The LS7 is specially designed and built to make over 500 hp. All the stock components are matched to each other. Changing one thing can affect the performance of the other parts.
Upgrading the LS7 can be expensive and complicated. Often, when you change one part, you will need to change other parts at the same time. If you don’t do it right, you will get less power and performance.
There are a few levels of upgrades. Each level will provide more performance than the one before it. However, they will also be more involved and require deeper pockets. The question is “How far do you want to go?”
Bolt-on Upgrades
These upgrades are relatively easy on your back and your wallet. They will improve the performance and fuel economy of a stock engine.
- A Cold Air Intake
- A set of Headers
- An Aftermarket Exhaust
- A Computer Programmer
Top End Upgrades
Changing the top end parts is the next level of upgrading the engine. This includes the heads, cam, valvetrain, intake, and throttle body. These upgrades are great for a naturally aspirated engine running pump gas.
The LS7 intake manifold and throttle body work great on a stock engine. However, if you want more power, you need to feed the engine more air. The stock intake will be a restriction with a big cam and high flowing heads.
An Aftermarket Intake Manifold is the only answer.
|
Manifold Style |
Peak Horsepower |
Torque |
|
Long Runner |
+ 20 hp. |
More low-end |
|
Short Runner |
+ 35 hp. |
Less low-end |
|
Tunnel Ram |
+ 50 hp. |
Good through entire rpm range |
Regardless of the manifold, you will need at least a 102mm Throttle Body.
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.
Stock heads can be CNC ported for even better airflow. Milling the heads can increase your compression ratio. While you're at it, replace the valve guides too.
Aftermarket Cylinder Heads are another option. These heads will flow even better than ported stock heads. Different chamber sizes can also fine-tune your compression ratio.
All LS engines respond well to a Cam Swap. The LS7 is no exception. A new cam will put the increased airflow of your new heads and intake to work.
Going up to 0.660 in. of Valve Lift is common on the LS7. Any higher and the valvetrain geometry becomes a problem. The other specification to consider is Duration.
The table below gives some information on what to expect from different cams. (We are assuming a naturally aspirated engine running pump gas.)
|
Intake Duration (@ 0.050 in.) |
Horsepower Estimate (at the wheels) |
Idle Quality |
Notes |
|
210° (Stock) |
About 450 hp. |
Smooth |
N/A |
|
220° - 230° |
+ 50 hp. |
Slightly noticeable |
N/A |
|
230° - 240° |
+ 75 hp. |
Steady lope |
N/A |
|
240° - 245° |
+ 100 hp. |
Rough |
Poor driveability at low rpm |
|
245° or more |
+150 hp. |
Very rough |
Short runner intake and aftermarket heads required to match the rpm range |
Upgrading the camshaft will require the matching Valve Springs. Titanium retainers are also recommended. They will match the lightweight valves and reduce Valve Float.
The trunnion bearings in the stock rocker arms are a known weak point. We strongly recommend a Trunnion Upgrade Kit. Swapping in a set of Full Roller Rockers is another option.
Power Adders
A supercharger or nitrous kit can add 100-150 hp. on pump gas. At that power level, a stock bottom end is still acceptable.
- 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 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.
-
- Higher settings (for racing) will require an upgraded rotating assembly.
Bottom End Upgrades
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 hp.
- The stock pistons are good up to about 750 hp.
- The stock titanium rods 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.
Most people change the crank and rods between 800 – 1,000 hp. Swapping steel rods for the titanium rods will throw off the balance of the stock assembly. Aftermarket Cranks also have a large fillet radius that won’t work with stock rods. When you do upgrade, a billet center counterweighted crankshaft will flex less and extend the life of the main bearings.
Boring & Stroking
The LS7 already has thin cylinder sleeves to allow for the 4.125 in. bore diameter. You can hone the cylinders 0.005 in. oversize. If you go any bigger, you will need an Aftermarket Engine Block.
You can increase the displacement of the 7.0L (427 c.i.d.) engine. However, it is pushing the limits and we encourage you to consult with an experienced engine builder. The chart below gives the specs for common bore and stroke combinations.
|
Engine Size |
Bore Dia. |
Piston Comp. Height |
Stroke |
Rod Length |
Wristpin Dia. |
|
7.0L (427 c.i.d.) |
4.125 in. |
1.338 in. |
4.000 in. |
6.076 in. |
0.9252 in. |
|
7.2L (441 c.i.d.) |
4.125 in. |
1.050 in. |
4.125 in. |
6.125 in. |
0.927 in. |
|
7.4L (454 c.i.d.) |
4.125 in. |
0.990 in. |
4.250 in. |
6.125 in. |
0.927 in. |
Fuel System & Tuning
All of the upgrades we have talked about have focused on getting more air through the engine. To make power, you also need fuel and spark.
- The stock injectors are good to about 600 hp.
- The stock fuel pump is good to about 700 hp.
All significant changes to an engine will also require a tune. Tuning involves changing the fuel and ignition curves in the computer to optimize the engine’s performance. Hand-held tuners are simple to use. However, they have limits. Custom tuning is more complicated. But, a good tuner can get the best performance from your engine.