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- What is a good rec-port cam worth on an LY6 6.0L?
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.
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- As supplied by GM (actually a local LKQ Pic a Part), the 2008 LY6 featured Variable Valve Timing (VVT), LS3-style rec-port heads and drive-by-wire throttle body.
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- To test on the dyno, we first wanted to eliminate the VVT cam and mechanism, so off came the factory coil packs.
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- Followed by the valve covers to allow access to the rockers.
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- The rockers and pushrods were then removed. Note that the rec-port heads utilized off-set intake rockers.
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.
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- The cam swap required removal of the factory damper to allow access to the retaining bolts for the front cover.
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- Removal of the cover provided access to the VVT cam and mechanism.
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- A single bolt secured the timing gear. With the bolt removed, we had access to the cam retaining plate and factory VVT cam.
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- To start our cam test, we replaced the VVT cam with a factory LQ4/LQ9 cam. This cam shared the specs with the VVT cam minus the ability to advance and retard while in operation. The VVT mechanism retarded the cam slightly at WOT to improve power production on the stock LY6.
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- Use of the stock LQ4 cam require replacing the VVT timing gear with a standard 3-bolt, 4X cam gear from an LS2 application (pt#2686481-ours cam from Gandrud Chevrolet).
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- The VVT front cover was replaced by this unit from GM (Gandrud Chevrolet) offered in a block completion kit. The front cover was supplied with the cam sensor, bolts, gaskets and retaining hardware.
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- Run on the dyno with the stock LQ4 cam, long-tube headers and a FAST 92-mm throttle body to replace the factory DBW unit, the LY6 produced 443 hp at 5,400 rpm and 467 lb-ft of torque at 4,500 rpm.
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- After the baseline test with the stock LQ4 cam, we decided to try this 54-469-11 grind from COMP Cams. The 469 cam offered a .617/.624 lift split, a 231/243-degree duration split and 113 lsa.
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?”
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- To provide the necessary spring pressure and coil-bind clearance, the factory LY6 valve springs (identical to the LS3) were replaced by these 26918 springs from COMP Cams.
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- We used this dual valve spring compressor to install the new 26918 springs.
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- Once the springs were installed, the LY6 aluminum heads were ready for the .600+ lift 469 cam.
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- We replaced the factory LQ4 cam with the COMP 469 grind.
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- After installation of the COMP cam and valve springs, the power output of the LY6 increased by just over 100 hp, to a peak of 544 hp at 6,600 rpm. The peak torque was up as well, from 467 lb-ft to 492 lb-ft, but at a slightly higher 5,200 rpm.
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.