Chevrolet Corvair engine 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.

Due to the greater thermal expansion of aluminum, hydraulic valve lifters were used to maintain correct lash as the engine expanded. These were trouble free and did not require periodic adjustment. Tuning issues related to the dual (or quadruple) carbs in non-turbocharged Corvairs sometimes led to erroneous diagnosis of valve issues in Corvairs- in fact, the Corvair had top quality valve materials in all models and valve jobs were almost never required. In fact, the valve train in most engines usually functioned perfectly for the life of the car.

Early engines were subject to occasional 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 and redesigning the gasket material and cross section, eliminating any issues.

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.

To address fuel slosh and cut-out issues in very hard cornering, some owners acquired 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. 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. This modification was especially ill-suited to models with Powerglide.

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. Engine temperatures on lower performance Corvairs with the AIR system were comparable to the Turbocharged models in some situations- head temperatures under full throttle could exceed 600F.