ApplianPar 1" Open-Center Carburetor Spacer Adapter — Square-Bore 4-Barrel Fit, Includes Gaskets & Studs

ApplianPar 1" Open Center carburetor spacer adapter installs between the intake and a square-bore 4-barrel carb to increase plenum volume and improve throttle response without blocking cross-bore signals.

This single-inch open-center spacer is engineered to fit popular square-bore carburetors — including Holley 4150/4160, Carter AFB and many Edelbrock 4BBL models — and ships with gaskets and mounting hardware for a straightforward installation. Its open-center design maintains cross-over airflow and avoids the flow restriction of a tapered or annular spacer, while adding thermal isolation and extra plenum space. The package includes one spacer, two gaskets and four studs with nuts so you have everything needed for bolting it between the carb and intake manifold.

How does this spacer affect engine breathing and throttle feel?

The 1.0-inch thickness increases the plenum volume directly beneath the carburetor, which can smooth airflow pulses and give a more immediate throttle response. Because this spacer is open center, it does not block cross-bore passages, preserving consistent fuel distribution across cylinders.

• One-inch rise for added plenum capacity and pulse tuning
• Open center keeps cross-bore and signal passages clear
• Improves throttle transition without shaving off top-end flow

Will it fit my carburetor and what comes in the box?

This adapter is made for square-bore, four-barrel carburetors including Holley 4150/4160, Carter AFB and many Edelbrock 4BBL bases. The kit arrives ready to install with the spacer, two pre-cut gaskets and four mounting studs and nuts to secure the carburetor to the intake manifold.

• Compatible with Holley 4150 and 4160 bolt patterns and Carter AFB bases
• Includes 1 spacer, 2 gaskets, 4 mounting studs and 4 nuts
• Designed for square-bore 4-barrel carburetor base patterns

Is the open-center style better for my setup than a tapered or annular spacer?

Open-center spacers prioritize unimpeded airflow through the carburetor bore and maintain cross-bore functionality, making them a good choice for balanced distribution and drivability. Tapered or annular spacers can add velocity or top-end gains in some builds but may alter fuel signals; choose open center when you want a straightforward increase in plenum volume and thermal isolation.

• Open center preserves fuel/air signal passages for even cylinder distribution
• Less likely to require carb re-jetting than restrictive spacer types
• Good compromise between drivability and modest performance tuning

How easy is installation and are there any fitment tips?

Installation is simple for anyone familiar with carburetor removal and reinstallation: lift the carb, position the spacer with supplied gaskets, install the studs and torque the nuts to factory specs. Use gasket sealant if desired and double-check throttle linkage and vacuum line clearances after assembly.

• Lift carburetor, place gasket, then spacer, then second gasket if needed
• Hand-start studs and torque nuts evenly to manufacturer torque values
• Verify throttle linkage travel and vacuum hose routing before final tightening

Who is this for: ApplianPar's 1" open-center carburetor spacer serves street rods, muscle cars, classic V8 restorations and DIY engine tuners who run square-bore 4-barrel carbs and want a simple, reversible upgrade to plenum volume and throttle response. It’s ideal for owners seeking improved drivability and thermal separation without aggressive port shaping or complex re-jetting. If you use Holley 4150/4160, Carter AFB, or many Edelbrock 4BBL carburetors and want a bolt-on spacer with included hardware, this kit is a practical choice.