Chevrolet Chevelle 1970 SS 396 Convertible

Chevrolet’s fender badge said ‘396’ on every 1970 SS Chevelle, but the actual engine under the hood measured 402 cubic inches — a quiet update the automaker never bothered to advertise. Buyers chose between a 350-horsepower street engine and a 375-horsepower solid-lifter race motor, wrapped in a convertible body built in far smaller numbers than the hardtop. Clean examples now average around $105,000 at auction. Read on to find out why a mislabeled engine became one of the most valuable badges in muscle car history.

Chevrolet kept calling it the ‘396’ for an entire model year after the engine underneath that badge had already grown past that number — a bit of brand-equity sleight of hand that apparently nobody who ordered one in 1970 seemed to mind. What buyers actually got was 402 cubic inches of small-block-turned-big-block muscle, available in two distinct states of tune, wrapped in a convertible body Chevrolet built in far smaller numbers than the hardtop. So why does a car sold under a name that was already technically wrong keep climbing in value more than fifty years later?

A 396 That Wasn’t Actually a 396

Every SS 396 built in 1970 actually displaced 402 cubic inches — Chevrolet had quietly enlarged the bore the year before but kept the more recognizable ‘396’ name for marketing reasons rather than confuse a nameplate buyers already associated with performance. It’s a detail that catches plenty of modern shoppers off guard when they check a build sheet against the fender script and find the two numbers don’t match. Chevrolet’s own factory literature that year still referred to the engine informally as the ‘396’ in advertising copy even as internal engineering documents listed the true 402-cubic-inch displacement, an inconsistency that has confused buyers and restorers for decades.

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Two Engines Wearing One Badge

Buyers choosing an SS 396 in 1970 actually picked between two very different states of tune under that single 402-cubic-inch banner: the L34, rated at 350 horsepower for street use, and the solid-lifter L78 ‘Cowl Induction’ version rated at 375 horsepower for buyers who wanted something closer to a race motor with a factory warranty attached. The gap between them wasn’t cosmetic — it was the difference between a comfortable cruiser and a genuine strip-ready big block. Both versions used the same basic block and bore, but the L78’s mechanical lifters, higher compression, and more aggressive camshaft profile demanded more frequent valve adjustments in exchange for the extra 25 horsepower.

Muncie Four-Speeds and the Rock Crusher

Transmission choices ran from a base three-speed manual up through Muncie’s M20 and M21 four-speeds, with the heavy-duty M22 ‘Rock Crusher’ four-speed reserved specifically for the highest-performance engine and axle combinations. The Rock Crusher earned its nickname from the distinctive gear whine its straight-cut teeth produced at speed, a sound that instantly separated a serious L78 build from a more casual L34 cruiser at any stoplight. Chevrolet rated the four-speed M21 for closer highway gearing than the wide-ratio M20, letting buyers choose between stronger acceleration off the line or more relaxed cruising rpm on the open road.

From NHRA Strips to Sunday Cruises

The L78’s solid lifters and aggressive cam profile weren’t just a badge exercise — they made those Chevelles genuinely competitive on the strip, and L78-equipped cars became regulars in NHRA Super Stock and Stock Eliminator classes through the early 1970s. That same combination, wrapped in a comfortable convertible body with air conditioning and a tilt wheel, made an unusual case for a car that could win a class race and still handle a Sunday drive. Several regional NHRA divisions maintained active L78 Chevelle classes well into the early 1970s, giving Chevrolet a visible motorsports presence that the automaker’s marketing department leaned on heavily in period advertising.

The Convertible Nobody Ordered as Often

Chevrolet built 49,862 SS 396 Chevelles across all body styles in 1970, and the convertible was always the minority within that count — most buyers who wanted the L78’s straight-line credentials chose the lighter, stiffer hardtop instead. That relative scarcity is a big part of why surviving convertibles, especially documented four-speed cars, command such a premium over their coupe counterparts today. Coupe production numbers for the SS 396 ran considerably higher than the convertible’s share, reinforcing just how deliberately most 1970 buyers avoided the extra cost and lighter structure of the open-top body.

A $200 Premium That Kept Growing

A 1970 SS 396 convertible carried a $3,639 sticker versus $3,439 for the coupe — a roughly $200 premium at the time that has since multiplied many times over. Well-documented cars today, especially numbers-matching L78 four-speeds and convertibles, routinely sell for multiples of that original spread, with clean V8 Chevelle SS convertibles now averaging somewhere around $105,000 at auction. Auction houses now routinely list documented L78 four-speed convertibles as some of the strongest-performing Chevelle sales of any given season, reflecting just how much collector demand has concentrated on this specific combination.

Bucket Seats and a Power Top for a Race-Bred Motor

What made the SS 396 convertible unusual wasn’t just the engine — it paired serious drag-strip hardware with genuine comfort features rarely found on strip-focused cars of the era: bucket seats, a tilt steering wheel, factory air conditioning, and a power-operated convertible top. That combination of everyday livability and NHRA-class performance is part of why the model still reads as a complete package rather than a stripped-down race special. Options like power steering, power brakes, and a rear-window defroster were common additions on convertible orders specifically, since buyers paying the convertible premium tended to spec the car more fully than hardtop shoppers did.

Sport Suspension as Standard Equipment

Every SS 396 came with Chevrolet’s sport suspension package as part of the deal, tightening up a chassis that otherwise shared its bones with far tamer Chevelles in the lineup. That suspension tuning, paired with either engine option, is what let period road testers describe the SS 396 as a genuinely balanced muscle car rather than just a straight-line specialist wearing a badge. That factory-installed sport suspension included stiffer front and rear springs, larger front and rear stabilizer bars on some combinations, and quicker steering ratios than a standard Chevelle, giving the SS 396 genuinely different road manners rather than just a badge and a bigger engine.

Why the Premium Keeps Growing Decades Later

Fifty years on, the gap between a base Chevelle and an SS 396 convertible has only widened, driven by a shrinking pool of documented, numbers-matching survivors and a collector market that increasingly values open-top big-block cars above their hardtop counterparts. A badge that was technically inaccurate the day it left the factory has become one of the most trusted names in the entire muscle car hobby. Share your thoughts in the comments below. That growing gap between coupe and convertible values has made verified drop-top L78 cars a frequent target of fraudulent re-creations, pushing serious buyers toward independent documentation before any purchase.

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