The Castair P2B80-13/8 is a 2-groove (2B) replacement motor pulley with a fixed 1-3/8" bore and 8.0" outer diameter. This is one of the larger motor pulleys in the Cast Air 2B fixed-bore lineup, used when the application calls for higher pump RPM — and therefore more delivered CFM — from the same motor. If your 8.0" OD pulley is cracked, groove-worn, or damaged, this is the direct replacement.
Note: Cast Air did not provide a dedicated manufacturer product page for this pulley. Specifications are drawn from the product listing and standard 2B pulley conventions. Contact us to confirm fitment for your specific compressor before ordering.
Why the 8.0" OD Pulley?
Motor pulley OD controls pump speed. A larger motor pulley drives the pump faster relative to motor RPM. An 8.0" motor pulley paired with a 14" pump flywheel produces a drive ratio of approximately 1.75:1 — meaning a 1,750 RPM motor drives the pump at roughly 1,000 RPM. This is toward the high end of the operating range for Cast Air single-stage pumps and delivers maximum CFM from those pump designs. The 8.0" OD is typically found on compressors where the motor is sized to handle the increased pump load and heat that comes with higher RPM operation.
Pulley Specification Details
- Groove Profile: 2B (two B-section V-belt grooves)
- Bore Type: Fixed bore — 1-3/8" (1.375") shaft diameter
- Outer Diameter (OD): 8.0"
- Application: Motor-side pulley for belt-drive air compressors
- Compatibility: Castair belt-drive compressors with 1-3/8" motor shafts and B-section belts
- Part Number: P2B80-13/8
Fixed Bore Identification and Installation
The P2B80-13/8 is a fixed-bore pulley. It is machined with a 1-3/8" center bore and includes keyway slots and set screw holes for securing to the motor shaft. Installation is straightforward: slide onto the shaft, align the key, and tighten the set screw. The important thing is confirming you have a 1-3/8" motor shaft — neither larger nor smaller — before ordering, because a fixed bore pulley cannot be bored out or resized in the field.
Fixed Bore vs. Taper-Lock Selection
- Fixed bore (this pulley): One specific shaft size. No bushing required. Correct for direct replacement when original was also fixed bore 1-3/8".
- Taper-lock (SK/SD): Bushing-style hub adapts to multiple shaft diameters. Different installation method, different part number — not interchangeable with fixed bore.
- Verify your motor shaft diameter is exactly 1-3/8" before ordering this pulley.
When Does a Shop Need the 8.0" OD Pulley?
- Original motor pulley measured 8.0" OD with 1-3/8" bore and is worn, cracked, or damaged
- Rebuilding a Cast Air compressor that came factory-equipped with an 8.0" motor pulley
- Application requires higher pump RPM than smaller pulleys provide and the pump/motor combination is rated for it
- Tachometer confirms pump RPM is lower than spec — a replacement pulley of the correct OD restores the original drive ratio
2B Fixed-Bore 1-3/8" Motor Pulley Size Comparison
- P2B625-13/8 — 6.25" OD — $68.34 — lowest pump speed in the series
- P2B675-13/8 — 6.75" OD — $71.23 — standard mid-range OD
- P2B725-11/8 — 7.5" OD — $84.70 — larger, for increased pump RPM requirements
- P2B80-13/8 — 8.0" OD — $88.55 (this unit) — high-speed motor pulley for maximum CFM applications
- P2B875-13/8 — 8.75" OD — $103.95 — largest fixed-bore 1-3/8" option
Technical Specifications
- Part Number: P2B80-13/8
- Manufacturer: Cast Air (Castair)
- Groove Type: 2B (two B-section V-belt grooves)
- Bore: Fixed, 1-3/8" (1.375")
- Outer Diameter: 8.0"
- Bore Style: Fixed (keyway and set screw)
- Belt Section: B-section (two matched belts)
- Price: $88.55
- Manufacturer Data: Product page not available — specifications from product listing data
What Is Included
- 1x Castair P2B80-13/8 motor pulley
- Set screw(s) for shaft retention
B-section matched belts are not included. Determine the correct belt length based on your drive center distance.
Why Buy From Air Compressor Factory Direct?
We have stocked Cast Air replacement parts since 2016 and carry the full motor pulley lineup across OD sizes and bore styles. If you are not certain whether 8.0" is the correct OD for your specific compressor, call us before ordering — we can verify against your model number. Free shipping on all orders, free tech support, and full manufacturer warranty on every Cast Air part.
- Cast Air specialist since 2016
- Free shipping on all orders
- Free tech support — confirm fitment before you order
- Full manufacturer warranty
- Honest guidance on which OD fits your application
Call 866-217-0063 for quick answers and help!
