Best Camshafts for Performance: Gen IV LS Engines

One of the most misunderstood performance components on any LS engine has to be cam timing. The difficulty is only compounded when you add things such as nitrous oxide, turbos, or superchargers. From an anatomical standpoint, the camshaft can be likened to the brain because the cam profile determines how effectively (when and where) breathing takes place.

The camshaft is one of the major determining components of the effective operating range of the engine. Of course, cam timing must be combined with the proper intake manifold, head flow, and primary length on the exhaust for optimum operation over a given RPM range, but the right cam can almost determine the character or personality of the engine. Stock or ultra-mild aftermarket cams provide a dead-smooth idle, while more radical grinds can transform that mild-mannered LS engine into one radical ride.

The factory LS3 is a common upgrade for 4.8 and 5.3 applications because those lesser LS engines were equipped with the mildest factory cams ever offered. Of course, the high-performance LS7 was factory equipped with the most powerful cam ever offered on an LS, but the stock stuff is just begging to be replaced.

 

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The LS3 and LS7 are fantastic engines, offering an impressive combination of power, reliability, and even fuel mileage. Another area where they excel is how well they respond to performance upgrades, especially camshafts. These factory performance engines respond so well to wilder cam timing because they have everything else required to make power, including displacement, intake, and head flow. All that is lacking to dramatically improve the power output of a typical LS3 or LS7 is cam timing.

With the factory heads and intake already capable of supporting more than 600 hp (700 hp on the LS7), mild cams are definitely the limiting factor. Given this situation, cam upgrades for LS applications have become hot sellers. Plop just about any cam in an otherwise stock LS and watch the power soar. I have seen power gains of 65 to 70 hp from a simple cam swap on an otherwise stock LS application. The gains can be even greater higher in the rev range.

There is, of course, a limit to how wild you can go with cam timing on an otherwise stock LS (3 or 7) engine. Although the LS duo certainly responds to more aggressive cam timing, two limitations are inherent in the stock combinations. First, stock valve springs were designed for stock cams and are, therefore, insufficient for performance use. From available valve lift and RPM potential standpoints, spring swaps are not just a good idea, they should be considered mandatory for most cam upgrades on an LS3 or LS7.

The other limiting factor in terms of cam timing on a stock LS3 or LS7 application is available piston-to-valve clearance. Although lift plays a minor role, the real culprit in piston-to-valve clearance is duration (how long you hang that valve open). Each successive increase in duration (the intake hits before the exhaust) decreases the available clearance. Cams that exceed 230 degrees of intake duration should always be checked, especially if they were ground with a few extra degrees of advance.

One of the most common questions regarding camshafts is which one is right for your LS combination. The term “right” here obviously has different meanings for different people, so choosing the so-called right cam can be difficult for even cam experts. The difficulty comes not in the technical nature of cam timing or profiles, but in deciphering exactly what you want. This becomes even more difficult when you are unsure.

Asking enthusiasts what cam they want is a little like asking them how much power they want. The problem is that they want as much power as possible and they also want a factory-smooth idle, 50 mpg, and maintenance-free operation. It goes without saying that it is not possible to combine all of those elements. Obviously that is a lot to ask of any camshaft and, ultimately, trade-offs become necessary. The question then becomes how many of the trade-offs you are willing to accept in your quest for power. Luckily for LS3 and LS7 owners, it doesn’t require much in the way of cam timing to make a major difference in power.

 

Test 1: Stock LS3 vs Comp Cams 281LRR on a Modified LS3

Cam swaps are popular for the LS family, especially the LS3, for good reason. Nothing adds power to an LS3 like a cam swap. Short of power adders or a stroker engine, no modification equals the power gains offered by a cam swap. This is because an LS3 already has sufficient displacement, intake, and (especially) cylinder head flow to make serious power. The only thing missing from the combination is cam timing. Add the right cam to an LS3 and watch the power needle climb.

The power gains are even more impressive when you further increase the power potential with ported LS3 heads such as the ones from Chevy Performance run on this LS3 crate engine. Chapter 2 illustrated that an added ported head to a stock engine offers very little in the way of extra power, but adding a cam to a combination with ported heads shows big gains.

This test engine was a GM Performance LS3 crate engine from Gandrud Chevrolet upgraded with GM Performance CNC L92 heads, ARP head studs, and a manual throttle body. The LS3 also featured Lucas 5W-30 synthetic oil, long-tube headers, and a Holley Dominator EFI management system.

Run first with the stock LS3 cam, the LS3 produced 503 hp at 5,500 rpm and 497 ft-lbs of torque at 4,600 rpm. The GM Performance L92 heads were supplied with stock LS3 springs, so it was necessary to install a set of dual springs from BTR to test the cam. After replacing the stock LS3 cam (and springs) with the Comp 281LRR cam (.617/.624 lift split, 231/239 duration split, and 114 LSA), the peak numbers jumped to 569 hp at 6,500 rpm and 522 ft-lbs of torque at 5,200 rpm. There was little change in power below 4,000 rpm, but the gains increased thereafter with engine speed.

 

 

 

Stock LS3 vs Comp Cams 281LRR on a Modified LS3 (Horsepower)

Stock LS3 Cam: 503 hp @ 5,500 rpm Comp 281LRR Cam: 569 hp @ 6,500 rpm Largest Gain: 70 hp @ 6,400 rpm

The most amazing thing about the power generated by the Comp cam swap was not that it added a ton of power (it did), but that the amazing gains came with no loss in power at 3,000 rpm. The gains from the cam swap increased with engine speed and peak with 70 hp at 6,400 rpm.

 

Stock LS3 vs Comp Cams 281LRR on a Modified LS3 (Torque)

Stock LS3 Cam: 497 ft-lbs @ 4,600 rpm Comp 281LRR Cam: 522 ft-lbs @ 5,200 rpm Largest Gain: 57 ft-lbs @ 6,100 rpm

What I like about adding a cam to an LS3 combination is that the amazing top-end power gains come with no penalty in low-speed torque. In fact, torque gains occurred just below 4,000 rpm and increased with engine speed. Larger cam profiles start to trade off low-speed torque for possible gains in peak power.

Test 2: Stock LS3 vs BTR Stage IV on an LS3

Adding just about any performance cam (and springs) to a stock LS3 is going to get you a lot of extra power, but adding the right cam can offer even more. To illustrate the gains possible with a cam-only upgrade on a stock LS3, I installed the Gandrud Chevy LS3 crate engine on the dyno and treated it to a Stage IV cam from BTR. Right at the limit of available piston-to-valve clearance, the Stage IV cam was the perfect candidate to work with the stock LS3 heads.

Remember, even in stock trim, an LS3 has an excess of cylinder head flow. The stock heads are capable of supporting nearly 700 hp on the right application (see Chapter 2), so the only thing missing in the combination is cam timing. It is also important to remember that not all cam-only upgrades are created equal and that most (like this one) must be combined with appropriate valve springs (these came from BTR as well).

The Gandrud crate LS3 was installed on the engine dyno and run with the stock cam using long-tube headers, a Holley HP management system, and Lucas oil. Also present was a FAST (manual) throttle body, Meziere electric water pump, and K&N oil filter. Run with the stock LS3 cam, the LS3 produced 496 hp at 5,800 rpm and 488 ft-lbs of torque at 4,700 rpm.

Replacing the stock cam with the Stage IV from BTR also required swapping out the single-bolt, 4X cam sprocket for a three-hole, 4X version. After installation of the new cam, the power output jumped to 570 hp at 6,500 rpm and 522 ft-lbs of torque at 5,300 rpm. Not only was peak power production way up, but the cam swap netted torque gains all the way down to 3,000 rpm. Below 4,500 rpm, the BTR cam offered an extra (and consistent) 20 to 25 ft-lbs of torque, but this number increased substantially above 4,500 rpm.

 

Stock LS3 vs BTR Stage IV on an LS3 (Horsepower)

Stock LS3 Cam: 496 hp @ 5,800 rpm BTR Stage IV Cam: 570 hp @ 6,500 rpm Largest Gain: 90 hp @ 6,600 rpm

As much as I liked the huge peak power gains (74 hp) and extra 90 hp at 6,600 rpm, I also liked the fact that the BTR Stage IV cam offered gains down low. You know you have made the right cam choice for your application when you get huge power gains with no trade-offs in low-speed torque.

 

Stock LS3 vs BTR Stage IV on an LS3 (Torque)

Stock LS3 Cam: 491 ft-lbs @ 4,700 rpm BTR Stage IV Cam: 522 ft-lbs @ 5,300 rpm Largest Gain: 67 ft-lbs @ 6,400 rpm

Adding as much as 90 hp to an LS3 is an amazing thing, but it is the extra 25 ft-lbs down at 3,700 rpm that will be used more often in daily street driving. The extra 20–25 ft-lbs of torque up to 4,500 rpm will be most helpful in getting this LS3 up on the cam.

 

Test 3: LS9 vs LJMS Stage 2 Turbo on a Short-Stroke LS3

As you saw in the first two tests, cam timing is important for LS3 applications, but nowhere is it more important than on a turbo application. Spool-up of the turbo is a function of the power output of the engine at the desired spool RPM. The greater the power output, the quicker the spool-up. Things that can alter spool-up include displacement, cam timing, and intake design.

Small-displacement engines have more difficulty spooling up turbos (especially large ones), as do wilder cam timings (that may sacrifice low-speed torque) and short-runner intakes (that also reduce torque production lower in the rev range). This test illustrated the power gains offered by a cam swap on a short-stroke, LS3 turbo combination equipped with a short-runner, Holley Hi-Ram intake and large, 76-mm Precision turbo (meaning it had three strikes against it in terms of spooling). Thus, cam selection was even more critical on this engine than a stock LS3.

The short-stroke turbo engine featured an aluminum LS3 block equipped with a 4.8 crank, 6.30-inch forged Lunati rods, and custom JE pistons. The combination also included Total Seal rings, TFS Gen X 255 heads, and a Holley Hi-Ram intake (with 102-mm FAST throttle body). Rounding out the package was a Moroso oiling system, ATI dampener, and custom DNA turbo manifolds. The manifolds fed a single Precision 76-mm turbo, a CX Racing ATW intercooler, and TurboSmart 45-mm Hypergate waste gates.

The engine was first run (on the waste-gate springs) with an LS9 cam. So equipped, the turbo combination produced 697 hp and 598 ft-lbs of torque. After installation of the LJMS Stage 2 Turbo cam, the power numbers jumped to 733 hp and 621 ft-lbs of torque, but the real story is how much extra low-speed torque the cam swap offered. The gains would be even greater had I elected to equalize the boost pressure because the boost dropped by .5 psi after the cam swap (I ran it on the spring).

 

 

LS9 vs LJMS Stage 2 Turbo on a Short-Stroke LS3 (Horsepower)

LS9 Cam: 697 hp @ 6,900 rpm LJMS Stage 2 Turbo Cam: 733 hp @ 6,600 rpm Largest Gain: 34 hp @ 6,600 rpm

In some instances, a cam swap offers substantial power gains at higher engine speeds. Replacing the most powerful factory cam available (the LS9) with an LJMS Stage 2 turbo cam resulted in peak power gains as well as gains through the entire rev range. The cam swap also dropped the boost pressure by as much as .5 psi. More power with less boost is always a good thing.

 

 

LS9 vs LJMS Stage 2 Turbo on a Short-Stroke LS3 (Torque)

LS9 Cam: 598 ft-lbs @ 5,600 rpm LJMS Stage 2 Turbo Cam: 621 ft-lbs @ 5,500 rpm Largest Gain: 61 ft-lbs @ 3,800 rpm

The extra 34 hp was obviously welcome, but it was the extra 60 ft-lbs down low that really made this LJMS cam a success. By increasing the low-speed torque production (actually through the entire curve), the LJMS cam would certainly offer increased boost response on the street (or strip). The artificial load from the engine dyno negates some of the gain, but boost response with the turbo cam would be greatly enhanced with an extra 60 ft-lbs on tap.

 

 

Test 4: NA vs BTR Stage IV Blower Cam on an SC LSX

Building a performance LS engine means using the right tool for the right job. This applies to more than just a torque wrench or feeler gauges; it applies to running the proper cam grind for the intended use and application. In this case, the application was a supercharged B15 LSX engine. Built by General Motors to withstand 15 psi (the 15 in B15), the forced-induction combo (not just blowers) featured a forged crank and pistons (powdered metal rods) along with six-bolt LSX LS3 heads.

Add a boost-friendly static compression ratio of 9.0:1 and you have the makings of the perfect combination for a supercharged cam test. All I did was add a Whipple supercharger, 150-pound injectors, and a Holley HP management system and I was ready to roll.

This test was designed to compare an NA cam to a dedicated blower grind on a supercharged LS3 application. In addition to being designed for a positive-displacement blower application, the Stage IV cam from BTR was also slightly more aggressive. The NA cam (from Comp Cams) spec’d out with a .617/.624-inch lift split, 231/247-degree duration split, and 113-degree LSA. By comparison, the BTR blower cam offered the same lift split, an extra 8 degrees of intake duration, 11 degrees of exhaust duration, and 6 degrees of LSA (113 vs 119).

Equipped with the NA cam, the Whipple Supercharged LSX produced 855 hp at 6,700 rpm and 713 ft-lbs of torque. After installation of the BTR Stage IV cam, the peak numbers jumped to 880 hp and 714 ft-lbs. The milder NA cam actually offered more power up to 4,800 rpm, but the BTR cam pulled away thereafter. Interestingly, the boost was higher with the BTR cam than with the NA cam, despite no change in pulley size.

 

 

 

NA vs BTR Stage IV Blower Cam on an SC LSX (Horsepower)

NA Cam: 855 hp @ 6,700 rpm BTR Blower Cam: 880 hp @ 6,700 rpm Largest Gain: 29 hp @ 6,500 rpm

Although designed for an NA (rectangular-port) application, the Comp cam offered plenty of power on the supercharged LSX. The tighter LSA and shorter duration on the NA cam offered more power down low on the supercharged applications, but the wilder Stage IV BTR cam came on strong at the top of the rev range.

 

 

NA vs BTR Stage IV Blower Cam on an SC LSX (Torque)

NA Cam: 713 ft-lbs @ 4,600 rpm BTR Blower Cam: 714 ft-lbs @ 5,300 rpm Largest Gain: 23 ft-lbs @ 3,600 rpm

The torque curve shows what might be considered typical of a sizable change in cam duration. Stepping up 8 degrees in cam duration and increasing the LSA by 6 degrees (from 113 to 119) enhanced top-end power production. There was a trade-off in torque production below 4,700 rpm because the milder (NA) cam offered better power down low.

 

 

Test 5: Effect of LSA on a Supercharged LSX

Does the LSA affect the boost and power curves of a supercharged LS3? Obviously the answer is yes or this would be one very short test. Typically blower cams (such as the factory LSA and LS9 cams) are ground with very wide LSAs. Those factory cams featured 121.5-degree LSAs, but it is not uncommon for blower cams to be in the 119- to 120-degree area. In comparison, typical performance cams for LS3 applications are slightly tighter, in the 112- to 114-degree range.

 

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This begs two questions: What happens if you just run your blower engine with a cam that you know works well on an NA LS3? Will a powerful LS3 cam work well once you add a supercharger?

To answer these questions, I set up a test on the GM B15 LSX engine. Equipped with a Whipple supercharger, I wanted to test two cams with distinctly different LSAs. The two cams (one from Comp and the other from BTR) were as close as possible in specs other than the LSA. The tight LSA cam from Comp had a .617/.624-inch lift split, 231/247-degree duration split, and 113-degree LSA. The BTR blower cam had a .617/.596-inch lift split, 231/248-degree duration split, and wider, 120-degree LSA.

Equipped with the 113-degree cam, the blower engine produced 758 hp and 681 ft-lbs of torque. Replacing the 113-degree cam with the BTR cam increased the power output slightly to 768 hp and 679 ft-lbs of torque. The blower cam offered slightly more power at the top of the rev range, but the tighter LSA cam offered more low-speed torque.

 

 

 

Effect of LSA on a Supercharged LSX (Horsepower)

113-Degree LSA Cam: 758 hp @ 6,200 rpm 120-Degree LSA Cam: 768 hp @ 6,200 rpm Largest Gain: 10 hp @ 6,200 rpm

The wider LSA (typical of a positive displacement blower cam) improved power production above 5,400 rpm but offered a slight bump at 5,000 rpm as well. Down low, the wide LSA lost power to the tighter LSA, but low-speed power is usually not a problem with the immediate boost response offered by a positive displacement supercharger.

 

 

Effect of LSA on a Supercharged LSX (Torque)

113-Degree LSA Cam: 681 ft-lbs @ 4,200 rpm 120-Degree LSA Cam: 683 ft-lbs @ 4,300 rpm Largest Gain: 19 ft-lbs @ 3,200 rpm

The 113-degree LSA cam increased torque very low in the rev range. From 3,200 to 3,900 rpm, the narrow LSA offered more low-speed torque, but lost out in terms of peak power to the wide LSA. The question now is, Where do you want your extra power?

 

 

Test 6: Effect of LSA on a Stroker LS3

To find out how LSA affects the power curve on NA engines, I had Crane grind me a pair of cams with identical lift and duration values but altered LSAs. Both cams featured .624-inch lift (intake and exhaust) and 232/242-degree duration splits, but one cam featured a tight 108-degree LSA, while the other came in at 120 degrees. This obviously altered the cam timing events, but the test on LSA is interesting nonetheless.

The 402 stroker test engine was actually a hybrid of sorts, featuring an LS2 block and LS3 heads. The aluminum block was treated to a 4.0-inch stroker crank from Speedmaster, along with Carrillo rods and CP (flat-top) pistons. Topping off the hybrid stroker was a set of CNC-ported Chevy Performance L92 heads. Offering a tad more than 350 cfm, the heads flowed more than enough to support the intended power level for the test. The stroker also featured a FAST LSXR LS3 intake, Big Mouth throttle body, and 17 ⁄8-inch Kooks headers.

The idea was to run the pair of cams to illustrate the power differences (if any) offered by the change in LSA. Equipped with the 120-degree cam, the stroker produced 570 hp at 6,200 rpm and 535 ft-lbs of torque at 5,200 rpm. After swapping to the 108-degree cam, the peak numbers stood at 572 hp at 6,300 rpm and 543 ft-lbs of torque at 5,100 rpm. A difference in 2 hp is not significant, but the real change came elsewhere in the curve.

The tighter LSA dramatically increased power production lower in the rev range. The cam swap netted an additional 36 ft-lbs of torque down low, but the additional torque gains continued through the rev range. Only for a short 150-rpm stint did the two cams produce the same power. The one downside to the tight (108-degree) LSA cam was idle quality because the idle vacuum was down significantly compared to the 120-degree cam.

 

 

 

Effect of LSA on a Stroker LS3 (Horsepower)

120-Degree LSA Cam: 570 hp @ 6,200 rpm 108-Degree LSA Cam: 572 hp @ 6,300 rpm Largest Gain: 10 hp @ 6,500 rpm

In terms of horsepower production, the tight 108-degree LSA cam offered more power everywhere. The 120-degree cam was able to equal the 108-degree cam for 200 rpm (from 6,000 to 6,200), but lost out everywhere else. I expected the 120-degree cam to come on strong at the top of the rev range, but on this stroker, the 108-degree was the better choice.

 

 

Effect of LSA on a Stroker LS3 (Torque)

120-Degree LSA Cam: 535 ft-lbs @ 5,200 rpm 108-Degree LSA Cam: 543 ft-lbs @ 5,100 rpm Largest Gain: 36 ft-lbs @ 3,700 rpm

It is obvious from the torque curves that the tighter 108-degree LSA cam offered considerably more torque down low and through most of the curve. I saw this same scenario on the test with the supercharged application, although I did not try a 108-degree LSA on that engine. The downside to the tight LSA cam was idle quality, but if you are after power, the 108 was definitely the way to go.

 

 

Test 7: Carb vs EFI Cam on a 417 LS3 Stroker

This test was interesting in that it came about after hearing a heated discussion online about the merits of cams designed specifically for carbureted LS applications. In truth, the carbureted cam design has less to do with what supplies the fuel than does the intake manifold design. Carbureted cams are generally designed for short-runner, single-plane manifolds rather than a specific carburetor. That enthusiasts even use the terms “carbureted” and “EFI cams” is reason enough to schedule a test.

As this and other tests revealed, the optimum cam for a given application works well with both forms of induction. By this I mean that if a cam offers more power in carbureted form, it will do so if you switch over to fuel injection.

The test engine for this comparison was a 417 stroker built from an LS3 aluminum block. Included were a 4.0-inch Scat crank, K1 6.125-inch rods, and JE forged pistons (with Total Seal rings). Topping the stroker was a set of GM Performance CNC L92 heads from Gandrud Chevrolet. The carbureted combination was run with an Edelbrock Victor Jr. intake and Holley 950 Ultra XP carburetor; the EFI combo included a FAST LSXR intake, Big Mouth throttle body, and 75-pound injectors.

In the carbureted corner was a Comp grind that offered a .623/.596-inch lift split, 247/258-degree duration split, and 110-degree LSA. The EFI cam was slightly milder with a .620/.596-inch lift split, 239/250-degree duration split, and wider 113-degree LSA. The graphs reveal that when tested with both the carbureted and EFI induction systems, the “carb” cam consistently offered more power. Neither the carb nor the EFI favored one of the cams; the carb cam was right for the application regardless of the induction system.

 

 

 

Carb vs EFI Cam on a 417 LS3 Stroker (Horsepower)

Carb Cam (carb combo): 628 hp @ 6,700 rpm EFI Cam (carb combo): 611 hp @ 6,700 rpm Largest Gain: 17 hp @ 6,700 rpm

In this comparison, I tested a pair of cams designed for carbureted and EFI applications. The carb cam was slightly wilder in specs and offered a tighter LSA. Run on a carbureted stroker, the carb cam offered more power above 5,300 rpm and below 4,700 rpm, but the two combinations yielded near identical torque values. Given the longer duration, I expected the carb cam to trade power down low to the EFI cam, but such was not the case.

 

 

Carb vs EFI Cam on a 417 LS3 Stroker (Torque)

Carb Cam (EFI combo): 604 hp @ 6,400 rpm EFI Cam (EFI combo): 585 hp @ 6,400 rpm Largest Gain: 20 hp @ 6,500 rpm

I tested the carb versus EFI cam once again on the same stroker combination, but this time it was equipped with a long-runner, EFI manifold. Once again, the carb cam offered more power above 5,300 rpm. The two produced identical low-speed power (which surprised me), but the EFI cam offered slightly more power from 4,500 to 4,900 rpm.

 

 

Written by Richard Holdener and republished with permission of CarTech Inc

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