The question on the table is just how much is an intake upgrade worth?

In reality, that is just one of the questions, as the power gains (if any) naturally come at some cost, so the real (two-fold) question is actually how much for how much?

Given an unlimited budget, we would all have twin-turbo, nitrous assisted, full forged stroker motors with the latest in cylinder head technology and valve train, but the reality is that most of us must be very picky when it comes to choosing performance parts. For the ultimate in low buck, it is hard to beat a cheap turbo, cam, and springs on your typical LS application, but what about those of you that don’t have or want boost, or might possibly add it at a later date?

After all, every junkyard LS is just a Turbo LS waiting to happen.

For the gearheads looking for ways to make power from their 4.8L, 5.3L, or even 6.0L (or you lucky 6.2L folks), the most common upgrade is the camshaft. Add a cam to just about any LS then sit back and marvel at the power gains. The question now is, what do you do after adding a cam? Where is there more power to be had just waiting to be unleashed in your LS? Well folks, one area you can find extra power is in the induction system, most notably the intake manifold.

When you start looking for components that add power to your LS motor, make sure not to forget about the intake manifold! (Image/Richard Holdener)

Comparing LS Intake Manifolds

Are you crazy Richard?

With the possible exception of the original, factory LS1 intake, the remainder of the stock LS intakes are very good. Why should I replace something that already works?

To see how 20 or so of the available intakes fared on a hopped up cathedral port (6.0L) application, check out my channel for a video detailing all the results.

During your visit, make note of how well the FAST LSXR (and FAST LSXRT) did in the comparison. While the factory early truck (most common intake available in the junkyards), LS2, LS6, and (especially) the TBSS intakes all work well, that doesn’t mean there isn’t more power to be had with the proper intake upgrade. In the case of most aftermarket intakes (again, see the intake video), it is not terribly difficult to offer up an intake design that makes a higher peak power number.

The short-runner intakes (Holley Sniper, Hi Ram, Pro Flo etc…) all easily make more peak power or at least more top-end power near the maximum rpm of the engine, but so do these same short-runner intakes sacrifice torque production through much of the curve for the extra peak power. If your plan is to build a high-rpm combo, then these might be something to look at, but what about those hotrodders who want more power without all the losses, or, without resorting to the higher engine speeds?

What about folks who just want to go FAST?

The Intake Comparison 5.3L L33 LS Test Engine

Before getting to the results of our comparison between the FAST LSXR and a run-of-the-mill truck intake, we need to take a look at the test motor. You see, the test motor is every bit as important as the intake when it comes to upgrades. What do we mean by that statement? Well, what this means is that if you were to run a comparison between the factory truck intake and a FAST LSXR (or any other intake) on an otherwise stock 4.8L, the gains offered on would be much less than if you ran the same test on a highly modified stroker 408 (or bigger). The reason is that the stock intake represents much less of a power restriction to the smaller 4.8L than it does on the much more powerful 408.

Basically speaking, give the motor what it needs and you will be rewarded with extra power.

It is also important to point out that this is much more than just simple flow, as many of the short-runner intakes mentioned flow a lot more than the stock intake, but still lose power through much of the curve. Intake design (especially runner length) plays a major part in where the intake adds power. In the case of the FAST intake on our cammed 5.3L, it optimized power in roughly the same rpm range as the stock manifold, it just made a lot more.

Now that we understand this, we can get to the test motor and results. The test motor was an aluminum L33 sourced from a local junkyard.

Where do all the best LS test motors come from? Like most of my test mules, this all-aluminum L33 5.3L was sourced from a local salvage yard. Sure, it was greasy, grimy, and high mileage, but the L33 has proven to be a solid performer! (Image/Richard Holdener)

Though they are rare, the aluminum 5.3L L33 motors offered a lightweight block, more compression than the more-common, iron LM7, and the desirable (to many), big-valve, 243/799 heads. For our test, the high-mileage L33 was equipped with a cam upgrade in the form of a Red Hot cam from Brian Tooley Racing.

The aluminum L33 truck motor came factory equipped with these (desirable) 799, cathedral port heads. (Image/Richard Holdener)

The Red Hot cam offered a 617/619 lift split, a 221/24X degree duration split, and 113 degree LSA (see the full cam card here). The test mule was also equipped with a valve spring upgrade, 1-7/8 inch, long-tube headers and collector extensions and a Holley HP management system to control the 80 pound injectors.

To help the little 5.3L make power, the stock cam was replaced with a healthy grind from Brian Tooley Racing. The BTR Red Hot offered a 617/619 lift split, a 221/24X degree duration split, and 113 degree LSA. (Image/Richard Holdener)

LS Intake Comparison Dyno Test Results

After dialing in the 5.3L combo with the stock truck intake and throttle body, the cammed 5.3L produced peaks of 456.5 hp at 6,300 rpm and 411.7 lb.-ft. of torque at both 5,100 & 5,200 rpm.

After installation of the FAST LSXR intake and matching 102mm throttle body, the peak numbers jumped to 480.7 hp at 6,400 rpm and 416.7 lb.-ft. at 5,600 rpm.

Measured peak to peak, the FAST LSXR intake increased the power output of the cammed 5.3L by 24 hp, but it is important to note that the most of the gains came past 5,000 rpm. Below that rpm, the two intakes traded one or two lb.-ft. of torque back and forth, likely something you would not feel from behind the wheel, but your time slips will definitely reflect the extra power offered by the intake upgrade.


Head flow is awesome, as is a suitable cam profile, but when you go looking to make more power with your junkyard 5.3L, don’t forget the intake manifold. Case in point, this aluminum 5.3L L33 test mule. Scored from a local junkyard, the L33 offered a slightly more aggressive cam, higher compression, and 799 heads compared to the milder (iron) LM7 version. Not content with the stock performance, we opted to run our induction test in slightly modified form, after equipping the 5.3L with a BTR Red Hot cam & long-tube headers. Of course the combos were dialed in with the Holley HP management system. Run first with the stock (early) truck intake and throttle body, the cammed 5.3L produced 456.5 hp at 6,300 rpm and 411.7 lb.-ft. of torque at both 5,100 & 5,200 rpm. After upgrading the induction system to a FAST LSXR and matching 102mm throttle body, the peak numbers jumped to 480.7 hp at 6,400 rpm and 416.7 lb.-ft. at 5,600 rpm. The intake upgrade was worth 24 hp on the 5.3L, with most of the gains coming past 5,000 rpm. (Dyno Chart – Richard Holdener)
For this test, the L33 5.3L was equipped with a single beehive spring upgrade from Brian Tooley Racing. The beehive springs were combined with stock (high mileage) rockers and hardened (7.45) pushrods from Comp Cams. (Image/Richard Holdener)
First up was the factory intake that came stock on the L33. The original truck intake has proven itself a solid performer time and time again. (Image/Richard Holdener)
Feeding the 78mm opening on the factory truck intake was an equally sized factory throttle body. (Image/Richard Holdener)
To ensure adequate fuel delivery to both of the intakes on our test, we equipped the test motor with 80 pound Accel fuel injectors. (Image/OnAllCylinders)
All testing was performed with a set of 1-3/4 inch, long-tube QTP headers feeding a pair of 18-20 inch collector extensions that help low-speed torque but sacrifice no peak power. (Image/Richard Holdener)
Tuning each of the induction combos was a Holley HP management system. The timing and fuel were dialed for each intake and both responded to identical maximum (29.8 degrees) timing values. (Image/Richard Holdener)
Run with the factory truck intake, the cammed 5.3L produced peak numbers of 456.5 hp at 6,300 rpm and 411.7 lb.-ft. of torque at both 5,100 & 5,200 rpm. (Image/Richard Holdener)
After running the truck intake on the cammed L33, off it came to make room for a much more powerful induction system.(Image/Richard Holdener)
For a previous test with a Ford Eaton supercharger (video available on Richard Holdener’s YouTube channel), the valley cover received button head retaining bolts to help clear the bottom of the FAST intake. (Image/Richard Holdener)
We replaced the factory truck intake and throttle body with a FAST LSXR intake. In previous testing (many times), the FAST intake has also proven itself much more powerful than the truck offering. (Image/Richard Holdener)
Working with the 102mm opening in the FAST intake was this matching 102mm Big Mouth throttle body. (Image/Richard Holdener)
Fast also supplied the necessary 75 pound fuel injectors and billet aluminum fuel rails. (Image/Richard Holdener)
Run once again with the FAST LSXR intake and throttle body, the power output of the all-aluminum 5.3L jumped from 456 hp and 411 lb.-ft. to 480.7 hp at 6,400 rpm and 416.7 lb.-ft. at 5,600 rpm. While peak torque shifted slightly from 5,200 rpm to 5.600 rpm, peak power changed by just 100 rpm! (Image/Richard Holdener)

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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.