Holley Engine Block Drill Jig

Holley Engine Block Drill Jig: Precision Tooling for the LS7 Wet Sump Conversion

Converting a dry sump LS7 engine block to a wet sump oiling system is one of the more nuanced challenges in the LS swap world — and getting it wrong isn't an option. Holley Performance addresses this with their purpose-engineered Engine Block Drill Jig, a specialist tool designed specifically for builders tackling the LS7 dry-to-wet sump transition.

Understanding the Problem This Tool Solves

LS dry sump engines have the dipstick located in the remote oil tank, meaning the boss in the block typically used for the dipstick is not drilled. When converting to a wet sump setup, that boss must be drilled. The challenge? This boss is parallel to nothing else on the block, and you only get one shot at the hole. A misaligned bore means a ruined block — an expensive and frustrating outcome on a high-performance engine build.

How Holley's Drill Jig Works

Holley developed this guide to help precisely locate the drill bit during the drilling process. Using two nearby threaded block holes, the guide creates easy alignment for a hand drill to exactly replicate the hole GM would have drilled for a wet sump application. The result is factory-correct positioning every time, without the guesswork.

The jig itself is built to a high standard of durability and usability. Key features include a drill chip evacuation port, machined billet steel construction, and a one-piece design — and it's made in the USA. This easy-to-use guide helps locate the drill bit during the process, and the innovative drill chip slot for vacuuming during drilling makes this specialty tool a great addition to any engine builder's toolbox. The jig is designed to accept a 3/8 in. drill bit , making it compatible with common shop tooling.

Why Holley Is the Right Source for This Tool

The GM LS engine has quickly become the high-performance standard in the performance aftermarket, and Holley has partnered with Hooker to offer some of the most versatile and complete LS swap solutions on the market. The Engine Block Drill Jig (part number 302-31) is a direct extension of that ecosystem — a precision accessory developed in-house by the same engineers who design Holley's LS swap oil pans, accessory drives, and EFI systems. When Holley builds a drill jig, it's engineered to work seamlessly with the rest of their LS conversion hardware.

This tool is made in the USA , reflecting Holley's commitment to quality manufacturing for performance-critical applications. For any builder taking on an LS7 dry-to-wet sump conversion, this jig eliminates the risk of a costly misdrilled block and ensures the final result matches OEM specifications — a small investment with significant consequences if skipped.

• Application: LS7 dry sump block — wet sump dipstick hole drilling
• Construction: Machined billet steel, one-piece design
• Key Feature: Drill chip evacuation slot for vacuuming during drilling
• Alignment Method: Indexes off two existing threaded block holes
• Drill Bit Size: 3/8 in.
• Origin: Made in the USA