Structured digital documentation collection for the Continental R-670 and W-670 seven-cylinder air-cooled radial aircraft engines. This collection provides service manuals, overhaul instructions, parts catalogs, and operator documentation spanning 1943-1956 for all major variants of this legendary powerplant.

Definitive Collection with Free Lifetime Updates: This is a living collection that we continuously expand and refine. As we acquire additional Continental R-670/W-670 documentation, technical bulletins, or variant-specific materials, we update this collection and provide free lifetime updates to all purchasers. Your one-time purchase guarantees access to all future additions and improvements to this collection.

Historical Note

The Continental R-670 (military designation) and W-670 (civilian designation) series represents one of the most successful and widely-produced radial aircraft engines in aviation history, serving as the backbone of Allied pilot training during World War II and continuing in active service on vintage aircraft today.

Design Origins (1929-1934): Developed by Continental Aircraft Engine Company, a subsidiary of Continental Motors Company (founded 1905), the R-670 first ran in 1934 as a refined evolution of the earlier 7-cylinder A-70 engine. Continental had begun focusing on radial engines with the A-70 in 1929, and the R-670 utilized many of its installation dimensions but featured a larger bore (5.125 inches) for increased power output. The engine received Approved Type Certificate (ATC) No. 80 on August 21, 1933.

Wartime Service and Production (1941-1945): While civilian sales remained modest during the Great Depression, World War II transformed the R-670 into a mass-production powerplant. Over 25,000 units were manufactured to meet military demands, powering the vast majority of Allied primary training aircraft. More than 6,000 Boeing-Stearman PT-17 Kaydets (and Navy N2S variants) relied on the R-670-5 variant, making it the most common engine in the series. The engine also powered the Fairchild PT-23, Timm N2T Tutor, and numerous other trainers that prepared thousands of Allied pilots for combat operations.

Aircraft Applications: The R-670/W-670 powered an impressive range of military and civilian aircraft including the Boeing-Stearman PT-17/N2S Kaydet, Fairchild PT-23, Timm N2T Tutor, Waco Standard Cabin series (UEC, UIC, UKC, VKS), Waco Custom Cabin series (UOC, VQC), Waco F series (UPF-7), Cessna 190, Kellett K-2A/K-4 autogyros, and Grumman G-164 Ag Cat. The W670-9A variant was uniquely adapted for armored vehicles including the M3 Stuart tank and Landing Vehicle Tracked (LVT) Buffalo, featuring larger front crankshaft journals and thrust bearings to withstand ground vehicle stresses.

Designation Differences (R-670 vs. W-670): Between 1934 and 1936, Continental changed the factory designation from R-670 to W670 (or W-670). Generally, "R-670" (radial) was used for military procurement, while "W-670" was used in civilian contexts, though they were essentially the same engine family with variations in compression ratio (5.4:1 to 6.1:1), horsepower (210 hp to 250 hp), and later fuel injection systems.

Engineering Excellence: The engine earned its reputation through exceptional durability and operational flexibility. Weighing approximately 465 pounds while producing 220-250 horsepower, it offered outstanding power-to-weight ratio for its era. Designed to operate on low-octane fuel (73-80 octane), it proved ideal for wartime logistics when high-octane aviation fuel was reserved for combat aircraft. The engine operated reliably in every theater of war, from Arctic conditions to scorching desert environments.

Post-War Legacy and Current Status: Following World War II, thousands of surplus military trainers entered civilian service, with R-670/W-670 engines powering crop dusters, sport planes, and civilian training aircraft throughout the general aviation boom. Production continued through the 1950s before ending as turbine and horizontally-opposed engines became dominant. Today, the R-670/W-670 remains in active service on vintage and warbird aircraft, particularly the Boeing-Stearman PT-17 and Waco biplanes, which are staples of the vintage aviation community and frequent performers at airshows worldwide. The current Type Certificate holder is Continental Aerospace Technologies (formerly Continental Motors/Teledyne Continental) based in Mobile, Alabama.

Manuals Included in This Collection

• Continental R-670-4, -5, -6, -11 Aircraft Engine Service Manual (AN 02-40AA-2, 1 July 1943)
• Continental R-670-3, -4, -5 Aircraft Engine Service Manual
• Continental R-670-4, -5, -6, -11 Aircraft Engine Parts Catalog Manual (02-40AA-4, 1943)
• Continental R-670 Aircraft Engine Operator Manual
• Continental R-670-4, -5, -6, -11, -11A Aircraft Engine Service Manual (02-40AA-2)
• Continental R-670-4, -5, -6, -11, -11A Aircraft Engine Overhaul Manual (02-40AA-3, 1945)
• Continental R-670-3, -4, -5 Aircraft Engine Overhaul Manual (Technical Order No. 02-40AA-3, October 5, 1940, Revised 4-10-43)
• Continental W-670 Aircraft Engine Overhaul and Parts Catalog Manual (1956)
• Continental W-670 Aircraft Engine Overhaul Tools Catalog Manual
• Continental W-670 Aircraft Engine Operating and Maintenance Manual

This collection provides comprehensive coverage of all major R-670 and W-670 variants including the R-670-3, -4, -5, -6, -11, and -11A military models, plus civilian W-670 variants (W670-6A, W670-6N, W670-K, W670-M, W670-16, W670-17, W670-23, W670-24). Documentation spans from wartime military technical orders (1940-1945) through post-war civilian maintenance manuals (1956), capturing the engine's complete service evolution from military training operations to civilian applications.

Engineering Norms and Standards

Military Specifications and Certifications: The R-670 series was developed and certified under U.S. Army Air Forces specifications, with documentation published under joint authority of the Commanding General, Army Air Forces, the Bureau of Aeronautics, and the Air Council of the United Kingdom. Military technical orders were classified as "RESTRICTED - FOR OFFICIAL USE ONLY" and contained information affecting national defense under the Espionage Act (50 U.S.C., 31 and 32, as amended). These manuals reference AN (Army-Navy) standardized part numbers and military procurement specifications that governed wartime production.

Civilian Type Certificate Standards: The civilian W-670 series received Approved Type Certificate (ATC) No. 80 on August 21, 1933, certifying compliance with Department of Commerce aeronautical regulations. This certification established the legal airworthiness basis for civilian installations and continues to govern W-670 operations on certificated aircraft today.

Continental Engineering Practices: The R-670/W-670 incorporated Continental's established radial engine design philosophy, including aluminum alloy pistons made in permanent molds with unique oil control ring configurations (wider ring in third groove, compression ring serving as oil scraper below piston pin), enhanced cooling fin patterns on cylinder heads for improved heat management, Scintilla MN7-DF magnetos for dual ignition reliability, and single Stromberg NA-R6 carburetor (later upgraded to NAR6G in post-war variants). The W-670-9A armored vehicle variant featured specialized engineering modifications including larger front crankshaft journals and thrust bearings to accommodate ground vehicle installation stresses.

Technical Specifications: The engine is a 7-cylinder, 4-stroke air-cooled radial with 668 cubic inches (10.95 liters) displacement, bore and stroke of 5.125 in × 4.625 in (130.2 mm × 117.5 mm), compression ratios ranging from 5.4:1 (low-octane 65-73 octane fuel) to 6.1:1 (high-performance 240-250 hp versions), power output of 210 to 250 hp depending on model and compression ratio, fuel consumption of approximately 13 US gallons per hour at cruise, and oil consumption of approximately 0.4 US gallons (1.5 liters) per hour at cruise. The engine weighed approximately 465 pounds dry, providing exceptional power-to-weight ratio for its era.

Maintenance and Overhaul Standards: These manuals document Continental's prescribed maintenance intervals, inspection procedures, overhaul tolerances, and parts replacement criteria as established during the engine's production era. They include detailed torque specifications, clearance measurements, wear limits, and assembly procedures that defined proper maintenance practice for military and civilian operators from the 1940s through 1950s.

Specialized Documentation

Supplemental Type Certificates (STCs) and Performance Modifications: While these historical manuals document original factory specifications, the active R-670/W-670 fleet has benefited from numerous modern STCs and approved modifications. The W-670-23 conversion STC upgrades 220 hp models to 240 hp configuration, often including constant-speed propeller installations for improved climb and cruise performance. Mogas (automotive fuel) STCs from providers like Petersen Aviation allow operation on alcohol-free premium automotive gasoline, reducing lead fouling compared to 100LL Avgas. Additional performance modifications address the engine's historical reliability challenges through FAA-approved Parts Manufacturer Approval (PMA) parts.

Modern Reliability Upgrades: Contemporary overhaul practices incorporate significant improvements over original 1940s-1950s specifications. Roller main bearings replace original ball bearings (which were prone to repeated failure) by providing greater contact area and easier inspection capability. Improved oil seals using modern nitrile rubber or neoprene replace original leather seals in oil pumps and magneto drive gears, preventing moisture retention and gear corrosion. Shielded ignition harnesses (such as Skytronics systems) reduce radio interference for modern avionics integration while maintaining period-correct appearance. NAR6G carburetors replace older NAR6D models to eliminate acceleration "flat spots." Intake pipe quick drains and specialized lower-cylinder piston modifications (pistons lacking certain oil control grooves for cylinders No. 4 and 5) help prevent liquid lock, a common vulnerability in radial engines where oil pools in lower cylinders. Nu-Chrome or new steel cylinders, electronic ignition options (SureFly modules replacing one magneto), and modified engine baffle systems with rubberized seals facilitate regular maintenance.

Service Bulletins and Airworthiness Directives: Current Type Certificate holder Continental Aerospace Technologies (Mobile, Alabama) maintains the official airworthiness authority for R-670/W-670 engines. Operators of certificated aircraft should consult Continental Aerospace Technologies for current Service Bulletins, Airworthiness Directives, and continuing airworthiness requirements. Specialist overhaul facilities including Air Repair, Inc. and Radial Engines, Ltd. offer proprietary service bulletins covering modern enhancements such as stainless hose clamps, removable intake pipes, and modified tachometer housings for improved sealing.

Operational Notes and Pilot Guidance: The R-670/W-670's operational characteristics include high oil consumption (approximately 0.4 gallons per hour at cruise, considered normal for radial engines of this era), pre-flight procedures requiring manual propeller rotation to clear lower cylinders of accumulated oil (preventing hydraulic lock on startup), fuel flexibility allowing operation on 73-80 octane fuel (though modern operators typically use 100LL Avgas or approved mogas), and cooling management requiring careful attention to cylinder head temperatures, particularly in climb configurations. These manuals document original operating procedures and limitations as established during the engine's service life.

Where to Find Additional Documentation

Official Support: Continental Aerospace Technologies (formerly Continental Motors/Teledyne Continental), based in Mobile, Alabama, is the current Type Certificate holder for the R-670/W-670 series. Contact Continental Aerospace Technologies for current Service Bulletins, Airworthiness Directives, parts availability, and continuing airworthiness information for certificated aircraft installations. Their technical support department maintains the official engineering authority for these engines.

Historical Archives and Community Resources: The vintage aviation community provides extensive support for R-670/W-670 operators through specialized forums, type clubs, and enthusiast organizations. The Stearman Restorers Association and International Stearman Fly-In community offer extensive knowledge sharing among PT-17/N2S owners and restorers. The Waco Historical Society and Waco Classic Aircraft Corporation support Waco biplane operators with technical guidance and parts sourcing. Online forums including VAF (Vintage Aircraft Forum), Biplane Forum, and Warbirds of America chapters provide peer-to-peer technical discussions and operational experience sharing. The National Museum of the United States Air Force and other military aviation museums maintain archival collections of R-670 technical documentation and historical records.

Specialty Vendors and Overhaul Facilities: Several specialized facilities provide R-670/W-670 overhaul services, modern upgrades, and technical support. Air Repair, Inc. and Radial Engines, Ltd. are recognized specialists offering comprehensive overhaul services, PMA parts, proprietary modifications, and technical consulting. Online Aviation Library provides curated historical documentation collections including these factory manuals, parts catalogs, and technical orders. Additional specialty vendors supply PMA replacement parts, modern ignition systems, upgraded oil seals, and performance modification components approved for R-670/W-670 installations.

Format and Delivery

Delivery: Instant digital download upon purchase completion. Download links are provided immediately via email and through your Online Aviation Library account.

Format: High-resolution PDF files scanned from original military technical orders and manufacturer documentation. These are authentic historical documents preserved in digital format, maintaining original page layouts, technical illustrations, parts diagrams, and specification tables.

Compatibility: Compatible with all modern devices including Windows PC, Mac, iPad, Android tablets, and smartphones. Files can be stored locally, backed up to cloud storage, or printed for workshop reference.

Organization: Manuals are clearly labeled by variant, document type (Service Manual, Overhaul Manual, Parts Catalog, Operator Manual), and publication date for easy reference and archival organization.

Print-Friendly: Optimized for printing if you prefer physical copies for hangar or workshop use. High-resolution scans ensure clear reproduction of technical diagrams, parts illustrations, and specification tables.

Searchable: PDF format allows keyword searching within documents for rapid location of specific procedures, part numbers, or technical specifications.

Disclaimer

This item is sold for historical and reference purposes only. These are either original or copies of manuals used when these aircraft engines were in active military and civilian service, now transferred into electronic format. These manuals are not meant to be used for current update material for certification/repair, but make an excellent reference for the scholar, collector, restorer, or aviation enthusiast.

For current airworthiness requirements, Service Bulletins, Airworthiness Directives, and approved maintenance procedures for certificated aircraft, consult the current Type Certificate holder (Continental Aerospace Technologies) and applicable FAA regulations. The information is for reference only, and we do not guarantee the completeness, accuracy, or currency of any manuals.

Reference herein to any specific commercial products by trade name, trademark, manufacturer, or otherwise, is not meant to imply or suggest any endorsement by, or affiliation with that manufacturer or supplier. All trade names, trademarks and manufacturer names are the property of their respective owners.

Copyright: This digital compilation, structure, indexing and presentation are © Sicuro Publishing.