How to ID an LS Engine by VINĬhevrolet’s LS and LS-based Gen III and Gen IV small-block engines are generally known by their RPO code. If the engine you are looking at has been modified, the guide may not give you the right answer. Please note that this guide is intended for stock engines. Just answer a few basic questions and the tool will be able to tell you what LS engine you have (or at least really narrow down your options). The LS experts at Summit Racing created an interactive tool to help you easily make a positive ID by answering a few questions. If you don’t have the VIN, you can still identify the engine by visual inspection if you know what to look for. The easiest way to tell the difference is to check the 8th digit of the Vehicle Identification Number (VIN) on the original vehicle. To ensure you’re using the the right parts, you need to know which LS engine you’re starting with.
The similarities between them make several LS parts interchangeable, but there are critical differences too. There are more than 40 variations, including the LS-based Vortec truck engines.
