NOS Nitrous Oxide Distribution Block

Why the Distribution Block Is the Heart of a Direct Port Nitrous System

When a nitrous system graduates from a single-nozzle plate setup to a full direct port nitrous oxide distribution block arrangement, one component becomes absolutely critical: the distribution block. Its entire job is to split a single incoming nitrous (and in wet systems, fuel) feed into perfectly equal streams — one for each cylinder. Even a slight imbalance between outlets can mean one cylinder running lean while another runs rich, with predictably destructive results. That is why the precision of the block's machining and the quality of its materials matter just as much as any other part in the system.

NOS Distribution Blocks: Precision Machined for Balanced Flow

NOS (Nitrous Oxide Systems) has been the benchmark name in nitrous since the late 1970s, when founders Mike Thermos and Dale Vaznaian commercialized nitrous injection for automotive use and set nearly every significant drag racing performance milestone with their systems. Today, as a Holley Performance brand, NOS brings that same race-proven engineering philosophy to every component in their lineup — including their distribution blocks.

Precision machining is the defining characteristic of NOS distribution blocks. NOS distribution blocks are precision machined to help distribute balanced amounts of nitrous and fuel to each intake port, ensuring consistent delivery across all cylinders. Every block uses a standardized 1/8" NPT female inlet, and the line offers a choice of 1/8" NPT or 1/16" NPT female outlets to match your line and nozzle configuration. This flexibility makes them compatible with a wide range of direct port system builds, from street/strip applications to dedicated race cars.

What's in the NOS Distribution Block Lineup

NOS offers several configurations to suit different builds and performance goals:

• Standard 1-In / 4-Out Block (16710NOS): The workhorse of the lineup. A compact, aluminum-bodied block finished in durable black anodize, with a 1/8" NPT inlet and four 1/8" NPT outlets. Ideal for 4-cylinder direct port applications or as individual cylinder feeds on larger engines paired with multiple blocks.
• 1-In / 4-Out Block with 1/16" NPT Outlets (16715NOS): The same proven form factor, but with smaller 1/16" NPT outlet threads — the go-to choice when using fine-thread nozzle fittings or smaller-diameter distribution lines.
• Showerhead Distribution Block (16752NOS): A step up in plumbing flexibility, this block features a 6 AN male inlet and four 6 AN male outlets with included adapter fittings, all in a black anodized aluminum body. The showerhead design is well-suited to higher-flow applications and AN-based plumbing setups.
• Professional Fogger Billet Blocks (16714NOS and variants): Used in NOS's Professional Fogger direct port kits, these blocks are machined from billet aluminum and bright-dip anodized — blue for the nitrous side and red for the fuel side — making it impossible to mix up your plumbing under the hood.

Finish Options and Fitment Notes

The standard NOS distribution blocks are available in a black anodized finish, but a highly polished show-quality finish is also available for builders who want underhood presentation to match performance. Note that fittings are sold separately on most configurations, giving builders the freedom to match their specific line sizes and routing needs. NOS's consistent use of NPT and AN thread standards means these blocks integrate cleanly with the broader NOS ecosystem of nozzles, lines, and solenoids.

Whether you're building a weekend bracket car or a serious direct port race system, NOS distribution blocks deliver the precision, materials quality, and fitment flexibility that the brand has staked its reputation on for over four decades.