Our In-Depth Look the Camaro SS's LS3 Page 4

Cam and Valvetrain

The LS3 camshaft is typical Gen 3/4 faire--a gun drilled steel billet with roller hydraulic lifters. It's based on the one used in the LS6 which was used in a few 2002 Camaro SSes. Its intake lobe comes from the '02 LS6 cam. The exhaust profile is from the 385-horse Corvette LS6 of 2001. For LS3, in order to reduce overlap, lobe separation was increased a degree. The net sum of all this was more intake airflow and a smoother idle.

The mix of lobe profiles, also, means there are two different base circles, 19-mm for the intake and 19.3-mm for the exhaust. Because of the different base circles, to keep valve train geometry optimized, two different valve lengths are used in the LS3 with intakes 0.6-mm. longer than exhausts.

Camshaft Profile, Intake Comparison

(All lift figures are valve lift)

Camshaft Profile, Exhaust Comparison

(All lift figures are valve lift)

We interviewed valvetrain DRE, Jim Hicks several times in recent years for stories on LS1, 2 and 6 and he told us, "All our cams (prior to LS6) had the same base circle radius. We had a problem, if we wanted higher lifts: the nose of the cam would approach the same diameter as the cam bearing journals or even exceed them.

"Obviously, that means you can’t install the cam in the engine–little bit of a problem. Your only alternatives are to increase rocker arm ratio, which we weren’t going to do (for this engine), or reduce the base circle radius."

The first base circle reduction, for the ’01 LS6, did not require a change in any other valvetrain part, however, the 405-horse cam for '02 was a different story as was the LS3's intake lobe, which uses the same profile.

"I wasn’t comfortable reducing base circle that much," Hicks told the CHpg, "without compensating for it somehow, because the position of the plunger within the hydraulic lifter is not optimal any more–you’re too high in the lifter.

"There are different ways to correct the geometry. The one we selected to minimize the impact on our manufacturing operations was to increase the length of the valve. Both valves in the 02 LS6 and intake in the LS3 are 0.6-mm. longer than the valves in other engines."

 Taking another page from the Z06 engine book, the LS3 intake valve, because its larger diameter increases mass, now has a hollow stem to get weight back down to where the valvetrain is stable to a 6600 rpm rev. The exhaust valve is made of "21-2N, a nitrogen-strengthened, austenitic stainless steel commonly used for valves. The  LS3 valve spring is the "double-shotpeened," Gen 3/4 high-performance unit, originally developed for the LS6.

Another new feature of the LS3 valve gear is offset intake rocker arms. Similar in concept to those used for the LS7, they have a 1.7:1 ratio. The offset is .246-in. and exists so the pushrod could be moved sideways about a quarter of an inch, allowing those wider intake ports.

Intake and Exhaust

The Camaro intake manifold has been changed. One reason is the intake port  is wider and its floor is higher in the head. That, alone, drove development of a new intake. LS1s all used a glass-reinforced Nylon-6,6 intake manufactured using the lost core process. In 2005, for the first Gen 4, the LS2, GM switched to a different material, Nylon-6, and went to a vibration-weld manufacturing process.

"Since the ports moved up and their shape changed," John Rydzewski stated, "we needed a new intake. It's still made of Nylon-6 but it's now done with the lost core process. The new manifold is specific to all passenger car applications that use this cylinder head.

"A vibration-welded intake has different shells. One port can be a combination of an upper portion and a bottom portion with the runners welded together on the side. It's a pretty good seam, but there might be a little crosstalk (port-to-port leakage) which can rob you of some power. We had seen that in some applications, so we went (back) to a lost-core intake.

The new intake was also reshaped for better flow. Yoon Lee, who went on to lead the project that developed the LS9 supercharger assembly, did the development. The intake manifold has a smoother path, right down to the head. Compared to '01-'02 LS1, restriction decreased by 2-3% at 13.5mm valve lift.

There's some extra structure–a different type of webbing on the bottom of the manifold–to stiffen it up. This new intake has metallic compression limiters inside the manifold bolt bosses vs. the previous all-composite compression limiters. With the tall, unsupported bosses, over time, if you over-tighten, you can get what Small-Block engineers call "creep." The term is a bit of a misnomer because it implies that the manifold, as a unit, moves. Better terms might be "extrude" or "deform". Over time and especially if the bolts are over-tightened, the Nylon may extrude, radially, away from where the fastener load is applied. The metal inserts in the bolt bosses prevent that.

LS3's injectors come from LS7. With 100 more horsepower than the last Camaro V8, LS7's 5-gram/sec. injectors were necessary. The 90-mm. throttle body was originally developed for the 2005 Vette's LS2 and works very well in the 2010 Camaro application.

The exhaust manifolds are similar to the units introduced on the LS2 but have a slight change in each exhaust runner where it bolts to the head to match the LS3's revised exhaust port exits.

These manifolds were revolutionary in '05, as GM employed a new material, cast iron with higher silicon and molybdenum content, which made a stronger casting. As a result, the wall thickness of the part could be reduced by about 25% and reduced engine weight by 10.5 lbs. A new MLS exhaust gasket was, also, released.

Engine Controls and Bin 4 Emissions

The engine control module (ECM) or "controller" as the guys who develop this stuff say, was new for 2006 and will be used on the 2010 Camaro LS3. Known internally as "E38", this new controller is part of GMPT's "Strategic Engine Management Complexity Reduction Initiative"–yeah, GM is like the Federal Government when it comes to thinking-up names. This program will result in only three engine management systems which share as many parts as possible.

The E38 has enhanced electronic throttle control (ETC) ability and it supports the 58x crankshaft position signals and 4x camshaft position signals which have become more common. It is a more thermally-robust design which can be mounted under the hood and close to the engine which reduces wiring harness length and complexity. It also uses connectors which meet standards set by the Electrical Wiring Component Applications Partnership (EWCAP) of the United States Council for Automotive Research (USCAR), a organization set-up by GM, Ford and Chrysler to foster the technology base of the domestic automotive industry.  

As for the deep-geek aspects of the E38: its CPU is Motorola's PowerPC. It's a 32-bit, RISC processor running at 40Mhz with 64Kb or RAM and 2 Mb of flash ROM.  The RAM nonvolatile and ignition independent and the flash EPROM, which contains the E38's calibration is nonvolatile and battery independent. 

One capability enabled by the combination of the E38, LS3's improved combustion dynamics and enhanced emissions control devices, is compliance with the more stringent, "Tier 2, Bin 4" exhaust emissions standard. These "bins" get tougher in a downward progression so, Bin 4 is cleaner than Bin 5. "With Bin4 emissions," John Rydzewski told us, "useful life hydrocarbon emissions are reduced by over 12% and useful life NOx emissions are reduced by over 40% compared to the LS2." The LS2 is the last engine for which we have emissions numbers to compare. We can state confidently that the LS3's emissions are way less than that of the final LS1s and LS6es in 2002 Camaros. We should add that, Bin 4 emissions compliance comes with 100 more horsepower and better fuel economy than we had in '02.

More performance, more green, less gas, weighing about 15-lbs less than an LS1? Works for us!

Looks like the LS3 Team at GM Powertrain did a damn fine job on the Camaro SS's new engine.

LS3 at a glance

The Camaro Homepage would like to thank Ron Meegan, John Rydzewski, Lou Oniga, Jim Hicks, Tom Read and Susan Garavaglia of GM Powertrain and Al Oppenheiser, Chief Engineer, GM Global Rear Wheel Drive Team, for their assistance with this article.