When it comes to popular LS combinations, adding a set of rectangular port LS3 heads to your 6.0L is tough to beat. You get the strength of an iron block with a 4.000-inch bore size that will accept the high-flow LS3 cylinder heads (the LS7 head is not recommended since it was designed around a 4.125-inch bore, among other considerations). Given that the LS3 heads flow almost 70 cfm better than the cathedral-port heads that originally graced the 6.0L, we start to understand the popularity. The potential problem with assembling this 6.0L hybrid is that you need to source both a 6.0L short-block and LS3 components that include not only the heads but also the rockers, pushrods, and a dedicated rectangular port intake manifold. This works OK if you already have at least one of the major building blocks, but there is another way. The gang over at BluePrint Engines (BPE) offers just such a hybrid long-block that combines the strength and displacement of the 6.0L with free-flowing LS3 heads. Enter the BPE GM 364LS.
To demonstrate the potential of this LS combination, we took BPE up on their offer to not only run their combination on the dyno, but use it as a basis for producing additional power. To start with, BPE supplied the GM 364LS as a long-block, meaning it lacked a few important components required to make it run. The BPE 364LS featured a number of desirable features, including the iron block, forged pistons, and a static compression ratio of 9.8:1. The factory GM crank was configured with a 24X crank trigger while the block was equipped with a rear cam sensor. Topping the 6.0L short-block was a set of BPE’s own rectangular port LS3-based aluminum heads (PN PS8015). The heads were configured with 259cc intake ports, 102cc exhaust ports, and 72cc combustion chambers. Helping flow was a set of 2.165-inch intake valves and 1.600-inch exhaust valves set at 12-degree valve angles. Working with the heads was a single-pattern performance cam that featured 0.556-inch lift, 223-degrees of duration, and 114-degree LSA. The final touches were an adjustable timing chain and oil pump.
During development of the combination, BPE noted that this long-block produced 470+ hp and 455+ lb-ft of torque using the factory GM LS3 intake and 90mm throttle body. We planned to start our “going long” adventure by equipping the BPE long-block with a carbureted induction system that included a dual-plane Holley intake and 950-cfm Ultra XP carburetor. In addition to the induction system, we also installed a louvered windage tray system from Improved Racing and a GM C6 oil pan. Though BPE performed this operation, we made sure to remove and prime the oil pump prior to start-up. It was also necessary to install new front, rear, and valley covers, as well as a new factory damper. The long-block included rockers, stands, and pushrods along with a suitable valvespring package, but we added a set of factory valve covers and coil packs during testing (we didn’t want to scratch the fancy Holley Dominator covers). In order to run the normally injected LS with a carburetor, we installed an MSD ignition controller that allowed us to dial in the timing curve to maximize power production.
Since we were dealing with a new engine, we took the liberty of filling the crankcase with Lucas break-in oil, though the hydraulic roller was not nearly as sensitive as a typical flat tappet cam. After multiple computer-controlled break-in cycles, we replaced the break-in oil with Lucas 5W-30 synthetic. After dialing in the total timing (31 degrees) with the MSD controller and a single jet change on the 950-cfm Ultra XP Holley carburetor we were rewarded with peak numbers of 494 hp at 6,200 rpm and 457 lb-ft of torque at 4,400 rpm. I guess the BPE estimates on the engine were a touch conservative, but we knew there was even more to be had from this 6.0L combo. Thinking that the LS3 head would respond well to a dual-pattern cam designed for the application, we installed a Comp 277LRR grind that offered a 0.614/0.624-inch lift split, a 227/243-degree duration split, and 113-degree LSA. The BPE 6.0L responded very well to the Comp cam, with peak numbers of 522 hp at 6,500 rpm and 463 lb-ft of torque at 4,200 rpm. The cam swap offered more power everywhere, meaning it was a good choice for the BPE crate engine.
What’s next for the BPE 6.0L? Look for fuel-injection, blow-through boost from a ProCharger, and maybe even some nitrous oxide. This long-block rocks!
Two things are obvious from the dyno results, the first being the 6.0L offered impressive power in carbureted trim. Run with a Holley dual-plane intake, 950 Ultra XP carb, and MSD ignition controller, the LS3-headed 6.0L produced 494 hp and 457 lb-ft of torque. According to BPE’s website, this engine is rated at 470+ hp and 455+ lb-ft of torque. They were obviously being conservative, but we stepped things up with a cam swap. After installation of the Comp 277LRR cam, the peak numbers jumped to 522 hp at 6,500 rpm and 463 lb-ft at 4,200 rpm. Not only did the cam swap improve the peaks, but it offered power gains through the entire rev range—always a sign of good cam selection.
01. Displacing 6.0 liters, the LS3-based long-block from BluePrint Engines (BPE) featured plenty of performance potential. The orange paint gave it some LSX appeal.
02. The BPE 364LS 6.0L included a factory GM crank and rods combined with forged pistons and a 24X (gen III) crank sensor.
03. Because the long-block was supplied sans oil pan we needed to add one so we installed a C6 Corvette pan we had along with this slick windage tray system from Improved Racing. The tray, which incorporates a windage tray and trap door system, greatly improves the oil control of the GM pan.
04. The long-block was equipped with an oil pump and new timing chain. We made sure to remove and prime the oil pump prior to start-up. On the dyno we ran off the rear cam sensor but the engine came with a single-pulse sprocket so we could have read cam timing off the front with the correct cover and sensor.
05. The BPE 364LS was equipped with a single-pattern cam that offered 0.556-inch lift, 223-degrees of duration, and a 114-degree LSA. The long-block also featured a 1X, adjustable cam sprocket equipped with a Torrington bearing. We thought it odd that the engine came with a single-pattern cam given that it was running LS3-style heads. But, in the interest of science we decided to run it as it came out of the crate.
06. Feeding the 6.0L short-block was a set of BPE rectangular port LS3-based cylinder heads (PN PS8015). The heads featured 259cc intake ports, 102cc exhaust ports and 72cc combustion chambers.
07. The heads also featured a 2.165/1.600 valve package, 12-degree valve angles, and a dual-spring package designed for up to 0.650-inch lift. The long-block was supplied with (offset intake) rockers, rocker stands, and pushrods.
08. We decided to run the BPE 364LS in carbureted trim with the installation of a dual-plane LS3-based intake from Holley. A single-plane intake would make more power up top but the dual-plane is typical of what most “street” guys would run.
09. The Holley intake featured O-ring sealing to eliminate troublesome vacuum leaks. This sure beats RTV sealant everywhere.
10. The dual-plane intake was topped off with (what else?) a Holley 950-cfm Ultra XP carburetor.
11. Here is the 364LS ready for action sporting the front cover, damper, and sexy Dominator valve covers. To keep the covers in good shape we removed them during testing.
12. Running the normally injected LS with a carburetor required use of this MSD ignition controller. This unit allowed us to dial in the timing curve to maximize safe power.
13. Exhaust chores were handled by a set of 1 7/8-inch Hooker LS headers with collector extensions.
14. Run on the dyno in carbureted trim, the BPE 364LS produced 494 hp at 6,200 rpm and 457 lb-ft of torque at 4,400 rpm. The engine was plenty impressive, but we felt a dual-pattern cam might be a better match for the rectangular port LS3-based heads.
15. Out came the BPE-supplied, single-pattern cam.
16. In went a Comp 277LRR grind designed specifically for a rectangular port application. The 277 cam offered a 0.614/0.624-inch lift split, a 227/243-degree duration split, and 113-degree LSA. Equipped with the new cam, the carbureted BPE 364LS produced 522 hp at 6,500 rpm and 463 lb-ft of torque at 4,200 rpm.