164
The engine's stroke was increased from 2.6" to 2.94", resulting in a displacement of 164 cubic inches (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 (110 kW) 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.
For the 1965 model year, all engines had the head gasket area between the cylinder and the head widened, with a new design folded "Z" section stainless steel head gasket virtually eliminating any risk of head gasket failure. A 140 hp (104 kW) version with four single barrel carburetors, and a progressive linkage was introduced in 1965 as option L63 'Special High Performance Engine' and was standard equipment on the Corsa model. 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 a 9.25:1 compression ratio, and the cars received dual exhaust systems. Engines supplied with the automatic transmission after spring 1965 were modified with a camshaft from the 95 horsepower (71 kW) base engine, and a special crankshaft gear that retarded its timing 4 degrees- the former to increase torque and smooth the idle with the Powerglide transmission, the latter to restore some of the peak horsepower lost at higher engine speeds by the economy contoured camshaft with short timing.
1966 engines were basically carryover from the 1965 models, however Corvairs sold in California (except turbocharged models) now featured the General Motors Air Injection Reactor System (AIR), an emissions control system consisting of an engine driven air pump that drew filtered air from the air cleaner, and injected a metered amount into the exhaust manifolds via tubing to promote complete oxidation and combustion of exhaust gasses to lower emissions. Specially calibrated carburetors and slight changes to the ignition timing and advance curves were part of the package. The AIR system had an unfortunate effect of substantially raising exhaust gas, valve and head temperatures, particularly under heavy loads and this was a drawback on the Corvair where engine cooling could not be easily improved to cope with the higher temperatures. Nonetheless, performance and drivability were not noticeably affected in most circumstances. In 1968, all Corvair (and other GM) engines got the AIR system for every market. The combined heat load imposed by the AIR system, along with air conditioning, made air conditioning unavailable as an option after 1967, and on all earlier Corvairs with the AIR system.
The 140 hp (100 kW) engine was officially discontinued for '67, but became optional in 1967 as COPO 9551-B, not a regular production option. 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. Due to demand, the 140 hp (100 kW) engine returned as an RPO for the 1968 model year, and was available until the end of the Corvair's run in spring 1969.
Both the 140 hp (100 kW) engines and the turbocharged engines had many special quality features not shared with lesser Corvairs- Moly insert top rings, stellite tips and faces on the valves, a Tufftrided (cold gas hardened) crankshaft, and Delco Moraine '400' aluminum engine bearings- the quality of the 140 hp (100 kW) Corvair engine for materials is directly comparable to the Rolls Royce V8 of that era, item for item. The upgrade was inexpensive for the $79 premium it commanded over the basic 95 hp (71 kW) engine. Performance of the 140 hp (100 kW) engine was good, with a 5200 rpm peak horsepower output, it offered road performance in a Corvair comparable to contemporary Cadillac models of the day.
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 when it was possible to sustain boost continuously. The turbocharged engine's long suit was highway acceleration, flooring the accelerator at turnpike speeds produced strong acceleration in the upper speed ranges as the turbocharger began to boost, reaching manifold pressures approaching 15 PSI. No wastegate was used on the Corvair turbocharged engine; boost was controlled by careful balancing of exhaust restriction, mostly via the muffler, and intake restrictions from the smallish Carter YH carburetor used. Pre-ignition and knock under boost was controlled using a novel 'pressure retard' device, essentially a modified vacuum advance device, on the specially curved distributor, as boost pressures built, ignition advance was progressively reduced to preclude detonation.
Read more about this topic: Chevrolet Corvair Engine