Spectre Coupler/Reducer 4in. to 3.5in. (PVC) - Black

The Spectre Coupler/Reducer 4in. to 3.5in. (PVC) in Black (part number 9741) is a step-down connector that transitions between a 4-inch and a 3.5-inch intake tube, air box outlet, or ducting component in naturally aspirated applications. The 9741 eliminates the need to fabricate a custom adapter or source a hard-to-find OEM reducer, making it a practical solution for cold-air intake builds, air box modifications, and replacement of cracked or deteriorated factory couplers. Included stainless steel worm-gear clamps ensure a leak-free, rattle-resistant connection at both ends. Not for use on pressurized (turbocharged or supercharged) systems.

Features and Benefits

• Transitions from 4-inch to 3.5-inch diameter for intake tube diameter changes
• PVC construction is flexible, vibration-resistant, and easy to install in tight spaces
• Black finish integrates cleanly with aftermarket cold-air intake systems
• Includes stainless steel worm-gear hose clamps for both ends
• Eliminates the need for custom fabrication when connecting mismatched tube diameters
• Compatible with aluminum, steel, ABS, and plastic intake tubing at the specified diameters
• Durable PVC material resists cracking from heat cycling in under-hood environments
• Spectre Performance quality ensures consistent wall thickness and dimensional accuracy

Specifications

What's Included

• 1 x Spectre 9741 PVC reducer coupler (4in to 3.5in ID, black)
• 2 x Stainless steel worm-gear hose clamps (one per end)

Frequently Asked Questions

What tube sizes does the Spectre 9741 connect?
The 9741 has a 4-inch ID on the large end and a 3.5-inch ID on the small end, designed to transition between these two common intake tube diameters.

Can the Spectre 9741 be used on a forced-induction vehicle?
No. The 9741 is a PVC coupler rated for naturally aspirated applications only. It is not designed for pressurized intake systems. Use a silicone reducer rated for boost pressure on turbocharged or supercharged vehicles.

Does the 9741 come with hose clamps?
Yes. The Spectre 9741 includes two stainless steel worm-gear hose clamps, one for the 4-inch end and one for the 3.5-inch end.

What is the length of the Spectre 9741?
Spectre describes the 9741 as approximately 3 inches in length. Confirm dimensions for your specific fitment requirements before ordering.

Will the 9741 work with an aluminum intake tube?
Yes. PVC couplers are compatible with aluminum, mild steel, ABS plastic, and similar tube materials. The worm-gear clamps grip the tube OD regardless of material.

Is the 9741 reversible (can the 3.5in side face upstream)?
Physically yes, but for proper airflow management the reducer should be oriented with the larger end toward the air source and the smaller end toward the engine, unless your specific intake design requires otherwise.

How do I prevent the Spectre 9741 from leaking at the joints?
Ensure both tube ends are inserted fully into the coupler ends before tightening the clamps. Position each clamp over the coupler-tube overlap zone and tighten evenly to 30-35 in-lb. Avoid over-tightening, which can distort the PVC.

Can I use the 9741 to connect an aftermarket air filter to a stock airbox outlet?
Yes, if the airbox outlet measures 4 inches OD and the filter inlet measures 3.5 inches OD (or vice versa). Confirm the OD dimensions of both components match the ID of the corresponding coupler end before installation.

Installation Instructions

1. Confirm the tube OD dimensions at both connection points match the 4in and 3.5in ends of the 9741.
2. Slide a hose clamp over each tube end before inserting into the coupler.
3. Insert the 4-inch tube fully into the large end of the Spectre 9741.
4. Insert the 3.5-inch tube fully into the small end of the coupler.
5. Position each hose clamp over the coupler-to-tube overlap zone on each side.
6. Tighten both clamps evenly until snug, without over-compressing the PVC walls.
7. Inspect both joints for gaps and verify the assembly is seated straight before starting the engine.

Proposition 65 Warning: This product can expose you to chemicals including Diisononyl Phthalate (DINP), which is known to the State of California to cause cancer. For more information, go to www.P65Warnings.ca.gov.