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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 lift curves for the LS3 camshaft.    Drawing: GMPT Communications. Click Image For Larger View.

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)

year RPO

 

int.

lift

int. dur

at .004

int. dur.

at .050

int. open

at .004

in. close

at .004

in. open

at .050

in. close

at .050

int.

CL

int.

area

int. area

increase

MY01 LS6

 

13.34 mm

.525 in

270°

204°

BTDC

81°

ABDC

18

ATDC

42

ABDC

118°

ATDC

1862.9

mm/deg.

n/a

MY02 LS6

 

14.01 mm

.551 in

267°

204°

BTDC

80°

ABDC

19°

ATDC

43

ABDC

120°

ATDC

1936.9

mm/deg.

4%

MY05 LS2

 

13.34 mm

.525 in

270°

204°

BTDC

81°

ABDC

18°

ATDC

42

ABDC

118°

ATDC

1862.9

mm/deg.

0

MY06 LS7

15.06 mm

.593 in

276°

210°

BTDC

88°

ABDC

18°

ATDC

48°

ABDC

122°

ATDC

2166.4 mm/deg.

16%

MY10 LS3

 

14.01 mm

.551 in

267°

204°

BTDC

80°

ABDC

19°

ATDC

43

ABDC

120°

ATDC

1936.9

mm/deg.

4%

 

Camshaft Profile, Exhaust Comparison

(All lift figures are valve lift)

year RPO

 

exh.

lift

exh. dur.

at. .004

exh. dur.

.050

ex. open

.004

ex. close

.004

ex. open

.050

ex. close

.050

exh.

CL

exh.

area

ex. area

change

MY01 LS6

 

13.33 mm

.525 in

275°

211°

65°

BBDC

30°

ATDC

37

BBDC

6

BTDC

114°

BTDC

1914.6

mm/deg.

n/a

MY02 LS6

 

13.91 mm

.547 in

282°

218°

69°

BBDC

33°

ATDC

42

BBDC

4

BTDC

115°

BTDC

2046.6

mm/deg.

8%

MY05 LS2

 

13.33 mm

.525 in

275°

211°

65°

BBDC

30°

ATDC

37

BBDC

6

BTDC

114°

BTDC

1914.6

mm/deg.

0

MY06 LS7

14.95 mm

.589 in

296°

230°

81°

BBDC

35°

ATDC

53

BBDC

3

BTDC

119°

BTDC

2359.4 mm/deg.

23%

MY10 LS3

 

13.33 mm

.525 in

275°

211°

66°

BBDC

29°

ATDC

38

BBDC

7

BTDC

115°

BTDC

1914.6

mm/deg.

0

 

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."

The LS3 intake valve (right) compared to the LS6 unit. The new part has a larger, polished head and a hollow stem. Image: Steve Constable/GMPT Communications.

 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.

Bird's eye view of the L92/LS3 rocker arm assembly. The offset intake rocker is obvious. What is not be so obvious is the more robust rocker cover seal surface. Image: CHpg Staff.

The LS3 intake rocker's offset is nearly a quarter of an inch. The material remains investment-cast steel. The rockers are typical of O.E.s in that they have roller trunnions but not roller tips. Roller tips are really not necessary and are used in aftermarket aluminum rockers because its cheaper and easier to add a roller rather than some other method of hardening the valve tip. Image: CHpg Staff.

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.

The LS3 intake returns to lost core manufacturing. This is the bare intake. It is assembled with injectors and fuel rails by its supplier before being shipped to a GM engine plant. Image: Steve Constable/GMPT Communications.

"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.  

The guts of an industrial-strength iPod? Hardly. This is the circuit board of the Camaro's E38 engine controller. Image: CHpg Staff.

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

Displacement      376 cubic inches
Bore  4.064-in. 
Stroke 3.622-in.
Compression Ratio  10.7:1
Cam duration@.050 lift 204°/211° 
Valve Lift  .551/.525
Power 422 hp@5900 rpm
Torque 408-lbs/ft@4500 rpm
Rev Limit  6600 rpm
Weight 448 lbs.

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.

We love the "exploded photos" of engine parts that GM Powertrain has been putting out every so often. This one is the Camaro SS's, manual trans. LS3. Steve Constable/GMPT Communications. Click Image For Larger View