{"product_id":"castair-replacement-motor-pulley-hub-sk-shaft-8-38-od-3b-grooves","title":"Castair Replacement Motor Pulley Hub SK Shaft 8.38\" OD. 3B Grooves","description":"\u003cp\u003eThe Castair P3B838SK is a 3-groove (3B) motor pulley with SK taper-lock hub and 8.38\" outer diameter. It is the largest 3B SK-hub motor pulley in the Cast Air lineup, designed for compressor systems where three matched B-section belts are required and a larger motor pulley OD is needed to achieve the correct pump drive ratio. The SK hub accepts a range of standard SK bushings, so this pulley can be installed on motors with different shaft diameters by selecting the appropriate bushing.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eNote: Cast Air did not provide a dedicated manufacturer product page for this pulley.\u003c\/strong\u003e Specifications are drawn from the product listing and standard 3B SK-hub pulley conventions. Call us before ordering to confirm the correct SK bushing and belt combination for your specific application.\u003c\/p\u003e\n\n\u003ch2\u003eThe Largest 3B SK Motor Pulley in the Cast Air Lineup\u003c\/h2\u003e\n\u003cp\u003eAt 8.38\" OD, the P3B838SK drives the pump faster than the 6.15\" (P3B615SD) and 7.75\" (P3B775SK) options for any given motor RPM. Paired with a 14\" pump flywheel, this pulley produces a drive ratio of approximately 1.67:1 — meaning a 1,750 RPM motor drives the pump at about 1,048 RPM. This is within the upper normal range for Cast Air two-stage and heavy-duty single-stage pump designs. The three-groove configuration handles the drive torque that a larger motor pulley OD places on the belt drive system at higher pump speeds.\u003c\/p\u003e\n\n\u003ch3\u003ePulley Specification Details\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eGroove Profile:\u003c\/strong\u003e 3B (three B-section V-belt grooves)\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eHub Type:\u003c\/strong\u003e SK taper-lock (bushing required, sold separately)\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eOuter Diameter (OD):\u003c\/strong\u003e 8.38\"\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eApplication:\u003c\/strong\u003e Motor-side pulley for heavy-duty belt-drive air compressors\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eCompatibility:\u003c\/strong\u003e Cast Air belt-drive compressors using 3B SK-hub motor pulleys and B-section belts\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003ePart Number:\u003c\/strong\u003e P3B838SK\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eWhy This Pulley Requires Three Grooves\u003c\/h2\u003e\n\u003cp\u003eLarger OD motor pulleys drive the pump faster, which increases both the CFM output and the power demand on the drive system. At 8.38\" OD, the belt tension required to transmit the motor's torque without slipping exceeds what two B-section belts can reliably handle at the compressor's duty cycle. Three belts distribute the load — each belt carries less tension, runs cooler, and lasts longer. The pump flywheel must also be 3-groove for this to work. If your existing flywheel is 2-groove, the pulley and flywheel must be changed together.\u003c\/p\u003e\n\n\u003ch3\u003eSK Taper-Lock Hub — Installation and Bushing Selection\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003eThe SK hub requires a standard SK bushing bored to your motor shaft diameter\u003c\/li\u003e\n\u003cli\u003eCommon SK bushing bore sizes: 5\/8\", 7\/8\", 1\", 1-1\/8\", 1-3\/8\", 1-5\/8\", 1-7\/8\" — specify your shaft diameter when ordering\u003c\/li\u003e\n\u003cli\u003eInstallation: slide bushing on shaft, align key, hand-thread mounting screws through pulley into bushing flange, torque evenly\u003c\/li\u003e\n\u003cli\u003eRemoval: back screws out, thread into jack holes to push the taper apart\u003c\/li\u003e\n\u003cli\u003eThe SK bushing can often be reused when the motor is replaced, making this a long-service-life pulley assembly\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eWhen Does a Shop Need the P3B838SK?\u003c\/h2\u003e\n\u003cul\u003e\n\u003cli\u003eOriginal 8.38\" 3B SK-hub motor pulley is worn, cracked, or groove-damaged from belt failure\u003c\/li\u003e\n\u003cli\u003eRebuilding a heavy-duty Cast Air compressor to original drive specifications\u003c\/li\u003e\n\u003cli\u003eMotor replacement on a 3-groove drive system where the pulley is in good condition but the bushing bore needs to change for a different shaft size\u003c\/li\u003e\n\u003cli\u003ePump is running at confirmed low RPM (tachometer) and the motor pulley is identified as undersized for the application\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eCast Air 3B Motor Pulley Comparison\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eP3B615SD — 6.15\" OD — $105.88\u003c\/strong\u003e — SD hub, smaller OD, lower pump RPM\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eP3B775SK — 7.75\" OD\u003c\/strong\u003e — SK hub, mid-range OD\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eP3B838SK — 8.38\" OD — $132.83\u003c\/strong\u003e (this unit) — SK hub, largest in the 3B series, highest pump RPM\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eTechnical Specifications\u003c\/h2\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003ePart Number:\u003c\/strong\u003e P3B838SK\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eManufacturer:\u003c\/strong\u003e Cast Air (Castair)\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eGroove Type:\u003c\/strong\u003e 3B (three B-section V-belt grooves)\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eHub Type:\u003c\/strong\u003e SK taper-lock (bushing sold separately)\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eOuter Diameter:\u003c\/strong\u003e 8.38\"\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eBelt Section:\u003c\/strong\u003e B-section (three matched belts)\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003ePrice:\u003c\/strong\u003e $132.83\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eManufacturer Data:\u003c\/strong\u003e Product page not available — specifications from product listing data\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eWhat Is Included\u003c\/h2\u003e\n\u003cul\u003e\n\u003cli\u003e1x Castair P3B838SK motor pulley (SK hub)\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp\u003eSK bushing and three B-section matched belts are not included. Call us with your motor shaft diameter and drive center distance and we will help you source the complete assembly.\u003c\/p\u003e\n\n\u003ch2\u003eWhy Buy From Air Compressor Factory Direct?\u003c\/h2\u003e\n\u003cp\u003eHeavy-duty 3-groove SK-hub drive systems involve specific components — and ordering the wrong bushing bore or belt length means the compressor does not run right. We have been selling Cast Air parts since 2016 and know the product lineup well enough to help you avoid those mistakes. Free shipping, free tech support, and full manufacturer warranty on all Cast Air parts.\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eCast Air specialist\u003c\/strong\u003e since 2016\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eFree shipping\u003c\/strong\u003e on all orders\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eFree tech support\u003c\/strong\u003e — we identify the correct SK bushing for your shaft\u003c\/li\u003e\n\u003cli\u003e\u003cstrong\u003eFull manufacturer warranty\u003c\/strong\u003e\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eComplete drive system sourcing\u003c\/strong\u003e — we help you order the full replacement kit\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp\u003e\u003cstrong\u003eCall 866-217-0063 for quick answers and help!\u003c\/strong\u003e\u003c\/p\u003e","brand":"Cast Air","offers":[{"title":"Default Title","offer_id":53342574018773,"sku":"P3B838SK","price":245.66,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0622\/8466\/0949\/files\/MOTOR-PULLEYS-300x248_09fdefb0-29e9-4903-a1c9-1fd3ba641207.jpg?v=1772652782","url":"https:\/\/aircompressorfactorydirect.com\/products\/castair-replacement-motor-pulley-hub-sk-shaft-8-38-od-3b-grooves","provider":"Air Compressor Factory Direct","version":"1.0","type":"link"}