Words and Photos: Richard Holdener
We have seen it happen again and again, but no matter how many times you see the impressive power gains offered by a cam swap on an LS application, it never gets old. The go-to LS for most enthusiasts remains the venerable 5.3L. Used in millions of GM truck applications, the workhorses are available in droves at local wrecking yards. Blessed with adequate displacement, compression and head flow, the 5.3L responds very well to upgrades, including cam swaps. What you have in the factory LS, is a motor that possesses everything else it needs besides adequate cam timing. The combination of sufficient displacement, adequate head flow and a good intake manifold mean all that is missing is a good cam. As good as these little 5.3L motors are, wouldn’t a 6.0L be even better? The answer to this question is yes, but a 6.0L (any 6.0L) commands a premium priced tag. The question then isn’t so much whether a bigger motor makes more power (it does), but whether the extra power is worth the price. That is a question only the buyer can decide, but let’s take a look at what happens when you do step up to the bigger motor.
The 6.0L is available in a number of different varieties, ranging from (of all things) an iron-headed LQ4, to an all-aluminum L76 variant that featured not only rectangular-port aluminum heads, but Variable Valve Timing (VVT) and Active Fuel Management (AFM-basically displacement on demand). The most prevalent seem to be the LQ4, but these only came equipped with iron heads in 1999-2000. The slightly higher compression LQ9 versions (with flat-top pistons) offered a tad more power, but things started to get serious for truck owners once GM introduced the rectangular-port heads on the 6.0L. To put things into perspective, the switch from the already-good, cathedral-port 317 used on the LQ4 and LQ9 motors to the 823 heads on the LY6 and L76 variants, resulted in an increase in airflow of 65-70 cfm per runner! That is a huge jump in potential power, with no other change. That these later motors also featured higher compression (than the LQ4) and VVT showed that truck engineers were certainly listening to the needs of truck owners.
The question for us was, with the advent of these rec-port headed 6.0Ls becoming available, how well do they respond to a cam upgrade for they guys looking to swap one into a street rod, muscle car or even a truck application? To find out, we snatched one up from a local LKQ Pick Your Part and got it right up on the dyno. Because we would be running it with an aftermarket FAST ECU, we decided to eliminate the VVT cam and assembly that came factory equipped on this 2008 LY6 combination. That’s right, even before we could start our cam test, we had to perform a cam swap. Out came the VVT cam and mechanism (see photos) and in went a standard 6.0L LQ4/LQ9 cam profile. According to our research, this cam profile offered identical specs to the VVT version, minus the ability to advance and retard the cam timing. Run at WOT, the VVT would retard the cam timing slightly to improve power, but we figured the vast majority of engine-swap applications would opt for the locked cam anyway. Run on the dyno with the LQ4 cam (specs-.467/.479 lift, 193/201 duration, 116 lsa) the LY6 produced 443 hp at 5,400 rpm and 467 lb-ft of torque at 4,500 rpm.
After establishing the baseline, we decided to swap in one of our favorite rec-port cam grinds offered by COMP Cams. The 54-469-11 cam offered a .617/.624 lift split, a 231/247-degree duration split and 113-degree lsa. This cam was getting near the limit of available piston-to-valve clearance with the factory piston and large valve used on the rec-port heads. Designed with extra exhaust duration to offset the flow differential between the high-flow intake and standard LS exhaust ports, the cam has always proven powerful (even on cathedral-port applications). In addition to the 469 cam, we also installed a set of 26918 beehive valve springs. The spring upgrade was necessary to provide adequate spring pressure and coil-bind clearance for the .600+ lift cam. Swapping the springs was made simple with the use of a dual-spring compressor. Once installed and tuned with the FAST XFI management system, the newly cammed LY6 produced 544 hp at 6,600 rpm and 492 lb-ft of torque at 5,200 rpm. Measured peak to peak, the 469 cam improved the power output by over 100 hp. The gains were even greater higher in the rev range, as the factory LQ4 cam fell off rapidly at higher engine speeds. By now it should be obvious, the question isn’t why should you perform a cam upgrade on your LS, the question now is, “Why you even need to ask why?”
6.0L LY6-LQ4 vs COMP 469 Cam
To test the power output of the VVT-equipped 6.0L LY6, we first replaced the VVT cam with a standard LQ4 grind. Other than the ability to advance and retard the cam, the specs were said to be identical. Equipped with the fixed stock cam, headers and FAST 92-mm throttle body, the otherwise stock LY6 produced 443 hp at 5,400 rpm and 467 lb-ft of torque at 4,500 rpm. After installation of the COMP54-469-11 cam, the power output jumped to 544 hp at 6,600 rpm and 492 lb-ft of torque at 5,200 rpm. The COMP cam and valve spring upgrade was worth an easy 100 horsepower on this rec-port 6.0L.