Comparison of LS1 and LT1 Engines


If the LT1 caused a stir when it was introduced in 1992, then 1997's LS1 was a tidal wave. Both of these engines were evolutions of Chevrolet's seminal small block V8 engine that originally debuted in 1955, and both offer performance that is a far cry from those old pavement pounders. Nearly two decades after the first LT1s hit the street, debate still rages over which one is best.


  • The LT1 was more of a stop-gap update to the old small block than a completely new engine. The LT1 sported a number of enhancements over its predecessor, including a reverse-flow cooling system and an intake system and cylinder heads designed from the outset for multi-point fuel injection. Development began on the LS1 practically from the moment the first LT1s saw daylight. The LS1 was a completely clean-sheet design and shared very few components with its predecessor.

Engine Block

  • The LT1's iron engine block is all but interchangeable with the original small block; a few small changes ensure that not everything crosses over, but most internal parts do. The LT1 has all the same strengths and weaknesses as its predecessor, but the aluminum LS1 block is in an entirely different league in terms of strength and technology. The LS1 engine block uses race-derived, six-bolt cross-bolted main caps to keep the crankshaft under heavy stress, an enhancement that makes it nearly as strong as any production iron block ever made.


  • The LT1's cooling system was reverse-flow, meaning that it cools the cylinder heads before anything else. This little trick keeps the heads cooler, allowing higher compression ratios and more power production before detonation in the cylinder. The LS1 came with a faster and more powerful computer, so its fuel injection system is much quicker to respond to changes. The LS series also came with coil-on-plug ignition, which is far more powerful and accurate than the spark-plugs-and-coil arrangement used by the LT1.


  • LS1s have a 35 to 40 horsepower advantage over their equivalent older siblings, but that power comes at a cost. LS1 engines make their power much higher in the RPM band than LT1s, so they tend to have less low RPM torque. LT1s generally offer ferocious acceleration off the line but tend to run out of breath higher in the RPM band. LS1s have a little more trouble shredding tires but work quite well in the upper RPM band (making them better suited for passing in third through fifth gears).


  • LT1s have at least as much potential as any traditional small block, which is to say about 400 horsepower with a good flowing intake, heads, headers and computer retune. Outer limits for a no-holds-barred LT1 block are quite high; over 900 horsepower is achievable with a new rotating assembly and quality race heads. Limits for a stock LS1 block are about the same, but the crank and rods are much stronger; over 600 turbocharged horsepower is possible without ever removing the valve covers.

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