626HP LS3 Stroker Build - Supersize Me

Who Needs a Power Adder? By Stroking an LS3 to 416 ci, Wringing out 622 hp is Cake

Stephen Kim Jun 5, 2014 0 Comment(s)
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Billet Double Roller Timing Set 2/23

7. To endure the rigors of high-RPM and the increased valvespring pressure of the 416, LME opts for a JP Performance billet double-roller timing set. It has multiple keyways cutouts on the crank gear for up to 8 degrees of cam advance or retard.

Degree Wheel Camshaft 3/23

8. Using a degree wheel, LME verified the installed centerline of the camshaft. It was advanced two degrees to help bulk up low-end torque.

Grinding Timing Cover 4/23

9. Since a stock LS3 utilizes a single-roller timing set, fitting an aftermarket double roller set requires grinding the back of the timing cover for clearance. LME made quick work of this process on its CNC machine.

Outlet Grind 5/23

10. The stock LS3 oil system is already plenty stout, but the LME 416 ramps up the oil flow even more with a Melling high-volume pump. Before installing it, LME radiused the outlet and grinded down all the sharp edges to improve flow.

Cylinder Heads Ls1 6/23

11. All the cubic inches in the world don’t mean squat without a set of high-flow cylinder heads, and the factory LS3 castings are among the greatest production small-block heads ever built. GM engineers improved upon the already potent cathedral-port LS1 heads by pushing the pushrod passages over to the side, freeing up space for a larger rectangular port with a raised entrance.

Pac Dual Valvesprings 7/23

12. To maintain valve control at high RPM, LME fitted the heads with PAC dual valvesprings that feature 170 pounds of seat pressure and 430 pounds of open pressure. They’re anchored in place by lightweight titanium retainers to keep valvetrain mass and valve float to a minimum.

Intake Ports 8/23

13. After a trip through LME’s proprietary CNC program, the factory LS3 cylinder heads flow 365 cfm through the intake ports at 0.630-inch lift. That puts them right on par with the stock LS7 heads at a fraction of the cost.

Cnc Porting 9/23

14. The CNC porting bumps the exhaust port flow up to 235 cfm. Although the LS3 head castings have been criticized for having poor exhaust flow relative to the intake ports, 235 cfm is still right on par with a big-port Gen I small-block Chevy head. Likewise, using a slightly longer exhaust duration on the camshaft addresses the situation nicely.

Ls3 Ported Heads 10/23

15. LME’s ported LS3 heads retain the factory 2.165-inch hollow-stem intake valve and 1.600-inch stainless steel exhaust valves. They received a three-angle cut, and LME blended them into the stock 70cc combustion chambers.

Trick Flow Pushrods 11/23

16. Sending the lobe lift to the rocker arms are GM LS7 hydraulic roller lifters and 7.400-inch Trick Flow pushrods. The GM hydraulic lifters perform more like solid roller lifters, and can maintain valvetrain stability past 7,000 rpm.

Gm Head Gaskets 12/23

17. In order to tighten up the quench clearance as much as possible, LME sets the pistons to 0.010-inch “out of the hole” and utilizes 0.048-inch-thick GM head gaskets. This yields a 0.038-inch quench clearance. Tighter quench not only produces more horsepower, it also reduces the potential for detonation by improving the homogenization of the air/fuel mixture.

Head Bolts 13/23

18. Although head studs offer the ultimate in clamping force, head bolts are more than adequate for a naturally aspirated combination like the LME 416. The ARP bolts were torqued down to 70 lb-ft.

Comp Cams Trunnion Conversion Kit 14/23

19. The LME 416 uses the stock LS3 rocker arms, but with a twist. To enhance longevity under increased valvespring pressure and higher RPM, LME fortified the stock rockers with a Comp Cams trunnion conversion kit. The trick setup replaces the stock pivots with heavy-duty rocker arm trunnions and bearings. At $135, the conversion is a heck of a lot cheaper than a set of aftermarket rocker arms.

Fast Lsxr Manifold 15/23

20. Since the cylinder heads can only flow as much as an intake manifold will allow, LME matched up its ported LS3 castings with a high-flow Fast LSXR manifold. It features a 102mm inlet, which was matched to a Nick Williams billet throttle body of the same diameter.

Torque Power Graph 16/23
Ls3 Cylinder Superflow Dyno 17/23

21. A testament to the efficiency of the LS3 cylinder heads, the 416 required just 28 degrees of ignition advance on LME’s Superflow dyno. With the air/fuel ratio dialed in at 11.8:1, the motor kicked out 622 hp at 6,200 rpm and 574 lb-ft at 5,250 rpm.


Serious Airflow

Big engines make big torque and improve drivability by taming the adverse affects of a long-duration camshaft. However, they can’t take advantage of their greater power potential unless airflow into the cylinders is increased accordingly. As such, LME has developed a proprietary CNC porting program that dramatically improves the airflow of the factory LS3 cylinder head castings. From the factory, the stock LS3 heads flow roughly 320 cfm of air at 0.600-inch lift through the intake ports along with incredible low- and mid-lift flow numbers. LME’s CNC ports improve upon those already impressive figures by moving 365 cfm at peak lift. Flow wise, that puts the LME LS3 heads firmly into the territory of the vaunted LS7 head castings.

Dyno Time

The enormous airflow LME’s LS3 heads can achieve is more than enough to support well over 700 hp if matched with a big, nasty solid-roller camshaft. However, that would require spinning some serious RPM, and placing undue stress on the short-block and valvetrain. Instead, experienced builders like LME resist the urge to go big in a street/strip application in the name of civility. By matching the cylinder heads up with a mild 235/250-at-0.050 hydraulic roller cam, the LME 416 produces a stout 622 hp at a very reasonable 6,200 rpm on the company’s Superflow engine dyno. Furthermore, with 574 lb-ft of torque on tap, putting around town in traffic or at low RPM is a pleasant, cam-surge-free affair. So while mega horsepower combos are great for single-purpose racing engines and bragging rights, well-rounded combos like LME’s 600-Plus LS3 excel equally both on the street and at the track.

Stroker L99?

Although the LME 416 is built to LS3 specifications, that doesn’t mean automatic-equipped L99 fifth-gens can’t get in on the action, too. Typically, converting an L99 over to LS3 specs involves replacing the stock L99 lifters, lifter buckets, pushrods, timing set, timing cover, and lifter valley cover with standard LS3 hardware. Fortunately, all those components are already included in the LME 416’s build sheet, so there are no additional components that need to be converted over with LS3 hardware. Just drop the LME 416 LS3 in and hit the gas.

Sources

Late Model Engines
Houston, TX 77041
713-849-4505
http://www.latemodelengines.com

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