We ship Mon - Fri. 12PM EST cutoff time for all orders. RETURNS NOT ACCEPTED for: wire, custom-length pigtails, harnesses, or extensions.

Holley DIY Engine Wire Harness Shop

Holley EFI is one of the top providers of aftermarket automotive parts on the planet. They offer engine management systems for GM Generation III and Gen IV LS-series engines, as well as many other popular makes. We saw an opportunity to allow you to use the stock Holley harness, and without any cutting or splicing, adapt those connections to work with your GM engine. If you want or need to, we also offer pigtails for your cutting and splicing needs. (Sometimes it's just a cleaner build with a splice instead of an adapter, we get it.)

Wire harness products are built in Erie, PA by EFI Connection, LLC!
CONNECTOR KITS, TERMINALS, AND CABLE SEALS
We offer a complete selection of genuine OE connector kits for enthusiasts who are building their own engine wire harness. What's more? We also offer replacement terminals and cable seals!

Browse our selection of Holley EFI Connector Kits
Browse our selection of Holley EFI Replacement Terminals
Browse our selection of Holley EFI Replacement Cable Seals
ADAPTER & EXTENSION HARNESSES
LS engines sometimes have sensors and fuel injectors specific to that series. We offer an impressive selection of adapter and extension harnesses to make your engines equipment plug and play. For many items we offer, you can also choose from a variety of harness lengths!

Browse our selection of Holley EFI Adapter Harnesses
Browse our selection of Holley EFI Extension Harnesses
BUILD-TO-LENGTH PIGTAIL ASSEMBLIES
Instead of cutting, crimping, and splicing with your own tools, we have a solution for you to take advantage of our production tooling to create OE quality pigtail assemblies for your Holley EFI project. Choose the wire length you need and we'll do the rest! Wire colors and AWG sizes will even match the production Holley EFI engine harness assemblies.

Browse our selection of Holley EFI Pigtail Assemblies
AUTOMOTIVE WIRE
Our selection of OE quality automotive wire is unmatched - period. Choose from all wire sizes and color combinations found in production CORE engine harnesses...even proper fusible link wire.

Browse our selection of Automotive TXL Wire
Browse our selection of Automotive Fusible Link Wire