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.
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