Three Cam Tests on an LS3 Engine - Bumpstick Boomerang

We test the differences between three custom grinds on one LS3

Richard Holdener Mar 31, 2014 0 Comment(s)
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Let's face it, the LS3 is a fantastic motor, offering an impressive combination of power, reliability and even fuel mileage. One other area where the LS3 excels is how well it responds to performance upgrades, especially camshafts. The reason why the LS3 responds so well to wilder cam timing is because it already has sufficient displacement, compression, and head flow. All that is lacking to dramatically improve the power output of any LS3 motor is cam timing. With heads and intake already capable of supporting over 600 hp, the mild stock LS3 cam is definitely the limiting factor. Given this situation, cam upgrades for the LS3 have become hot sellers. Plop just about any cam in an otherwise stock LS3 and watch the power soar. The one potential problem with this situation is how much cam is too much, and what exactly is the limiting factor when it comes time to choose a cam?

While an LS3 will certainly respond to more aggressive cam timing, there are two limitations,, inherent in the stock combination. First up, the stock valve springs were designed for the stock cam, and are insufficient for performance use, especially given the current crop of .600+lift cams. The cure is to swap the stock springs for one of the many spring kits available. Given that Brian Tooley Racing (aka The Spring King) was behind the testing that generated this data, we installed a set of their double springs, seats, and titanium retainers. This allowed us to properly test the merits of the cams without fear of valve float or coil bind. Though impressive power gains are commonplace with cam swaps, we decided to illustrate not just the power, but also the idle vacuum, and piston-to-valve clearance. It is this clearance that is ultimately the limiting factor, in terms of how wild you can go with a cam-only upgrade on your LS3. Unfortunately for enthusiasts, cam duration (lift plays less of a part) and piston-to-valve (P-V) clearance are inversely related. Each successive step up in duration decreases P-V, until it becomes non-existent. The important question for LS3 owners is, how much is too much?

Gm Ls3 Crate 2/14

The GM LS3 crate motor from Gandrud Chevrolet had been used for a variety of tests, but was put back in stock configuration for this cam comparison.

To illustrate just how far you can go, we decided to compare three different cam profiles, supplied by Brian Tooley Racing, against the factory LS3. The three cam profiles increased duration in successive steps. In addition to the power gains on the otherwise stock LS3 crate motor, supplied by Gandrud Chevrolet, we also monitored the idle vacuum, cranking compression, and measured the all-important piston to valve clearance.

After swapping the valvesprings, the LS3 crate motor was configured on the dyno with a set of long-tube headers, a complete Aeromotive fuel system, and tuned to perfection with the Holley Performance HP EFI system. Not surprisingly, the stock cam offered plenty of idle vacuum (over 20 inches) and acceptable peak power numbers. The baseline pulls produced peak numbers of 496 hp at 5,800 rpm, and 491 lb-ft of torque at 4,700 rpm. The measure piston-to-valve clearance exceeded .150, meaning, it was more than adequate for performance use. Engine builders recommend having .100 in-Hg P-V to ensure there is no contact when things start to move. Check out the results of the three cams, and know that we ran one of them with only .003 P-V, but would never recommend doing so on any application.

Ls3 Valve 3/14

1 The first thing to go was the stock LS3 valve springs. They were inadequate in terms of pressure and coil bind for our high-lift cam testing.

Brian Tooley Racing Ls3 Valve Spring 4/14

2 Brian Tooley Racing came to the rescue with a new valve spring upgrade for the LS3. The kit included the double valvesprings (good for .650 lift), titanium retainers, locks, spring locaters, and seals.

Install Valve 5/14

3 Installed on the stock LS3 heads, the Brian Tooley spring upgrade allowed us to rev the motor safely past 6,500 rpm, even with the 235 cam approaching .650 lift.

Install Long Tube 6/14

4 The stock exhaust manifolds were replaced with a set of long-tube headers, feeding dyno mufflers.

Hp Efi 7/14

5 Tuning is a critical factor when testing, and we relied on the Holley HP EFI system to optimize not only power production, but idle quality as well.

Install 3 Bolt Cam 8/14

6 The stock LS3 cam featured a single-bolt cam, but all of the test cams featured the early 3-bolt design. We simply installed the appropriate 3-bolt (4x) cam sprocket.

Cam Swap Dyno 9/14

7 Cam swaps on the dyno were a snap, and each successive increase in intake duration resulted in more power, but less piston-to-valve clearance.

Ls3 Dyno 10/14

8 Using just a cam, we managed to increase the power output of the LS3 from 496 hp to 573 hp, while torque was up from 491 lb-ft to 526 lb-ft. Before you rush out to buy a big cam, know that the 235-degree cam offered just .003 piston-to-valve clearance, and would almost certainly destroy your motor when the valves inevitably came in contact with the piston tops. A much safer bet would be the 231 cam that produced 566 hp with a still tight .041 P-V.


Cam 1: Stock LS3
Lift: .551 in/ .525 ex
Duration @ .050: 204 in/211 ex
LSA: 117
Idle vacuum: 20.3 in-Hg
PV Intake: .150+
PV Ex: .150+
Cranking Compression: 205 psi
Peak Power: 496 hp @ 5,800 rpm
Peak Torque: 491 lb-ft @ 4,700 rpm
Ave HP (3,000-6,500): 408.9 hp
Ave TQ (3,000-6,500): 452.4 lb-ft
Tq @ 4,000 RPM: 461 lb-ft

Dyno Graph Cam Test Stock Ls3 11/14

The stock camshaft offered a perfect idle, good power, and plenty of P-V. Now it was time to step things up with the other cams.


Cam 2: 224 Cam
Lift: .624 in/ .590 ex
Duration @ .050: 224 in/232 ex
LSA: 113
Idle vacuum: 20.3 in-Hg
PV Intake: .117
PV Ex: .150
Cranking Compression: 205 psi
Peak Power: 547 hp @ 6,300 rpm
Peak Torque: 514 lb-ft @ 5,100 rpm
Ave HP (3,000-6,500): 37.6 hp
Ave TQ (3,000-6,500): 82.6 lb-ft
Tq @ 4,000 RPM: 480 lb-ft

Dyno Graph Cam Test Ls3 Vs 224 Cam 12/14

The 224 cam demonstrated just how much the LS3 motor was in need of wilder cam timing. Stepping up 20 degrees of duration (@.050) resulted in a gain of just over 50 hp, upping the peak power output from 496 hp and 491 lb-ft to 547 hp and 514 lb-ft of torque. The extra duration had little effect on the idle vacuum, though, the Holley EFI did allow us infinite tuning to maximize idle vacuum. The extra duration made itself known in decreased P-V, down to a still acceptable .117 on the intake, and right at .150 on the exhaust. The cranking compression matched the stock cam with 200 psi. Note from the graph that the cam upgrade improved power production through the entire rev range.


Cam 3: 231 Cam
Lift: .617 in/ .624 ex
Duration @ .050: 231 in/239 ex
LSA: 113
Idle vacuum: 17.1 in-Hg
PV Intake: .041
PV Ex: .098
Cranking compression: 200 psi
Peak Power: 566 hp @ 6,400 rpm
Peak Torque: 517 lb-ft @ 5,200 rpm
Ave HP (3,000-6,500): 441.4 hp
Ave TQ (3,000-6,500): 485.4 lb-ft
Tq @ 4,000 RPM: 477 lb-ft

Dyno Graph Cam Test 224 Vs 231 13/14

Compared to the 224 cam, the 231 cam offered additional power (566 hp vs 547 hp), and a few extra lb-ft (517 vs 514 lb-ft), but things started getting serious close in terms of P-V clearance. The intake valve was now only .041 in-Hg away from the top of the piston. While we have run cams with this little P-V, miss a shift or put the thing into valve float, and they may just have a coming together. Such contact will spell disaster for one or both of them, and possibly the entire motor. Note that we saw a slight drop in power down low with the wilder cam timing. The trade off in power is often associated with increased intake duration. The wilder 231 cam dropped idle vacuum down to 17.1 inches, and cranking compression was down slightly to 200 psi.


Cam 4: 235 Cam
Lift: .647in/.612ex
Duration @ .050: 235 in/244 ex
LSA: 111 degrees
Idle vacuum: 13.7 in-Hg
PV Intake: .003
PV Ex: .075
Peak Power: 573 hp @ 6,400 rpm
Peak Torque: 526 lb-ft @ 5,200 rpm
Ave HP (3,000-6,500): 449.4 hp
Ave TQ (3,000-6,500): 494.5 lb-ft
Tq @ 4,000 RPM: 484 lb-ft

Dyno Graph Cam Test 231 Vs 235 14/14

Unlike the previous test, the 235 cam increased the power output through the entire rev range, compared to the 231 cam. The peak numbers jumped from 566 hp and 517 lb-ft with the 231 cam to 573 hp and 526 lb-ft of torque. Credit optimized opening and closing points and a tighter lsa for the power gains, but just take a look at the non existent P-V. Though we took a (very big) chance on running this cam, this minimal clearance would certainly lead to destruction on the street or strip. Single-digit P-V is simply unacceptable. The power gains also cost idle quality, as the 235 cam dropped idle vacuum down to 13.7 inches, though, cranking compression dropped to just 195 psi. If you didn't mind the drop in idle quality, this cam would be the hot ticket with replacement pistons that featured valve reliefs. For now, cams with 235 degrees of duration (and minimal P-V) would be best left on the shelf until after the rebuild.

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