This inlet needle and seat assembly features a titanium needle paired with a 0.150" seat — one of the largest seat sizes Holley offers — for excellent sealing and quick response to changes in fuel flow rate.
Specifications:
- Seat Size: 0.150"
- Needle Material: Titanium
- Adjustable: Yes
- Fuel Compatibility: Racing fuels containing benzine, acetone, and alcohol
- Warranty: Manufacturer's Limited 90-Day Warranty
- Part Number: 6-521
FAQ
What seat size does the 6-521 use?
A 0.150" seat, one of the largest sizes available for this needle and seat design.
What is the needle made of?
Titanium, which responds quickly to changes in fuel flow and provides excellent sealing.
Is this needle and seat adjustable?
Yes.
Is it compatible with racing fuel?
Yes, it's compatible with racing fuels that contain benzine, acetone, and alcohol.

