Carburetor Mounting Bolt

What Are Carburetor Mounting Bolts?

Carburetor mounting bolts and studs are the fasteners that secure a carburetor to the intake manifold on carbureted engines. Though they're small in size, these components play a critical role in maintaining a proper, leak-free seal between the carburetor base gasket and the manifold. A loose or improperly torqued carburetor can cause vacuum leaks, erratic idle, fuel delivery problems, and even fire hazards — making quality mounting hardware far more important than it might appear.

Bolts vs. Studs: What's the Difference?

Carburetor mounting hardware comes in two primary forms: traditional hex-head bolts and threaded studs paired with nuts. Bolts thread directly into the intake manifold and are tightened from the top of the carburetor flange. They're simple and effective, especially on cast iron manifolds. Studs, on the other hand, thread into the manifold permanently and use washers and nuts to clamp the carburetor flange down. Many builders prefer studs for aluminum manifolds, since repeatedly threading and unthreading bolts into soft aluminum can damage the manifold's threads over time. Studs also act as alignment guides, making it easier to position the carburetor and gasket accurately during installation — especially useful when working around tight throttle linkage and other obstacles.

Proper torque is also essential: carburetor fasteners typically require only modest torque — roughly 7–10 ft-lbs — so over-tightening is a common mistake that can distort the carb base or strip manifold threads. Always follow the manufacturer's recommended specification.

What to Look for When Buying Carburetor Mounting Hardware

• Thread Size: Most V8 performance carburetors use 5/16-18 (coarse) threads on the manifold side and 5/16-24 (fine) threads on the nut side. Always verify your application before ordering.
• Stud Length: If you're running a carburetor spacer, you'll need longer studs to account for the added height. Kits are available in multiple lengths to suit spacer stacks of various thicknesses.
• Material & Finish: Options range from black oxide-coated steel for a stealthy look to polished stainless steel for show engines. Stainless resists corrosion in the harsh under-hood environment, while chromoly offers excellent strength-to-weight ratios for race applications.
• Kit Contents: Look for kits that include hardened flat washers and hex nuts, which provide a more consistent clamping load than bare studs alone.

Top Brands in Carburetor Mounting Hardware

Moroso is a trusted name in performance engine hardware, and their carburetor stud kits are a favorite among enthusiasts. Their signature Bullet Nose design features studs that are rounded on one end, making it significantly easier to start the nuts during installation. Kits include four studs, hardened flat washers, and jam nuts — everything needed to mount a carb cleanly and securely.

ARP (Automotive Racing Products) is widely regarded as the gold standard in high-performance fasteners. ARP carburetor studs assist with gasket placement and feature a unique nut-starter radius that helps prevent cross-threading. Available in polished stainless steel, black oxide, and chromoly in a broad range of lengths, ARP kits cater to everything from mild street builds to all-out race engines.