What is the difference between Chevy LS and LT engines?

In my shop, the most common question from restoration customers who want modern drivability under a classic hood is: LS or LT? The answer used to be simple — it is still LS for 95% of applications. Here are the actual differences so you can make an informed call for your specific build.

LS Family (Gen III/IV, 1997–2013)

The LS replaced the old small-block Chevy in 1997 and ran in various forms through 2013. Key characteristics:

• All-aluminum block (most variants) or cast iron (truck versions like the LQ4/LQ9)
• Pushrod OHV design — compact dimensions that fit easily in classic car engine bays without modifying firewalls
• Returnless fuel injection — a single fuel pump, minimal modification for classic swaps
• Enormous aftermarket: Holley, Edelbrock, Chevrolet Performance all make direct-fit intake manifolds, carb-look throttle bodies, and swap headers for virtually every classic car platform
• Available displacement: LS1 (5.7L), LS2 (6.0L), LS3 (6.2L), LS6/LS7 for performance builds

LT Family (Gen V, 2014–present)

The LT arrived with the C7 Corvette and subsequently spread through the truck lineup. Key differences from LS:

• Direct injection — requires a high-pressure fuel pump and secondary low-pressure pump; significantly more complex fuel system for swaps
• Active Fuel Management (cylinder deactivation) — can be disabled via tune but adds controller complexity
• Variable valve timing — requires electronic control that is harder to integrate in period-correct builds
• Higher power output: LT1 in C7 makes 460 hp stock; LT4 supercharged makes 650 hp

The Verdict for Classic Car Swaps

For 99% of classic car swap builds, the LS is the correct answer. The LS6 (405 hp, available as Chevrolet Performance crate engine) or the LS3 (430 hp) are the sweet spots — both have complete swap kit ecosystems from multiple suppliers and produce power levels that overwhelm most classic car chassis. The LT makes sense only for a purpose-specific high-power build where 650 hp is genuinely necessary and fuel system complexity is acceptable.