1968–1970 Chevrolet Chevelle SS 396: Specs, History

1968–1970 Chevrolet Chevelle SS 396 (2nd Gen): The Big‑Block A‑Body Benchmark

Historical context and development background

When Chevrolet’s mid-size Chevelle entered its second generation for 1968, it did so with a new “Coke-bottle” profile, a stiffer perimeter frame, and a mandate to outmuscle Pontiac’s GTO, Oldsmobile’s 4-4-2, Buick’s GS, and Mopar’s Road Runner/GTX. Within that family, the SS 396 was the sharp end of the spear. In 1968 the SS 396 was a distinct series (VIN beginning with 138), offered as a Sport Coupe and Convertible. For 1969, Chevrolet recast SS 396 as Regular Production Option Z25 on the Malibu, broadening its appeal; the theme continued for 1970, when the big-block grew to 402 cubic inches but—true to Chevy marketing—it kept the familiar “396” badging.

Corporate context mattered. GM’s A-body platform underpinned Chevrolet, Pontiac, Oldsmobile, and Buick intermediates, so the Chevelle’s hardware had to be competitive inside and outside the corporation. Chevrolet’s solution blended a torquey Mark IV big-block with pragmatic chassis tuning: unequal‑length double A‑arms up front, a four‑link coil‑spring rear, and (on many SS cars) the heavy‑duty F41 package with a rear anti‑roll bar and boxed lower rear control arms. Disc brakes and a factory cowl‑induction hood (RPO ZL2) joined the order sheet by 1969, sharpening the SS narrative from boulevard bruiser to legitimate quarter‑mile threat.

Motorsport presence skewed to the drag strip. In NHRA Super Stock and Stock Eliminator, L78 solid‑lifter SS 396s became fixtures, their consistency and torque making them competitive class cars. While Chevrolet’s road‑race and NASCAR energies centered on Camaro and later Monte Carlo, the Chevelle SS 396 carved its reputation launching hard between the lights.

Engine and technical specifications

Across 1968–1970, the SS 396 name encompassed three primary big‑block tunes. The engines shared deep-skirt Mark IV architecture, 4.094‑inch bore and 3.76‑inch stroke, a forged crank (on high-performance builds) and robust bottom end reliability. In 1970, a minor overbore pushed displacement to 402 cu in; Chevrolet retained “396” emblems for brand equity.

Transmissions ranged from a standard 3‑speed manual to the Muncie M20/M21 4‑speeds, with the heavy‑duty M22 “Rock Crusher” appearing in specific high‑performance axle/engine combinations. The Turbo‑Hydra‑Matic 400 3‑speed automatic was the big‑block automatic of choice. Most SS 396 cars used a 12‑bolt rear axle with ratios from highway‑friendly 3.31 to drag‑strip 4.10 and steeper.

Driving experience and handling dynamics

A good SS 396 feels unfiltered and mechanical. The Mark IV big‑block’s defining trait is torque—an instant swell from idle that makes even the mild L35 move the Chevelle’s mass with authority. Hydraulic‑lifter L35/L34 engines respond crisply with a broad, streetable torque curve; the L78, with its solid lifters and lumpier cam, likes a decisive right foot and rewards it with a harder charge above 4,000 rpm. Throttle response improves materially with the optional cowl‑induction hood, which ducted high‑pressure air from the base of the windshield to the air cleaner via a vacuum‑operated flap.

Steering is recirculating‑ball—durable and honest rather than delicate. The best‑sorted cars wear the heavy‑duty F41 pieces, which add a rear anti‑roll bar and boxed lower control arms to tame axle wind‑up and reduce roll. The ride is firm by period standards but never brittle; the Chevelle communicates weight transfer and mid‑corner grip through the seat, not just the wheel. Braking is competent with front discs and rear drums; fade resistance is adequate for brisk road work and much improved over all‑drum setups.

The manual gearboxes give the car its most involving personality. A correctly set‑up Muncie snicks between gates with a satisfying mechanical clack, and an L78 on an M22 with short rear gears is every bit the visceral muscle‑era archetype. TH400 automatics are stout and well‑matched to the big‑block’s torque, particularly for cars that spend time in traffic or at the strip.

Performance specifications

Period instrumented tests varied with axle ratio, transmission, and options. The figures below reflect representative results owners and magazines recorded for stock SS 396s.

Variant breakdown (1968–1970)

Key visual differences include SS‑specific badging and trim, simulated hood vents (1968), available cowl‑induction hood (1969–1970), stripe packages, and 14‑ or 15‑inch rally wheels. Beyond cosmetics, the shift from a standalone SS series (1968) to an option package (1969–1970) is the most consequential delineation.

Notes: Chevrolet’s official records for option‑package totals and body‑style splits (especially 1969–1970) are incomplete. The figures above reflect widely cited totals from period documentation and enthusiast registries; they should be treated as informed estimates rather than audited counts.

Ownership notes: maintenance and restoration

• Engine care: Big‑block Mark IVs are durable when kept cool and fed quality oil. Expect frequent valve‑lash checks on L78 solid‑lifter engines; many owners set lash every few thousand miles. Hydraulic‑lifter L35/L34s are notably low‑maintenance.
• Cooling and fuel: Factory radiators are adequate if clean; many cars benefit from re‑cored units and proper shrouding. The original high compression ratios were tuned for high‑octane leaded fuel; detonation control via timing and octane selection is part of modern ownership.
• Driveline: The Muncie M20/M21 and TH400 are stout; clutch chatter is commonly traced to worn engine/trans mounts or clutch linkage geometry. The 12‑bolt rear axle is robust; listen for carrier whine and check axle seals.
• Chassis and rust watch‑points: A‑body frames can scale at the rear kick‑ups and around body mounts; inspect cowl plenum, rear window channels, lower fenders, and floor pans. Boxed lower rear control arms (F41) resist twist; many non‑F41 cars have been upgraded.
• Parts availability: Excellent. Reproduction sheetmetal, interior trim, and correct date‑coded components are widely available. Original‑type Holley and Quadrajet carburetors, smog equipment, and cowl‑induction pieces carry premiums.
• Service intervals: Period practice was 3,000‑mile oil changes; tune‑ups on points ignition every 10,000–12,000 miles are typical. Solid‑lifter lash intervals as noted above.
• Restoration difficulty: Mechanically straightforward; the challenge is provenance. Matching‑numbers engine, transmission, 12‑bolt, and documentation (build sheets often turn up on top of the fuel tank) materially affect value.

Cultural relevance and market standing

The Chevelle SS 396 is one of the canonical muscle cars: an accessible, handsome coupe with authentic big‑block punch. It was a constant presence in late‑1960s enthusiast magazines and a regular sight at local drag strips. Popular culture has often leaned on Chevelle SS imagery to telegraph American V8 bravado, and while the 454‑badged 1970 cars often steal the limelight, well‑documented SS 396s—especially L78 4‑speeds and convertibles—are blue‑chip collectibles.

Auction and private‑sale results have consistently rewarded correctness: cars retaining original drivetrains, colors, and rare options (cowl‑induction, F41, gauges/tach, tilt, special‑order axle ratios) command significant premiums. As always, documentation is the dividing line between simply nice and truly investment‑grade.

FAQs

Is the 1970 SS “396” actually a 402?
Yes. For 1970, Chevrolet enlarged the bore slightly, taking displacement to 402 cu in, but retained “396” badging for continuity.

Which SS 396 engine is most desirable?
The solid‑lifter L78 (375 hp) sits at the top of the SS 396 hierarchy due to performance and relative scarcity. Among hydraulic‑lifter engines, the L34 (350 hp) offers a nice blend of drivability and pace.

How quick is a stock SS 396?
Expect roughly 0–60 mph in the 6–7 second range and quarter‑miles in the mid‑14s for L34 cars, with L78s dipping into high‑13s when well‑driven and properly geared.

What gearboxes were available?
Standard 3‑speed manual, optional Muncie 4‑speeds (M20/M21, with M22 in specific high‑performance combinations), and the Turbo‑Hydra‑Matic 400 automatic.

Common issues to inspect before buying?
Cooling system condition, evidence of detonation on high‑compression engines, frame rust near rear kick‑ups/body mounts, correctness of SS‑specific components (dash, gauges, steering box ratio, 12‑bolt axle), and documentation proving it’s a real SS (especially 1969–1970 option‑package cars).

How does the SS 396 compare with period rivals?
Against a GTO 400, 4‑4‑2 400/455, GS 400/455, or Road Runner 383, the SS 396’s torque, gearing breadth, and parts availability make it a sweet spot—fast, durable, and straightforward to own.

Were COPO 427 Chevelles “SS” cars?
No. COPO 427 Chevelles (notably 1969 L72 cars) typically lacked SS badging; they were special‑order big‑blocks built outside the regular SS program.