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ls6 stock bottom end good to how many rpm manufacturer

- Oct 16, 2022 -

ls6 stock bottom end good to how many rpm manufacturer

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ls6 stock bottom end good to how many rpm manufacturer

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ls6 stock bottom end good to how many rpm manufacturer

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ls6 stock bottom end good to how many rpm manufacturer

[Editor’s Note: This LS6 engine upgrade guide is part of a series of LS engine upgrade guides assembled by a team of LS experts at Summit Racing that we are sharing at OnAllCylinders. The LS6 is a Gen III, 5.7L aluminum-block V8 that first appeared in the 2001 Chevrolet Corvette Z06. It is dimensionally identical to the LS1 but does feature noteworthy differences to consider if you’re building an LS6 or planning to swap one into your vehicle.

The LS6 was the top performer of the Gen. 3 LS engine family and led directly to the Gen. 4 LS2 in 2005. It first appeared in the 2001 Corvette Z06 and was available in the C5Z until 2004. It also powered the Cadillac CTS-V in 2004 and 2005. It was light at 458 lbs. dressed with accessories. The LS6 became a legend in road-racing circles with the perfect balance of power and reliability.

The LS6 intake manifold flowed more air and had a unique positive crankcase ventilation (PCV) system. It is the best factory Cathedral port car intake and was a popular swap onto LS1 engines.

The LS6’s “243” casting cylinder heads flowed another 30 cfm. The airflow combined with hollow-stem intake valve and LS6 specific valve springs resulted in a redline that was 500 rpm higher than the LS1. In addition, the chambers were smaller for a healthy bump in compression ratio.

The bottom end was stronger as well. The LS6 engine blocks were sand cast and have windows in the bulkheads for better high-rpm breathing. The pistons also had a unique alloy and the rod bolts were stronger too.

These upgrades can be installed by anyone with simple hand tools. Once this is done, we recommend taking your car to the local chassis dyno tuner for a new baseline. This ensures everything is working as it should. It also makes it easier to gauge the gains from serious upgrades later.

If hood clearance isn’t an issue, tunnel rams produce big gains at 6,000+ rpm. Single-plane intakes don’t make as much torque or power as the tunnel rams. But, for engines turning 5,500+ rpm (minimum) or using nitrous, they begin to make more sense.

Fuel injectors: The standard 30-lb. injectors support about 430 whp. Upgrading to larger injectors is needed for more. Keep in mind, the latest LS3-style injectors are the shortest, LS2 injectors were in the middle, and the LS1/6 injectors are the longest. This is a good time to involve your tuner as they will want a fully characterized injector to ensure peak driveability and power.

Milling/Decking: The heads can be taken down to 60cc. This will build 11:1 compression which runs fine on pump gas. Be aware that piston-to-valve clearance will be reduced, but cams around 230° @ .050 in. can still work without flycutting.

Lightweight LS3 intake valves can be cut to fit the seats. At 77 grams, they allow the engine to pull well beyond 7,000 rpm. The factory exhaust valves are already sodium filled and are often reused.

Many supercharger kits are bolt-on and work with stock internals and pump gas. A water-methanol injection kit is recommended. Over 600 horsepower at the wheels is just a start.

Nitrous kits and the LS6 go together like peanut butter and jelly. They’re widely available, inexpensive, and easy to install. Up to 200 horsepower is common on stock internals, but a proper tune and good fuel quality are part of the equation.

The stock pistons are a known weak point. As horsepower increases, so does heat—which, in turn, causes the top piston ring to expand. With enough heat, it will close the ring gap and the ends will butt together. When they do, a broken piston ring land is the result.

Another weak point of the stock pistons is that they don’t have valve reliefs, which limits piston-to-valve clearance. All of this is remedied by a set of

The LS6 had stronger connecting rods and bolts than the pre-2001 LS1. With the exception of the late 2004 and 2005 CTS-V, they still had press-fit pins. These rods are good to 500 hp and 7,000 rpm (naturally aspirated). With boost or nitrous, 700+ hp can be achieved if rpm is limited to 6,500. At the same time, if you’re doing forged pistons,

If you’re running a power adder, the LS6 block is good for about 800 horsepower. At that point, the main caps start to walk as they are not doweled. Head and main studs help, but there are better options. A sleeved or aftermarket block and a 4.125 in. bore and 4 in. stroker crank nets 427 c.i.d. Iron blocks, sleeved aluminum 5.3L Gen. 4 blocks, and aftermarket 6 head bolt blocks are all common options. The LS6 block itself isn’t a good candidate for re-sleeving due to the windows cut into the main bulkheads.

ls6 stock bottom end good to how many rpm manufacturer

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ls6 stock bottom end good to how many rpm manufacturer

The 1997-1998 LS1 blocks had thin cylinder sleeves. Honing them 0.005 in. oversized is the safe maximum. Later blocks had thicker sleeves that can be honed 0.010 in. Upgrading to a 4 in. stroke ups the displacement to 383 c.i. or 6.3L.

Another way to increase displacement is to re-sleeve the block. Generally, the 1999-2000 LS1 block is the preferred starting point. It has solid main webbing and better rear oil galley passage. The 1997-1998 LS1 blocks have solid main webbing, but less desirable oiling.

LS6 blocks are not good candidates for re-sleeving. These blocks have windows cast into the bulkheads for better breathing. When machining for larger liners, there is less material to support the cylinder. This will result in a weaker engine block.

The excess heat can cause the top piston ring to expand. Under enough heat, it will close the ring gap and the ends will butt together. When they do, a broken ring land can result.

Another weak point of the stock pistons is that they don’t have valve reliefs. This will limit piston to valve clearance. A set of Forged Pistons should be high on your priority list.

Rods with the 2001+ bolts are good to 500 hp. and 7,000 rpm (naturally aspirated). With boost or nitrous, 700+ hp. can be achieved if rpm is limited to 6,500. Forged Connecting Rods is another popular upgrade.

The stock crankshaft can handle about 900 hp and 7,000 rpm (for a limited time). A Forged Crankshaft upgrade will add strength to the bottom end. Stroker cranks will also add extra displacement. If rods and pistons are replaced, it makes sense to upgrade the crank at the same time.

Milling/Decking: Without modifying the intake manifold, LS1 heads can be taken to 62cc chamber volume. The LS6 can be taken down to 60cc. This will create up to 11:1 compression on pump gas. However, be aware that piston-to-valve clearance will be reduced.

LS engines respond extremely well to Cam Swaps. Just match the other parts you choose to support it. This is not just Valve Springs and rockers. It includes intake, heads, exhaust, torque converter, rear-end gears, etc.

The trunnion bearings in the stock rocker arms are another known weak point. Retrofit Trunnion Kits fix this. Upgrading to Full Roller Rockers is recommended for over 0.600 in. lift.

If you have an LS1, upgrading to the LS6 intake is inexpensive and popular. The throttle body diameters are identical. Aftermarket Intakes can produce strong gains with a 90mm (LS2) throttle body.

When changing intakes, take note of the throttle body. F-body cars and the 2004 GTO were cable operated. The Corvettes came with electronic throttle control (drive-by-wire).

If hood clearance isn’t an issue, Tunnel rams produce big gains at 6,000+ rpm. Single plane intakes don’t make as much torque or power as the tunnel rams. But, for engines turning 5,500+ rpm (minimum), or subject to nitrous backfires, they begin to make more sense.

Fuel Rails: Factory rails need to be addressed around 700 hp. This will depend on how much extra fuel is being flowed in through Methanol or Nitrous nozzles.

Custom tuning will be required to properly adjust the fuel and ignition systems. Because of the popularity of LS upgrades, chassis dyno tuning with the factory ECU is most common.

ls6 stock bottom end good to how many rpm manufacturer

ANSWERBack in 1955, you (or your grandpa) might have posed a very similar question: "Why does that new-fangled small-block Chevy make more peak power and torque at a higher rpm than my trusty Flathead Ford?" The short answer: "Technology marches on." Broadly speaking, modern Gen IIIandlater LS engines benefit from nearly a half century of progress since the original small-block"s debut, many of which are thanks to the tribal knowledge gleaned by racing traditional Chevy V8s. Racers demand efficiency, but so do ever-tightening emissions and mileage standards. Some of the GM engineers who helped design various aspects of the LS engine were deeply involved in performance and racing, either in their "off" time or as the result of previous assignments to Chevrolet"s official racing programs.

To a large extent, it all begins with the cylinder heads. One can more or less predict the power potential of a given-displacement, normally aspirated engine based on its cylinder-head intake-port flow numbers. As Comp Cams" Billy Godbold puts it, "The greater the cylinder head"s inta