The LS3 engine is a small block engine that was used in the Corvette C6, GTO, and Camaro while the LS7 is a small block engine that was used in the Z06 and ZR1 Corvettes. Both of these engines are very similar, but they have some differences.
The main difference between the two engines is that one is more powerful than the other. The LS7 was built for performance and will provide you with more horsepower than its counterpart, but it’s also a bit more expensive and less efficient on gas.
In this post, we’ll be looking at these two to see what significant differences they have, and hopefully help you make an easy decision on which one to go for based on your needs.
Displacement/Size
The LS3 engine has a displacement measuring 6162cc or 376.0 cubic inches, while the LS7 engines contain a 7008 cc or 427.6 cubic inch displacement.
It’s meant to fit the Corvette Z06 and Camaro Z28. The LS3 contains a 103.25 mm cylinder bore size, while the LS7 is measured at 104.8 mm.
The LS3 engine has an 8-cylinder design with a 90-degree crankshaft angle and 4 valves per cylinder, with two valves per cylinder on each camshaft (via pushrods) and four camshafts that are timed together by gears in the front of each head/block assembly (via powertrain).
Power/Torque Output
The LS3 will pump out 426 to 436 horsepower at 5900 RPM, while the LS7 is rated at 505 horsepower at 6300 RPM. The LS3 also offers a wider torque curve with a peak of 415 lb-ft of torque in its 5500 to 6000 rpm range.
Compression Ratio
The compression ratio is the amount of air that can be squeezed into a cylinder during its compression stroke. A higher compression ratio means more potential power, but it also increases the likelihood of engine knock or detonation.
The LS3 has a 10.7:1 compression ratio (10.7:1), while the LS7 mill is capable of 11.0:1 (11/100ths). This means that you’ll get better performance from your LS3 motor if you want to keep your car running at high rpm levels without knocking or detonating on you.
Fuel System
The LS7 engine requires premium fuel, featuring a 91 or higher octane level. While this is also recommended for the LS3 engine, you don’t have to use premium fuel for your car to run perfectly well.
As long as your car’s manufacturer recommends a certain type of gas and you follow those guidelines (i.e., don’t mix different grades or types), then everything should be fine.
Reliability
Reliability is a huge factor when it comes to determining the best engine. The LS7 offers a slight advantage because of its performance level, but you may end up paying more in terms of maintenance costs if your car is equipped with this engine.
The LS3 seems to come with more issues than other engines, so if you’re looking for something reliable and affordable, this might not be the right choice for you.
Cost
Like many other things in this world, the cost of an LS engine depends on what you’re willing to pay. The LS3 is relatively affordable and can be purchased for under $2,000. The LS7 costs about twice as much, but it’s still not a tremendously expensive engine.
For those who are looking for the best bang for their buck, we recommend going with the LS3. It has all the power of a high-performance engine without breaking your bank account—and it’ll still leave you with enough cash left over to buy some nice performance parts.
LS7 vs LS3 Heads
| LS7 Heads | LS3 Heads |
| Delivers 505 horsepower | Delivers 495 horsepower |
| 470 Ib-ft of torque | 473 Ib-ft of torque |
| Costs around $300 – $400 | Costs around $1,200 |
Similarities Between LS3 and LS7 Engines
Both the LS3 and LS7 are V8 engines that were designed to be used in a Corvette. Both engines have similar displacement, making them great for racing.
Also, the LS3 and LS7 have similar specs. They both produce about 435 horsepower at 6000 RPM and 400 lb-ft of torque at 4600 RPM.
Here are other similarities:
1. Block Material
The LS3 and LS7 blocks are both made out of aluminum, which is the lightest material commonly used in car engines. Aluminum is also much cheaper to work with compared to iron and steel.
While you could use a block made from either material for your next engine build, we would recommend sticking with an aluminum block for its lighter weight and lower cost.
2. Engine Type
The LS7 engines are very similar to the LS3 engines except for their bore length along with a few minor updates. These include a change in piston design, adding a water pump, and other small changes.
3. Weight
LS3 and LS7 both have similar weights. Both are made of lightweight aluminum which is a material that does not add much weight to the engine, so they are almost identical to each other. Their only difference in weight is due to different materials of connecting rods and a few other parts that can be made from steel or aluminum.
4. Lifters
Lifters are cylindrical components that are placed between the camshaft and the inlet-outlet valves. They serve two main purposes: to apply pressure on the valve and to act as a “floating” pivot point for the push/pull mechanism of each valve lifter.
The lifters used in the LS3 and LS7 are the same, so one can be used in place of another (though it’s recommended not to swap them during an engine swap).
LS3 vs. LS7 Engines – Which Is Better?
Buying an LS3 engine is a great way to get into the Corvette world, but it’s not going to give you the most horsepower. If you want more power, there are two options: upgrading to an LS7 or buying a brand-new Corvette with the latest LT1 engine.
The LC9S offers up to 514 horsepower and 460 lb-ft of torque from its supercharged 6.2-liter V8. The car can hit 60 mph in 3 seconds flat and has a top speed of 190 mph (or higher if you choose the Z06). With supercar performance at fractional supercar prices, it’s easy to understand why so many people love this car.
Read: Car Shakes in Reverse
Conclusion
The LS3 and LS7 are two of the most popular engines in the world. They both have their pros and cons, but they’re both equally good at what they do. It comes down to personal preference when it comes to deciding which engine has more value for you.
The main difference can be seen in their performance capabilities. Other differences also include; Displacement/Size, fuel system, reliability, cost, power output, and compression ratio.
Although these two engines’ differences are glaring, there are still some similarities between them. For instance, the two engines are made from the same block material which is aluminum.
Also, the weight, engine type, and lifter are similar. This means that your preference will decide the best one for you.