Proform Parts Carburetor Metering Block Conversion Kit

Upgrade Your Holley Carb with Proform Parts Metering Block Conversion Kits

If you're serious about dialing in your fuel curve, swapping out a restrictive factory metering plate for a proper billet metering block is one of the most impactful—and often overlooked—carburetor upgrades you can make. Proform Parts brings that same commitment to performance engineering to their line of Carburetor Metering Block Conversion Kits, offering enthusiasts a straightforward path from a fixed metering plate to a fully tunable, jet-changeable block.

What Makes a Metering Block Conversion Worth It?

Many popular Holley carburetors—particularly the 4160 and 4175 vacuum secondary models—leave the factory with a simple metering plate on the secondary side rather than a true metering block. While this keeps costs down, it eliminates the ability to swap jets and fine-tune fuel delivery for your specific engine combination. A metering block conversion fundamentally changes that equation, giving tuners the same flexibility on the secondary side that they already enjoy on the primary.

Proform's Billet Aluminum Approach

Proform's conversion kits are built from high-quality billet aluminum with a black anodized finish, combining durability with clean underhood aesthetics. The kits are engineered to replace the original secondary metering plate with a purpose-built billet metering block, and each kit ships with all the hardware needed to complete the swap cleanly.

Proform offers application-specific fitments to cover the most common Holley configurations:

• Single-Inlet Vacuum Secondary Carbs (4160/4175): Part #67164C is designed for single-inlet setups. It replaces the original metering plate and includes a longer fuel bowl screw, a longer transfer tube, and all necessary gaskets and seals.
• Dual-Inlet Vacuum Secondary Carbs: Part #67163C addresses dual-inlet configurations, replacing the metering plate with a billet block and including all conversion gaskets. Note that this application requires a longer dual-feed fuel line.
• Double Pumper 4150 Carbs (750–850 CFM): Part #67165C is a full upgrade conversion for Holley 4150-style double pumper carburetors. The kit includes both primary and secondary billet blocks. The primary block retains original vacuum provisions, while the secondary block omits the power valve provision to suit the latest generation of carburetors. Both blocks also feature a four-corner idle system provision for advanced tuning capability.

Proform Parts: A Track Record in Carburetor Performance

Proform Parts has spent over 40 years building a reputation as a trusted name in the high-performance automotive aftermarket, with a catalog that spans carburetors, HEI distributors, engine tools, and more. Their metering block kits reflect that same philosophy: race-ready engineering made accessible to the weekend builder and serious racer alike. Whether you're building a dedicated strip car or refining a street/strip combo, Proform's conversion kits give you the tuning flexibility that a fixed metering plate simply can't offer.