6) L78 396/425HP
(4.094 X 3.76)
Its “daddy” was first seen at Daytona in 1963. Designed to make Chevrolets competitive on the NASCAR high banks, the “Mystery Motor 427” blistered the field in qualifying runs. During the race, minor things such as water pump failure forced all entries to the pits. But the cat was out of the bag. Over another year of engineering saw its external dimensions increase about 1 inch—to where none of the Mystery Motor internals were interchangeable. In February 1965, two Turbo Jet 396 “big-block” engines replaced the pair of 409s: RPO L35, a 325hp torque engine featuring high-velocity, oval-port heads and an 800-cfm Rochester Quadrajet carb; and RPO L78, a 425hp, ultra-high-performance engine featuring rectangle-port heads, 11.0:1 compression, and an aluminum high-rise intake manifold with 800-cfm Holley carb. Either engine could be ordered in any fullsize model. Production: L35 55,454. L78 1,838. The L78 also saw its way into 2,157 Corvettes for an extra cost of $292.70. In ’65, the 425hp 396 was the quickest and fastest RPO Chevrolet ever produced. But that wouldn’t last long.
7) L72 427/425HP
(4.250 X 3.76)
Designated RPO L72, it was offered in 1966 Corvettes and 1966, 1968, and 1969 fullsize passenger cars. Rated the same as the ’65 L78 396, it actually produced 450 hp and was advertised as such early in model year ’66. Then, due to owner insurance cost flap (and theoretical potential loss of sales), its rating was quickly reduced to 425. Since new, this engine has proven to be a winner on all fronts and is the basis for all other solid-lifter big-blocks offered through 1969. Total 1966 L72 passenger car sales were 1,856. Big car L72 sales in 1968 and 1969 were 568 and 546, respectively. These late-’60s cars were huge. Performance fans chose Chevelles, Novas, and Camaros instead.
8) 427/430HP L88
(4.250 X 3.76)
The 1967-’69 RPO L88 race engine was rated at only 430 hp for obvious reasons—the first of which was the given rpm-reading: a mere 5,200. Why tell the world your 12.5:1-compression, mega-cam, rectangle-port 427 actually snorts out over 550 hp at 7,400 rpm? It was only available from the factory in the Corvette, or over the parts counter. This engine put out so much power and heat that it was very difficult to keep cool on the street.
Actually, there was a factory center console plate on Vettes so equipped stating, “Not For Street Use.” As it was indeed a road-racing terror, L88 Corvette sales in 1967-1969 were 20, 80, and 116, respectively. The L88 solid-lifter camshaft was Chevy’s best sounding cam to date, and thousands were sold to owners of solid-lifter 396 Chevelles, Camaros, and Novas who sought a max-power setup with an awesome-sounding rough idle.
9) 427/430HP ZL1
(4.250 X 3.76)
Developed initially for the 1969 Camaro Super Stock competition, it was only available through “Central Office Production Order 9560.” A ZL1 Camaro was a legal, factory-built Super Stock/B drag car. With an aluminum 427 producing over 550 hp, Chevrolet Engineering execs originally thought the bottom-line cost would be very racer-affordable. But when the corporate bean-counters became involved, no cost breaks were given. The engine ($4,160) cost more than the base price of the V-8 Camaro ($2,727). With sales tax, license cost, and shipping, out-the- door was just over $7,000. The ZL1 engine internally was much like the iron-block 427 L88. But the ZL1 had open-chamber heads for better high-rpm power production, plus floating wrist pins and a few other minor updates. Original Camaro production: 69. All 69 ZL1 I.D. numbers went unknown until the early 1980s. All were then were published in Super Chevy via then editor and co-author Doug Marion— thanks to Chevy’s legendary Product Promotion Department guru, Vince Piggins. Depending on who you believe, there were definitely two, and perhaps three, ZL1 Corvettes built and sold to the public.
10) 454/450HP LS6
(4.250 X 4.00)
It was a one-year/one-model super engine (1970 Chevelle SS) with sales totaling 4,475. Thousands more short- and long-blocks were sold for many years afterwards. Try four-bolt main bearing caps, 11.0:1 compression ratio, special high-lift camshaft, huge rectangle-port heads, and an 800-cfm dual-inlet Holley carburetor on a flat, aluminum intake manifold. Most LS6s also had the extra-cost cowl-induction hood option for cooler incoming air. Some of the non-cowl-induction-hood LS6 cars had a factory or aftermarket aluminum high-rise intake manifold. Wise owners thought it was more of a power-producer than the cowl hood, and they were right. With this high-rise intake manifold, a set of tubular headers and a super-tune, LS6s produced over 500 hp and ran in the high 11s at over 115 mph—with slicks and 4.10- 4.56:1 gears. Not bad for a 4,000-plus-pound street car. Today, the 450hp ’70 LS6 is to many the granddaddy of all the big-inch crate engines GM offers. There wasn’t a street tire made in 1970 that could handle the torque and horsepower of an LS6. When the Holley carb’s secondaries began to open, the rear tires broke loose.