The below oils are great for Corvair and similar engines

AMSOIL Synthetic 10W-40 Motor Oil is specially formulated to provide superior protection and performance in a wide variety of demanding applications. By incorporating high-quality synthetic base stocks and a superior high-zinc additive package, AMSOIL Premium Protection Oil exceeds the needs of large and small gasoline or diesel engines in cars, motorcycles, trucks, motor homes, maintenance equipment, heavy equipment, street rods and marine applications. It is ideal for high-mileage vehicles, vehicles with flat-tappet cams and high-stress vehicles subject to hot temperatures, heavy hauling, trailer pulling or off-road use. AMSOIL Premium Protection Oil resists oxidation, neutralizes acids, inhibits corrosion, reduces wear and protects against deposits. It provides the extra anti-wear protection required by engines with flat-tappet cams and high-tension valve springs. AMSOIL Synthetic 10W-40 Premium Protection Motor Oil offers flexibility and performance beyond conventional oil for convenience and trouble-free operation. AMSOIL, the leader in automotive synthetic lubrication, produced the world’s first API qualified synthetic motor oil in 1972. Trust the extensive experience of AMSOIL The First in Synthetics® to do the best job protecting your engine. Provides Superior Wear Protection AMSOIL Synthetic 10W-40 Premium Protection Motor Oil is a high viscosity oil engineered to protect against metal-to-metal contact. It resists viscosity shear and is formulated with a heavy treatment of zinc and other anti-wear additives for excellent protection of gears, bearings, cam lobes and other high-pressure components in engines and transmissions. AMSOIL Premium Protection Synthetic Motor Oil helps extend engine life. Exceeds the Requirements of Wet Clutch Transmissions AMSOIL Premium Protection Synthetic Motor Oil contains no friction modifiers, making it ideal for motorcycles, maintenance equipment and other wet clutch transmission applications. Formulated to prevent clutch glazing and slippage, it helps insure smooth clutch engagement and long term, dependable transmission operation. AMSOIL Synthetic 10W-40 Motor Oil reduces clutch wear for extended transmission life. Resists Oxidation and High Temperature Breakdown AMSOIL Premium Protection Synthetic Motor Oil is specifically formulated to overcome the thermal deficiencies common to conventional petroleum oils. Volatilization (burn-off), oxidation and excessive deposit formation from high heat are greatly reduced. Viscosity thickening is controlled and engines run cleaner, promoting cooler operation and long engine life in air- or liquid-cooled engines.

AMSOIL Z-ROD™ Synthetic Motor Oil is specially engineered for classic and high-performance vehicles. It features a high-zinc formulation to prevent wear on flat-tappet camshafts and other critical engine components, along with a proprietary blend of rust and corrosion inhibitors for added protection during long-term storage. Z-ROD Synthetic Motor Oil is designed to perform on the street and protect during storage. AMSOIL, the leader in automotive synthetic lubrication, produced the world’s first API-qualified synthetic motor oil in 1972. Trust the extensive experience of AMSOIL, the First in Synthetics®, to do the best job protecting your engine. Protects Flat-Tappet Cams The lifters and cam lobes on flat-tappet camshafts common to classic and high performance vehicles slide rapidly against one another, producing high friction and heat. The friction between the two components can eventually wear down the cam and affect valve operation, ultimately resulting in lost engine power and reduced efficiency. In addition, these areas are splash-lubricated rather than pressure lubricated like other areas of the engine, which adds extra strain on anti-wear additives like the zinc and phosphorus in zinc dialkyldithiophosphate (ZDDP). AMSOIL Z-ROD Synthetic Motor Oil is formulated with high levels of ZDDP to protect flat-tappet cams, lifters, rockers and other areas susceptible to wear. Its high-zinc, high-phosphorus formulation provides the extra wear protection these critical splash-lubricated components require. Provides Long-Term Protection from Rust & Corrosion AMSOIL Z-ROD Synthetic Motor Oil is formulated with a unique blend of rust and corrosion inhibitors to ensure maximum protection during long-term storage. To prove its effectiveness, AMSOIL submitted Z-ROD Synthetic Motor Oil to the Standard Test Method for Rust Protection in the Humidity Cabinet (ASTM D-1748). This test evaluates the rust-preventative properties of oil under high-humidity conditions, similar to those faced by a covered hot rod in a damp garage. The metal coupon treated with AMSOIL Z-ROD Synthetic Motor Oil showed no signs of oxidation after 192 hours, while the coupon treated with a leading competitor’s product failed the test after 24 hours. APPLICATIONS AMSOIL Z-ROD Synthetic Motor Oil is recommended for older or modified engines requiring either 10W-30 or 20W-50 motor oil. Z-ROD Synthetic Motor Oil meets API SL and earlier specifications, allowing for increased levels of anti-wear additives. ZDDP levels in Z-ROD Synthetic Motor Oil exceed the limits of API SM and newer specifications.