220 (no longer) as-cast heads along with the port-matched FAST LSXR intake. After combining them with a set of 0.041 inch thick head gaskets and new (stock) head bolts, the new combo produced some impressive power numbers.

The peak output jumped from 481 hp and 417 lb.-ft. to 512 hp and 440 lb.-ft. of torque, with gains consistent through the tested rev range. In the next test session, with an even bigger cam and short-runner intake, the peak horsepower output would jump to 542 hp, inching us ever closer to the 600-hp mark.

engine dyno chart
Is there really big power to be had from a head swap on a 5.3L? What about if the 5.3L was already an all-aluminum L33 5.3L factory equipped with high-flow 799 heads? To find out, we decided to compare the already good 799 heads to a set of Trick Flow 220 as-cast heads, though the as-cast heads were not left as-cast. In the effort to maximize power, the Trick Flow heads were treated to some additional hand massaging (and milling) by the guys at Brian Tooley Racing. They even port matched the FAST LSXR intake. The reason for this extra effort was that we hoped to take this SBE 5.3L combo well beyond the 500-hp mark with future mods. After running the cammed 5.3L with the 799 heads and FAST LSXR intake, the 5.3L produced peak numbers of 481 hp at 6,400 rpm and 417 lb.-ft. of torque at 5,600 rpm. After verifying the baseline, we swapped over to the TFS 220 heads and port-matched FAST LSXR intake and were rewarded with an increase in peak numbers to 512 hp at 6,800 rpm and 440 lb.-ft. of torque at 5,600 rpm. Wilder cam timing and a short-runner Trinity intake have already taken this SBE 5.3L to 542 hp, so the head swap is just now starting to show its potential. (Dyno Chart/Richard Holdener)
ls engine on a dyno test run
How much naturally-aspirated power can you make starting with a junkyard 5.3L. (Image/Richard Holdener)
ls engine on a dyno
Our test motor started out life as an all-aluminum, (high-mileage) junkyard L33 pulled from a local wrecking yard. (Image/Richard Holdener)
5.3l casting number on an ls engine block
Always a desirable find in a junkyard, the L33 5.3L featured an aluminum block along with higher compression and a slightly more aggressive factory cam profile, compared to the de rigueur iron block LM7. (Image/Richard Holdener)
btr truck norris camshaft in a box
From previous testing, the L33 test mule was equipped with a BTR Red Hot cam that offered 0.617/0.619 inch lift split, a 221/22X duration split and 113 LSA. (Image/Richard Holdener)
799 casting number on an ls engine cylinder head
Finding the L33 aluminum block 5.3L also meant the motor was factory equipped with high-flow (compared to 706/862) 799 heads. These (along with their 243 counterparts) were the highest flowing cathedral port heads offered by GM. (Image/Richard Holdener)
rockers and valve springs in a cylinder head
To prep for the BTR cam upgrade, the 799 heads were treated to valve spring upgrade, though the rockers remained factory stock, no trunnion upgrade. (Image/Richard Holdener)
lsxr intake manifold on an ls engine
Working with the high-flow 799 factory heads and BTR cam upgrade was a FAST LSXR intake manifold. In the sub-7,000 rpm range on an LS (like our 5.3L), the FAST would be tough to beat for average power production. (Image/Richard Holdener)
102mm throttle body installed on an ls engine
The FAST LSXR intake featured a 102mm throttle opening so we saw no reason not to utilize the maximum airflow potential of the intake with a matching 102mm throttle body. (Image/Richard Holdener)
headers on an ls engine during dyno test
The exhaust system consisted of a set of 1-7/8 inch, long-tube Hooker headers feeding collector extensions. (Image/Richard Holdener)
fuel injector rail installed on an ls engine
To ensure plenty of fuel flow to the modified 5.3L motor, we replaced the stock L33 injectors with these 80-pounders from Accel. (Image/Richard Holdener)
holley engine management cpu
Rather than rely on the factory ECU, we dialed in the AF and timing curves on the 5.3L using Holley HP management system. (Image/Richard Holdener)
ls engine during a dyno test
To establish our baseline with the 5.3L, we ran it first with the stock 799 heads and FAST LSXR intake. Equipped as such, the BTR-cammed 5.3L produced peak numbers of 481 hp and 417 lb.-ft. of torque. (Image/Richard Holdener)
casting marks on a trick flow cylinder head
This fancy insignia means these Trick Flow 220 as cast heads came from Total Engine Airflow. These featured the desirable powdered metal valve guides. (Image/Richard Holdener)
cylinder head combustion chamber with valves
To further enhance the power output of the Trick Flow 220 as-cast heads, they were milled 0.030 inch and given some chamber work to further improve the head flow. (Image/Richard Holdener)
valve springs in an ls cylinder head
Knowing we planned to run even wilder cam timing and rpm in the future, BTR equipped the Trick Flow 220 heads with an Ultimate RPM Spring package. (Image/Richard Holdener)
cathedral port on An ls engine cylinder head
The Trick Flow 220 heads originally featured as-cast heads based on ported castings (how they achieved ported flow from as-cast ports), but these heads were repaired from previous damage incurred from the Big Bang Nitrous debacle. After the repair, they were also treated to additional porting from the gang at Brian Tooley Racing. The intake ports flow well over 300 cfm. (Image/Richard Holdener)
exhaust port on a trick flow cylinder head
Naturally the exhaust ports were given the once over as well. What good is huge intake flow if you can’t get it all back out? (Image/Richard Holdener)
trick flow cylinder head on an ls engine
After removal of the stock 799 heads, we installed the Trick Flow 220 heads using new factory bolts and head gaskets (Fel Pro .041). (Image/Richard Holdener)
a pair of metal brackets on workbench
Installation of the factory rockers on the Trick Flow Specialties 220 heads required minor machining of the factory rocker stand locators, as shown. (Image/Richard Holdener)
lsxr manifold on an ls engine
For this test, Brian Tooley even loaned his personal port-matched FAST LSXR intake, complete with carbon fiber wrap. This thing was beginning to look like something other than a junkyard L33. (Image/Richard Holdener)
ls engine on a dyno test
Run on the dyno with the massaged Trick Flow Specialties 220 heads, the aluminum 5.3L produced 512 hp at 6,800 rpm and 440 lb.-ft. of torque at 5,600 rpm. With a short-runner intake and wilder cam timing, these number would eventually be pushed to 542 hp, but the 5.3L is still just scratching the surface of what these TFS 220 heads can support. (Image/Richard Holdener)

Share this Article

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.