The Corvair's innovative flat-6 engine

The Chevrolet Corvair engine was a flat-6 piston engine used exclusively in the 1960s Chevrolet Corvair automobile. It was a highly unusual engine for General Motors: It was air-cooled, used a flat design, with aluminum heads (incorporating integral intake manifolds) and crankcase, and individual iron cylinder barrels. The heads were modeled after the (excellent) standard Chevrolet overhead valve design, with large valves operated by rocker arms, actuated by pushrods run off a camshaft in the crankcase operating hydraulic valve lifters (which eliminated low temperature valve clatter otherwise seen with that much aluminum in the engine, due to its high degree of thermal expansion). Image File history File links Download high resolution version (1024x768, 141 KB) This isnt the turbo, this is the low end 2 carb engine. ... Image File history File links Download high resolution version (1024x768, 141 KB) This isnt the turbo, this is the low end 2 carb engine. ... The Chevrolet Corvair was a rear-engined automobile produced by the Chevrolet division of General Motors from 1960 to 1969. ... The flat-6 engine of the Honda Valkyrie motorcycle A flat-6 is a 6 cylinder configuration of a flat engine or boxer engine. ... Chevrolet, or Chevy for short, is a brand of automobile, now a division of General Motors. ... The flat-6 engine of the Honda Valkyrie motorcycle A flat-6 is a 6 cylinder configuration of a flat engine or boxer engine. ... Components of a typical, four stroke cycle, DOHC piston engine. ... The 1960s decade refers to the years from 1960 to 1969, inclusive. ... The Chevrolet Corvair was a rear-engined automobile produced by the Chevrolet division of General Motors from 1960 to 1969. ... General Motors Corporation (NYSE: GM), also known as GM, is an American automobile maker with worldwide operations and brands including Buick, Cadillac, Chevrolet, GMC, Holden, Hummer, Opel, Pontiac, Saturn, Saab and Vauxhall. ... Engine cooling is the process of cooling an engine by using either air or liquid. ... A flat engine is an internal combustion engine in which the cylinders are arranged in two banks on either side of a single crankshaft so that the motion of all the pistons is in a single plane. ... Aluminum is a soft and lightweight metal with a dull silvery appearance, due to a thin layer of oxidation that forms quickly when it is exposed to air. ... In automotive engineering, an intake manifold or inlet manifold is a part of an engine that supplies the fuel/air mixture to the cylinders. ... Crankshaft Continental engine marine crankshafts, 1942 Crankshaft is also the name of a comic strip about an old, curmudgeonly bus driver. ...

The flat horizontally opposed ("flat engine") air-cooled engine design, previously used by Volkswagen and Porsche as well as Lycoming aircraft engines, offered many advantages. Unlike inline or V designs, the horizontally opposed design made the engine inherently mechanically balanced, so that counterweights on the crankshaft were not necessary, reducing the weight greatly. Eliminating a water-cooling system further reduced the weight, and the use of aluminum for the heads and crankcase capitalized on this weight reduction; so that with the use of aluminum for the transaxle case, the entire engine/transaxle assembly weighed under 500 pounds. In addition, the elimination of water-cooling eliminated several points of maintenance and possible failure, reducing them all to a single point; the fan belt. As with the Volkswagen and Porsche designs, the low weight and compact but wide packaging made the engine ideal for mounting in the rear of the car, eliminating the weight and space of a conventional driveshaft. A flat engine is an internal combustion engine in which the cylinders are arranged in two banks on either side of a single crankshaft so that the motion of all the pistons is in a single plane. ... Volkswagen (pronounced folksvagen; meaning: peoples car; also known as VW or V-Dub) is an automobile manufacturer based in Wolfsburg, Germany in the State of Lower Saxony. ... Porsche (), properly pronounced as a two syllable word (porsh-eh, IPA: ) , is a German manufacturer of sports cars, founded in 1931 by Ferdinand Porsche, the engineer who created the first Volkswagen. ... For other meanings of Lycoming, please see Lycoming (disambiguation). ... Crankshaft, pistons, and flywheel Continental engine marine crankshafts, 1942 For the comic strip about an old, curmudgeonly bus driver, see Crankshaft (comic strip). ...

Two years after its 1960 debut, the Corvair engine gained another unusual attribute: it was the second production engine ever to be equipped from the factory with a turbocharger, released shortly after the Oldsmobile Jetfire V8. 1960 (MCMLX) was a leap year starting on Friday (the link is to a full 1960 calendar). ... Air foil bearing-supported turbocharger cutaway made by Mohawk Innovative Technology Inc. ... The final Oldsmobile Logo, an update of the Rocket theme used in various forms since 1948, debuted in the mid-1990s until the final Olds rolled off the line in 2004. ... The 1967 Toronados 425 V8, the first front-wheel drive V8 application. ... The Liberty V8 aircraft engine clearly shows the configuration A V8 engine is a V engine with eight cylinders. ...

Aircraft hobbyists and small volume builders, perhaps seeing the Corvair engine's similarity to Lycoming aircraft engines, very quickly began a cottage industry of modifying Corvair engines for aircraft use, which continues to this day. The Corvair engine also became a favorite for installation into modified Volkswagens and Porsches, as well as dune buggies and homemade sports and race cars. It has been suggested that this article or section be merged with Domestic system. ...

140

The initial Corvair engine displaced 140 in³ (2.3 L) and produced 80 hp (60 kW). The high performance "Turbo air" version produced 95 hp (70 kW).

145

In 1961, the engine received its first increases in size via a larger bore. The engine was now 145 in³ and the base engine was said to produce the same 80 hp (60 kW), but 84 hp (63 kW) if equipped with the optional automatic transmission. The new high performance engine was rated at 98 hp (73 kW). In 1962 the high performance engine was rated at 102 hp (76 kW) and the Spyder model became available featuring a turbocharged engine rated at 150 hp (112 kW). The turbocharger was mounted on the right side of the firewall behind the rear seat, fed by both exhaust manifolds; a single sidedraft carburetor mounted on the left side of the firewall fed directly into the turbocharger's intake, with a chromed pipe leading from the turbocharger's outlet to what would otherwise be the carburetor mounting pads on the intake manifolds, which were integral parts of the heads. The turbocharged heads received some valve upgrades to improve durability.

164

The engine was stroked out to 164 in&sup3 (2.7 L) for 1964. Power output was boosted to 95 hp (70 kW) for the base model and 110 hp (80 kW) in the high performance normally aspirated engine, while the Turbocharged engine remained rated at 150 hp for this year. This increase in stroke was the maximum the engine could tolerate, to the point that the bottoms of the cylinder barrels had to be notched to clear the big end of the connecting rods, while the bottom piston rings at the lowest point of the piston travel actually passed over these notches. This in turn required that the gaps in the piston rings be aligned so as not to catch onto the edge of the notches, a fact unfortunately not immediately obvious to all beginning Corvair engine rebuilders. For the Nintendo 64 emulator, see 1964 (Emulator). ... Piston ring A piston ring is an open-ended ring that fits into a groove on the outer diameter of the piston. ...

For the 1965 model year, all engines had the head gasket area between the cylinder and the head widened, in response to complaints of frequent head gasket failure. A 140 hp (104 kW) version with 4 single barrel carburetors was introduced in 1965; because this became the base engine for the Corsa model, it was unofficially known as the Corsa engine. The carburetors consisted of a single barrel primary and a single barrel secondary on each head, connected by a progressive linkage; in addition, the heads featured higher compression ratio, and the cars received dual exhaust systems. Engines supplied with the automatic transmission were equipped with a camshaft identical to that in the lower end (95 hp) two carburetor engine, while those supplied with manual transmissions got the camshaft out of the higher end (110 hp) two carburetor engine. This engine became optional when the Corsa line was dropped, in 1967. Chevrolet sold 279 of these engines in the 1967 model year, 232 with manual transmissions, and 47 with Powerglide transmissions. Only six were sold with the four carburetor engine and the AIR injection system required by California emissions standards. These figures include 14 Yenko Stingers and 3 Dana Chevrolet variants of the Stinger. Stromberg side-draft carburetor The carburetor (American spelling, a. ... 1965 (MCMLXV) was a common year starting on Friday (the link is to a full 1965 calendar). ... The word emission generally means sending something out. ...

The turbocharged engine now developed 180 hp (134 kW). Contemporary reviews describe a similarity in power between the turbocharged and four-carburetor engines throughout the low and mid rpm range, with the turbocharged engine being superior only on the top end. Enthusiast publications, however, began to describe how to modify the turbocharged engine to deliver more power "off the line".

Problems

The Corvair engine design was so unique that good dealer service and maintenance was spotty. Mechanics, unused to the aluminum head and crankcase, would frequently overtighten threaded fasteners and spark plugs, stripping the threads out of the aluminum, requiring extensive repair. This article or section should include material from Spark gap A spark plug is an electrical device that fits into the cylinder head of some internal combustion engines and ignites compressed aerosol gasoline by means of an electric spark. ...

Due to the greater thermal expansion of aluminum, valve clearances had to be measured at operating temperature. When they were measured on a cold engine, engines frequently and incorrectly were diagnosed as needing "valve jobs" early in their life. In fact, the valve train in most engines usually functioned perfectly for well over 100,000 miles. In physics, thermal expansion is the tendency of matter to increase in volume or pressure when heated. ...

Early engines were subject to frequent failures of the head gasket, between the heads and the cylinder barrels; this was addressed in later models by increasing the width of the sealing area.

The large cooling fan located on top of the engine required the fan belt to bend from the vertical plane of the crankshaft to the horizontal plane of the fan, causing additional stress. Chevrolet engineers designed a unique fan belt, which many owners and dealers replaced with an inappropriate design. The correct fan belt, properly installed to proper tension, worked well, while other belts even of proper size installed loose or tight would break frequently, giving the engine fan and belt design an undeserved bad reputation. Since failure of the cooling fan on an air-cooled engine leads to immediate overheating much more quickly than in a water-cooled engine (within 15 seconds at the high RPMs when the belts were likely to fail), mechanically inclined owners would routinely carry a spare belt and the 9/16 inch box wrench needed to change the belt, in addition to adding a large and eye catching warning light in parallel with the normally sized factory generator/alternator warning light. Aftermarket manufacturers made available differently sized pulleys which reduced the fan speed to 1.3 or 1.2 times engine speed, rather than the stock 1.5; this reduced the tendency to throw or break a fan belt for engines which spent most of their time at higher RPMs.

The pushrods were located below the cylinders, each in a separate metal tube between the crankcase and the head; these tubes also served to return oil from the head to the crankcase, and were fitted with neoprene O-rings at each end. After a short time, the neoprene exposed to the intense heat of the head lost resilience and developed a tendency to leak oil which became characteristic of Corvairs; unfortunately, since engine cooling air was diverted to the interior heater, this caused an unpleasant odor. Improved elastomer O-rings with much greater durability became available from aftermarket suppliers. A pushrod engine or overhead valve (OHV) engine is a type of piston engine that places the camshaft below the pistons (usually beside and slightly above the crankshaft in a straight engine or directly above the crankshaft in the V of a V engine) and uses pushrods or rods to... Neoprene is the DuPont Chemical trade name for a family of synthetic rubbers based on polychloroprene. ... Typical O-ring and application An O-ring is a loop of elastomer with a round (o-shaped) cross-section used as a mechanical seal. ...

In the original stock high performance four carburetor engine, only the two primary carburetors were equipped with idle circuits, for simplicity in tuning. However, with the progressive nature of the linkage, if the engine did not spend much time near full throttle there would be no fuel flowing through the secondary carburetors; as a result, the stagnant gasoline in their float bowls would continuously evaporate and leave a residue which built up, eventually completely destroying the carburetor. In the later versions of the engine, idle circuits were included in all four carburetors to prevent this problem, and there was a great deal of retrofitting and replacement of the older secondaries by owners. However, this in turn required that all four idle adjustments be balanced for a tuneup, which could be a problem in itself.

The progressive throttle linkage of the four barrel model was constructed simply and cheaply with rods simply passing through holes in bell cranks, rather than Heim joints; as a result it rapidly became imprecise and grew even worse with wear, making tuning the engine an exercise in futility. Some owners laboriously modified the linkage with precision components, but more purchased an aftermarket kit to rotate the carburetors through ninety degrees and attach the now colinear throttle shafts of the two carburetors on each side together, thereby greatly simplifying the linkage, as well as eliminating the problem of the secondaries becoming clogged from lack of use, mentioned above. However, this also eliminated the progressive feature of the stock carburetor linkage, so that performance could not be optimized both at low to midrange rpm and at high rpm.

Other owners replaced the four single-barrel carburetors with a single four-barrel carburetor, centrally mounted on a manifold with four long arms that attached to the original carburetor mounting pads on the heads. While this caused the carburetor and manifold to be slow to warm up to operating temperature and therefore caused problems with flooding and cold temperature operation, it eliminated linkage problems, simplified tuning the carburetor, and provided access to the large variety of four-barrel carburetors available on the market.

A factor which would have, in itself, led to the demise of the air cooled engine design was the rapid and relatively large temperature variation of the air-cooled engine with variations in load and rpm; this would have made meeting the upcoming emissions requirements of the 1970s difficult. The head temperature gauge with which the Corsa was equipped would visibly swing up and down as the car traveled between sunlit and shaded portions of the highway. The word emission generally means sending something out. ... The 1970s decade refers to the years from 1970 to 1979, inclusive. ...

Corvair engines swapped into Volkswagens

Initially, the cooling fans were designed with a twist to the vanes, so that they were only efficient when rotating in the correct direction. Early on, however, the vanes on the fan became vertical and radial, so that the fan functioned identically in either rotation. Whatever the reason for this change, one effect was that the engine could easily be configured to run in the direction opposite from stock. This proved useful for those who swapped the engine into Volkswagen Beetles and dune buggies, since the Corvair engine's normal direction of rotation was opposite to that of the Volkswagen (and most other automobiles). Otherwise, the ring gear of the Volkswagen differential had to be flipped over by 180 degrees to allow the transmission's forward and reverse directions to be correct. The VW Type 1, which was called the Beetle or Bug or Käfer (in German), is a small family car, the best known car of Volkswagen, one of the best known cars from Germany, and one of the most recognisable and distinctive cars in the world. ... Dune buggy A dune buggy is a recreational vehicle having big wheels and tires designed for use on sand dunes or beaches, especially a light vehicle with a modified engine mounted on an open chassis. ... A differential can mean one of several things: Differential (mathematics) Differential (mechanics) Differential signaling is used to carry high speed digital signals. ...

This swap was fairly common at the time, with the Corvair engine serving to give a power boost to Volkswagen Beetles, dune buggies, and Karmann Ghias. Excessively vigorous use of first gear would break the transaxle (the prudent driver would avoid first gear altogether), and the engine cover of the Karmann Ghia would not close completely with a Corvair engine in place, but otherwise the swap was relatively problem free, as such things go. The Karmann Ghia is a two-seater sports car marketed by Volkswagen, designed by the Italian firm Ghia, and built by German coach builder Karmann. ... A transaxle, in the automotive field, is a component that combines the functionality of the transmission, the differential and the drive axle into one integrated assembly. ...

Trivia and arcana

Many Corvair engine fans acquired a second life after the demise of their engines, mounted bottom side out on the outside of the wheels of Corvettes involved in road-racing, in order to pull air through the brakes and keep them cool. Lightweight and cheap, they were perfectly sized. French steam corvette Dupleix (1856-1887) Canadian corvettes on antisubmarine convoy escort duty during World War II. A corvette is a small, maneuverable, lightly armed warship, smaller than a frigate. ... For other uses, see Brake (disambiguation). ...

The single carburetor on each head of the two carburetor engine was not mounted symmetrically in the center of the intake manifold, where it might be intuitively placed, but offset from the center, between the middle and end cylinders. Although sometimes erroneously cited as an engineering error, this was in fact an example of clever attention to detail; had the carburetor been placed in the center of the manifold, the center cylinder would have received a significantly greater air/fuel charge then either end cylinder. Instead, the carburetor was situated so that the firing order required the air flow to reverse itself when filling either of the nearer cylinders, whereas the airflow to the far cylinder was merely an extension of the airflow to the center cylinder, which was just prior in the firing order. This allowed for a more balanced filling of the three cylinders, and smoother operation. In automotive engineering, an intake manifold or inlet manifold is a part of an engine that supplies the fuel/air mixture to the cylinders. ...

High performance parts manufacturer Edelbrock made available a set of larger bore aluminum cylinder barrels (with cast iron liners to withstand wear); when combined with their aluminum pushrods, the rate of thermal expansion of all parts of the valve train became compatible, so that solid valve lifters could be used, rather than the hydraulic lifters required by the stock cast iron cylinders. This in turn allowed the engine to run to higher RPMs; in conjunction with the increased torque resulting from the increase in cylinder bore, this resulted in a substantially more powerful engine. Edelbrocks Corporate Headquarters in Torrance, California Edelbrock Corporation is a California-based specialty performance automotive and motorcycle aftermarket parts manufacturer. ...

In addition, "stroker" crankshafts with longer stroke were quickly made available for the original engine. When Chevrolet increased the stroke of the stock engine, however, there was no longer room to increase it any further.

Immediately after the car became available with the original two carburetor engine, a number of manufacturers began to sell conversion kits for attachment of four carburetors, with either two stock carburetors, two of the ubiquitous Stromberg 97 carburetors, or a Rochester two barrel carburetor for each bank of cylinders. The means of attachment varied from simple two into one adapters, to machining off the entire top surface of the intake manifold (cast as part of the head), enlarging the internal passages of the manifold, and attaching a new upper surface incorporating the appropriate mounting pads for the new carburetors. Similarly, aftermarket manufacturers provided several means of supercharging the original engine, including belt driven centrifugal, axial flow, or rotary vane type compressors. Chevrolet, seeing the marketing opportunity available in these aftermarket options, of course went on to offer its own four carburetor and turbocharged versions. Stromberg is the name of: Stromberg (television) - a German television series Stromberg (Hunsrück) - a town in the district of Bad Kreuznach in Rheinland-Pfalz Stromberg (Westfalen) - a place in Oelde Stromberg (Landschaft) - a place in Baden-Württemberg This is a disambiguation page — a navigational aid which lists other pages that...

See also

• Chevrolet Corvair
• List of GM engines