Lot 433: 1970 Chevrolet Chevelle SS 454 LS6 Two-Door Hardtop

There was a time, which some collectors are old enough to remember, when each GM division designed, developed and oversaw the building of its own engines. It seems almost inconceivable these days when platform- and drivetrain-sharing are the mantra of successful, cost-saving auto companies. In the days after World War II, though, as overhead valve V-8 engines quickly supplanted inline eights, sixes and even fours each marque followed different design and development paths.

The practice was much less common at Ford and Chrysler which shared design concepts and engines among marques. At GM, however, with over 50% of the U.S. auto market, giving the engine designers at Chevrolet, Pontiac, Oldsmobile, Buick and Cadillac a free hand to express their ideas in cast iron, steel and aluminum gave GM the opportunity to evaluate many different concepts in the diverse environment of the real world.

One of the most successful of these development paths started at Chevrolet in 1958 when the W-series big block engines were introduced with 348 cubic inches. Interestingly the W-series was originally conceived and designed for use in Chevrolet’s mid-sized and large trucks. It incorporated a very unusual design, with the block deck machined at a 74-degree angle instead of perpendicular to the bore axis. The heads that mated to this angled deck were essentially flat with the combustion chamber formed entirely within the cylinder. It was expected to deliver unusually good breathing at low and mid-range crankshaft speeds and exceptional mid-range torque – perfect for trucks but not especially suited to the needs of high performance automobiles.

For at least a few years the shortcomings of the W-series at high rpm were masked by its positive attributes and increases in displacement from 348 cubic inches to 409 and eventually to 427 but soon it became apparent that the burgeoning high performance market dictated a replacement better suited to making high rpm horses. It made its appearance in 1963 at the Daytona 500 where the ‘mystery motor’ cleaned up in qualifying. It then disappeared for more development before appearing as the Mark IV at 396 cubic inches in 1965.

The Mark IV was a development of the W-series, sharing many of the design elements that had proven themselves in that engine. The main difference was that the Mark IV utilized more conventional cylinder heads and a 90-degree deck. The valves were staggered and, exploiting the design flexibility of Chevy’s stud-mounted stamped rocker arms, their stems were canted in both planes earning the Mark IV the ‘Porcupine’ nickname. Built for strength, the Mark IV weighed a little more than its predecessor. It made lots more power to make up for the extra pounds.

Only a year after the Mark IV was introduced it grew in size to a full seven liters, 427 cubic inches. The final adjustments in engine size came in 1970 when the smaller engine increased from 396 to 402 cubic inches (still called a ‘396’ for marketing reasons) and the biggest big block grew to 454 cubic inches. With a 4 1/4” bore and 4” stroke the 454 cubic inch Mark IV combined superb breathing with abundant cubic inches.

It was a smashing success, so much so that a few years later the Mark IV was adopted by GM as the big block engine used across the board in all its marques. The ultimate Mark IV, introduced simultaneously with the increase of 454 cubic inches, is the LS6.

Rated at 450 horsepower the times turned in by showroom stock LS6s indicate that each engine was making over 500 horsepower. It had four-bolt main bearings, big port, big valve heads, solid lifter cam and a low-rise aluminum intake manifold with a giant Holley four-barrel. Given a place between the front wheel wells of a Chevelle SS the LS6 454 was the king of muscle cars.

The 1970 Chevrolet Chevelle SS 454 LS6 two-door hardtop offered here is a simply stunning example that is mostly original and in outstanding condition for its age. The original Protect-O-Plate and two separate build sheets authenticate its equipment. A copy of the window sticker, the original Owner’s Manual and a copy of the original dealer invoice are included in the package.

Finished in Black with a matching Black interior, in addition to the 454/450hp LS6 engine it is equipped with a Muncie four-speed manual transmission, power front disc brakes and bucket seats. It has its original smog equipment installed. The interior has no console and only a simple pushbutton radio. There has been at least one repaint; the engine has been out of the car and repainted; the chassis is clean and original and has apparently never had any undercoating.

This is an exceptionally fine, largely unmolested, honest Chevelle SS 454 LS6 two-door hardtop that should be the centerpiece of any muscle car collection fortunate enough to contain it.

Without reserve