Chevy Small-block—1962 to 1998 Number 7
The 4.0-inch bore 350 variations 1967 to 1980 continued…
For the 1969 and the 1970 model years, the L46 was an option for the Corvette; this is a high-performance version of the base 350 engine. Its block casting number is 492, and it features 2.2/1.60-inch valve heads and has a high 11:1 compression ratio delivering 350 bhp (261 kW).
The LT-1 350 for the Corvette in 1970 was the pinnacle for this small-block. Solid lifters, a high 11.1:1 compression, a high output “178” crank, topped off with a CFM Holley carburetor on the aluminum intake and the rams’ horn manifold handling the low restriction exhaust, worked together to give it the edge. The Delco transistorized ignition allows the LT-1 to put out 370 bhp (272.1 kW) in the Corvette and 360 bhp (264.8 kW) in the Camaro Z/28 at 6000 rpm developing 380 lbs-ft. of torque at 4000 rpm, but the NHRA rated this engine at 425hp (312.6 kW). The LT-1 red lined at 6500 rpm, but the power begins to drop off at 6300 rpm. For 1971, this 350 engine has the compression dropped to 9:1, which now allowed the LT-1, in both the Vette and the Camaro, to develop 330 bhp (255 net hp; 242.7 kW) with a further drop in 1972 to 255 bhp and producing 360 lbs.-ft. of torque. Note in ’72, a “net” figure is used and not a “gross” measurement. The 350 LT-1 went on a 19-year hiatus but returned in 1991 as a small-block engine in the generation II.
1973 until 1980 the 350 L82
For the ’73 and ’74 models years, Chevy marketed the L82 as a performance 350 producing 250 hp (183.88 kW) with 285 lbs.-ft. of torque from the factory; this was an SAE net hp rating now. The 2.02 heads have a 76cc chamber size with the 624 casting number imprinted. The carburetor is the Rochester Quadra-jet four barrel bolted to the dual plane aluminum manifold, with the same hydraulic lifter cam as the earlier L46, and forged aluminum pistons with a 9:1 compression. The factory delivered these engines with crinkle black rocker covers with the distributor housing and the manifolds aluminum-colored. The Corvette in 1975 delivered 210 bhp (154.45 kW), but other models put out 205 bhp (150.78 kW) and developed 255 lbs.-ft. of torque. These figures remained the same through ’77, but in 1978, the Corvette L82 was slightly up and developed 220 bhp (161,8 kW) offering 260 lbs.-ft. of torque. For the ’79 model, the L82 350 engine 225 bhp (165.49 kW) for the last year, 1980, reached the high point of 230 bhp (169,17 kW). This same engine was also available for the Camaro.
The only year for the L81 version of the 350 was 1981 and was the only 5.7-liter engine in the Corvette for that year. The compression is 8.2:1 and with the high-performance cam working with the computer-controlled spark advance distributor, this version developed 190 bhp (139,73 kW) and produced 280 lbs.-ft. of torque. The “smart” carburetor made the L81 a one-of-a-kind. The Rochester Quadra-jet was altered to allow the fuel mixture to be controlled electronically; a sensor in the exhaust manifold feeds data to the Engine Control Module (ECM), altering the fuel/air mixture to meet demand. To be continued…