LS7 Engine Upgrade Guide: Expert Advice for LS7 Mods to Maximize Performance

[Editor’s Note: This LS7 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 the LS7 Engine

The LS7 is a Gen. IV, 7.0L, aluminum small block engine. It was available in General Motors’ high performance cars between 2006 and 2015. The 427 c.i.d. LS7 is the largest displacement engine in the LS family. It was the most powerful naturally-aspirated GM production V8 engine since the 1960s and was based on the C5-R Le Mans Corvette racing engine.

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[Every engine spec you’ll need can be found here: LS7 Engine Specs: Performance, Bore & Stroke, Cylinder Heads, Cam Specs & More.]

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How to Get More Power From Your LS7

The LS7 makes over 500 horsepower naturally aspirated right out of the box. As good as it is, racers and the aftermarket love this engine and tons of great parts are available. Each level will provide more performance than the one before it. The only question is…How far do you want to go?

Basic Bolt-On Upgrades for LS7

These upgrades are relatively easy on your back and your wallet. They will improve the performance and fuel economy of a stock engine. These are upgrades that can often be installed in your garage with simple hand tools:

• A cold air intake
• A set of headers
• An aftermarket exhaust
• A cooler thermostat

Once the bolt-ons are done, there’s a good chance the factory ECM is far from optimized. With the LS7, the owners usually have a long list of upgrades planned so it’s good to get a baseline. We recommended you call your local chassis dyno tuner and find out what programmer they prefer. In most cases, they can tweak more power out of your car than a canned tune. It establishes a good upgrade path and you’ll know what to expect as things get more serious.

Top-End Upgrades for LS7

Building the top-end is the next level of upgrading the LS7 engine. Top-end upgrades include the cylinder heads, camshaft, valvetrain, intake manifold, and throttle body. These upgrades are great for a naturally aspirated engine on pump gas.

All LS engines respond well to a cam swap. The LS7 is no exception. Going up to 0.660 in. of valve lift is common on the LS7. The other specification to consider is duration.

The table below gives some information on what to expect from different cams.

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Upgrading the camshaft will require matching valve springs. While you’re at it, the trunnion bearings in the stock rocker arms are a known weak point. We strongly recommend a trunnion upgrade kit.

The LS7 intake manifold left a lot of power on the table compared to GM’s later manifolds. An aftermarket intake manifold is the answer. Regardless of the manifold, you will want at least a 102mm throttle body. Going Speed Density is another option to remove the MAF restriction and pick up a bit more power. The following table will give you an idea of what you can expect for power with a medium-sized cam.

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If the intake is off, it’s also a good time to add a 4-corner steam kit. This will add coolant flow to keep hot spots from occurring. The dreaded #7 piston cracking is the result of hot spots, as the top ring can’t dissipate heat into the coolant. The top ring butts and the top or second ring land snaps as the ring has nowhere else to go but up.

The LS7 cylinder heads perform well for stock heads. However, the flow on the exhaust side is limited. The stock valve guides also wear quickly. One option is to replace the valves, guides, mill the heads and CNC port them. Titanium retainers are also recommended.

Aftermarket cylinder heads are a better option. They’re all new and more cost effective than replacing all the worn parts in the original heads. In many cases, the geometry has been optimized and machining accuracy is better than the originals. 400+ cfm at .700 in. lift is possible, but look at .400 in. numbers and port cross section when comparing heads.

LS7 Power Adders

A small supercharger or nitrous kit can add 175-250 hp. At that power level, a stock bottom end will live but you’ll need a good tune with adequate octane.

• A roots-style supercharger is dependable and makes great torque in the low- and mid-rpm range.
• 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.
• A nitrous oxide kit (at low settings) is great for street driving with stock internals. Up to a 200 shot is common on stock internals.

If you haven’t done the steam kit we mentioned earlier, now is a good time!

LS7 Fuel System & Tuning

All of the upgrades we have talked about so far have focused on getting more air through the engine. To make power, you also need fuel.

• The stock injectors are good to about 600 hp.
• The stock fuel pump is good to about 700 hp.

The LS7 has a fairly stout factory compression ratio. When running boost, you can use a water-methanol system to supply extra fuel and lower charge air temps.

There are many fuel system upgrades on the market. Drop-in fuel pump modules and external pumps are popular. Other options are electronic voltage controllers and hotwire kits to maintain or increase pump pressure.

Bottom End Upgrades for LS7

The LS7 block and rotating assembly are strong. Naturally aspirated and low-boost engines don’t require any upgrades. However, you will need to start making changes around 700 whp.

• The stock pistons are good up to about 750 hp.
• The stock titanium rods are good to around 850 hp.
• The block and the crankshaft will handle about 1,000 hp.

Stock pistons are cast and they will crack. Forged pistons are a smart upgrade.

If you’re doing pistons, most will go with an aftermarket forged crank and steel rods at the same time. There are a couple reasons for this.

The titanium rods are light, but they aren’t chamfered for the heavy fillets found on aftermarket cranks. Titanium is also a gummy material and care must be taken when resizing. Maintaining the plasma-sprayed surfaces on the sides of the big end is critical. Without the coating, the rods will seize against each other on the rod journal.

Because the engines are often used in track cars pulling high-Gs, oiling can be an issue. Running the larger dry-sump tank along with better windage trays and traps is the first step. From there, hybrid systems use the factory pump in conjunction with an extra scavenge pump. High-end systems replace the internal pump with an external. It has multiple scavenge sections and a pressure section to ensure constant oil supply.

Boring & Stroking an LS7 Engine

The bore diameter on a LS7 is 4.125 in. It’s recommended to not go past .005 in. oversize when honing. If you go bigger, you will want an aftermarket engine block with thicker sleeves.

You can increase the displacement of the 7.0L (427 c.i.d.) engine. Due to the complexity, we encourage you to consult an experienced engine builder. The chart below gives the specs for common bore and stroke combinations.

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(Information for this article originally appeared in this Upgrading the Gen. 4 LS7 Engine article at Summit Racing’s searchable database of FAQ tech info. Go there and search “LS engines” for a comprehensive collection of LS engine tech information.)