L77 6.0L Engine Upgrade Guide: Expert Advice for L77 Mods to Maximize Performance

[Editor’s Note: This L77 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. For a primer on the entire LS engine universe, read LS Engines 101: An Introductory Overview of the Gen III/IV LS Engine Family.]

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Intro to L77 Engines

The L77 is a newer version of the L76 with added Flex-Fuel capability.

First offered in 2011, it came in the Australia’s Holden VE2/VF, and the Chevrolet Caprice PPV (read: cop car special) through 2017.

The L77 makes 362 horsepower and it’s a workhorse. This upgrade guide is going to be a little different from most of . This is because many of these engines are still used in commuters. Performance is valued if it can be done without flushing money down the gas tank.

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[Every L77 engine spec you’ll need can be found here: L77 6.0L Engine Specs: Performance, Bore & Stroke, Cylinder Heads, Cam Specs & More.]

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How to Get More Power From Your L77 Engine (Bolt-Ons)

For many people, upgrading an L77 starts with adding a cold air intake.

The factory exhaust system is very restrictive in an effort to reduce the 4-cylinder mode drone. A set of headers and a catted X-pipe flow a lot of air, but the drone becomes obnoxious. So how do we deal with that? Easy! We can tune it out with a AFM disabler or increase performance overall with a programmer.

The factory tune was very conservative. We recommend that you talk to your local chassis dyno tuner and decide on a computer programmer.

• Tune out AFM activation.
• Correcting the fuel and ignition timing tables.
• Raising the factory redline keeps your vehicle in the meat of the powerband longer. This is important with a Caprice PPV’s 2.92 rear gears.
• Raising shift points and firmness (see above).
• Torque limiting can be completely shut off.
• Shift points can be raised.

Tech Tip: The 5^th-gen. Camaro differentials bolt right in with ratios starting at 3.25.

Getting a tune makes it easier to dial in a bigger cam and injectors later on. Before going to the tuner, we recommend installing a colder thermostat to open up the L77 tuning window.

Below are some more upgrades you can make to improve the performance of an L77 engine.

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Upgrading the L77 Camshaft and Valvetrain

If you’re doing an AFM delete kit, there will never be a better time to swap in a cam.

[Read LS Tech: How to Delete or Disable Active Fuel Management (AFM) on GM Engines for more info and part numbers.]

An LS3 cam isn’t a bad choice, but it’s only a little bigger than the L77’s factory cam.

An LS9 cam is the next step up. It’s not a bad choice and will make a lot of power at the top of the powerband, but there are better choices. What you’re looking for is power gains really starting around 3000 rpm for best average power between there and 6500 rpm.

If you’re still driving daily, cams in the 215-220 degree intake-duration range can be tuned to idle like stock and still provide good mileage.

Cams in the 220-225 range are a little more serious, but are still easy to tune and driveability is still good. If the car is turning into more of a weekend warrior, you can get into the 230-degree range without flycutting pistons.

What if you already have a power adder?

Generally, supercharger cams and nitrous cams will have slightly more lobe separation and longer exhaust duration. Turbo cams reduce overlap with less exhaust duration split in relation to the intake.

The stock rockers are good up to 175 lbs. of seat pressure and 450 lbs. open. You will want to install a trunnion kit for added reliability. Want to save some shop labor? You can buy rockers with the trunnion kits already installed. This also saves you the cost of the installation tool.

Tech Tip: When you’re pulling the cam, switch out the spring-loaded timing chain tensioner for the more-reliable wedge-style (early) LS2 damper.

Here are a few parts commonly used for an L77 cam swap: LS2 timing chain, LS7 spec lifters, LS2 timing chain damper, and thick-wall chromoly pushrods.

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L77 Power Adders

L77 engines are a popular choice for people that want to stay naturally aspirated, but if you do decide to boost, here are a couple of things to address:

• A 4-corner steam kit reduces hot spots that can cause the rings to butt and snap the piston’s ring lands.
• The 42 lb. fuel injectors will support around 525 whp which is enough for most. We’ve addressed those in the next section below on fuel system upgrades.

Okay, here’s the fun stuff:

• A nitrous oxide kit (at low settings) is great for street driving with stock internals. Up to a 200-shot is common. Keep in mind the tight piston ring gap is the limiting factor beyond that. If you’re wanting to get serious, a single-plane intake is less prone to break from a nitrous backfire. A plate system has better distribution than the original intake, but an eight-nozzle fogger system is even better. Running higher octane fuel is advised.
• Turbocharger installations for a PPV aren’t common, but have been done. There are companies producing kits for the Pontiac G8 that would be a logical starting point. Be prepared for serious fabrication.
• A Roots-style supercharger is dependable and makes great torque in the low- and mid-rpm range. It’s great for melting tires. The supercharger kits designed for the Pontiac G8 can be modified to fit. Another economical option is a take-off 1.9L blower from an LSA along with the taller lid from the ZL1. You’ll still have to run your own lines, but the Zl1 heat exchanger and pump are common and not expensive. The ZR1 pump has higher capacity and is another option. The aftermarket has many kits to help you put this part of the system together.
• A centrifugal-style supercharger is lightweight and makes more power at high rpm. This is partially due to a larger intercooler mounted in front of the radiator. They don’t have quite the curb appeal of a Roots, but make great power. Again, a supercharger designed for a Pontiac G8 can be modified to fit.

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Upgrading the L77 Fuel System and Tuning

We recommend looking at the injector’s part number before taking it to the tuner.

The L77 came with 42-lb. injectors supporting roughly 500 whp (supercharged), but closer to 600 if naturally aspirated.

The most common L77 injector upgrade is the L9H injector. It bolts in and flows close to 30 percent more fuel. Fuel injector characterization info is widely available, but you’ll still want to talk to your tuner about it before the swap.

Being Flex Fuel-capable, the single pump used in the PPV was the same as the ZL1. The module itself is different. Dual pumps from the CTS-V are another option. Keep in mind tuning the fuel pressure control module is required to match the variable pressure curve with the injector table.

Other options to maintain or increase pump pressure include electronic voltage controllers and hotwire kits. When running boost, you can use a water-methanol system to supply extra fuel and lower charge air temps.

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Upgrading the L77 Intake Manifold and Throttle Body

GM really did its homework with the factory intake. Can you improve upon it? Yes, but there are probably other areas where money is better spent.

But if you love your PPV and just hit the lottery, go with a Edelbrock cross-ram.

The low-end torque of the factory and the top-end of the tunnel ram. Dual throttle bodies to top it off.

Like the intake, the 90mm throttle body is pretty good. Unless you’re seeing increased restriction—logging less than 97 kPa at wide-open throttle (WOT) and redline—you can save money a little longer.

Ask your tuner about going with a speed density tune. Doing so will remove the MAF restriction and will give you more power.

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[Trying to find an LS or LS-based Vortec engine for a swap or build? Check out Part 1 and Part 2 of our LS Spotter’s Guide.]

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Upgrading L77 Cylinder Heads

The L77 cylinder heads are similar to the LS3 heads except they used a heavier solid stem intake valve.

• The stock heads can be CNC-ported for more airflow. Flow numbers can be as high as 373 cfm at .700 lift. Lightweight hollow-stem LS3 valves will drop right in. Between the light valves and better springs, the engines will pull cleanly to 7,000 rpm. If you’re looking to boost to 800+ hp; a heavy-duty aftermarket stainless intake valve is a bit tougher and won’t tulip as quickly from the heat. Milling the heads .030 will bump compression to 10.8:1 and will increase power everywhere. Piston-to-valve clearance will be tight with cams beyond 230 at .050 in. of intake duration.
• A better option is aftermarket heads. They reduce downtime, they’re all-new, and you can usually offset the added cost by selling your original heads. Valve angles are typically laid over to 13.5 degrees for increased piston-to-valve clearance. They flow better and the cross-sections are great for naturally aspirated or boosted engines. When comparing heads, look at the .400 in. lift numbers as a general indicator of how the heads will perform. With a medium-sized cam, 500+ whp (naturally aspirated) is a goal that is easily met.

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Upgrading the L77 Rotating Assembly

On the L77 engine, pistons are the weak link and you probably already know someone who has popped one.

A set of forged pistons is a good idea and you can increase compression while you’re at it.

They have stronger wristpins, thicker ring lands, and the added valve reliefs allow you to run big cams. If you’re going over 800 hp, a set of .200 wall tool-steel pins is a good idea.

The L77’s Gen. 4 rods are stronger than the Gen. 3 rods and have full floating pins. They can handle about 800 hp and 7,000 rpm in boosted applications (at least for a while). They are likely to bend before they break when subjected to real track conditions.

If you’re getting forged pistons, upgrade to forged connecting rods at the same time. Big 7/16-inch rod bolts will go a long way to keep things together over 7,000 rpm.

The L77 crank was cast but strong. The main reason for a stroker crank is added cubic inches. With heads and manifolds available that breathe well above 7000 rpm, more cubes can bring the power peak back into hydraulic roller territory for more power under the curve.

Performance rotating assemblies are available in many combinations.

A couple notes of caution:

• The 6.0L aluminum blocks had slightly longer cylinder sleeves than the iron blocks 5.500 in. vs. 5.430 on average). Much of the piston skirt drops out of the bottom of the cylinder at BDC. The best piston manufacturers have compensated for this by eliminating skirt taper until a point well above where it meets the bottom of the cylinder sleeve at BDC. Any skirt taper at this intersection acts as a razor blade and will wear out the piston quickly. This is especially true of the 427ci combination and the piston design is critical to long life.
• The blueprint deck height of the block is 9.240 in. It’s best to measure deck height before ordering your rotating assembly. Thicker head gaskets or using an aftermarket 6.098-6.100 in. rod will ensure enough piston-to-head clearance.

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Upgrading the L77 Engine Block

The L77 engine block has a 4.000-in. bore diameter and can be safely bored to 4.030 in.

If you’re thinking about supercharging, pistons are available starting at 4.005in. and in several steps up to 4.030 to maximize cylinder wall strength.

You can make 850 whp with a couple of simple upgrades like head studs and LS9 head gaskets. Race gas, E-85, or water-methanol injection is required.

It’s always worth it to invest in a chassis dyno tune to find fuel, spark, and other issues that are harder to spot at the track.

The factory main caps aren’t doweled. It’s better to reduce ignition timing and compensate with added boost to reduce the cylinder pressure spikes that can lift heads and cause the main caps to dance.

Main studs should be added anytime you’re this deep in the engine.