The L78 396: The Big-Block SS Brute

What separated the L78 from other 396 options

Chevrolet offered the 396 in multiple states of tune for the Camaro SS. The base big-block was the L35, rated at 325 horsepower, followed by the L34 at 350 horsepower, which arrived for 1968. The L78 sat at the top of the regular production 396 hierarchy at 375 horsepower. The differences between these engines were not cosmetic. Each step up the ladder brought meaningful mechanical changes.

The L78 used a solid-lifter camshaft, where the L35 and L34 used hydraulic units. Solid lifters allowed the L78 to rev more freely and maintain valve timing accuracy at higher engine speeds, though they required periodic lash adjustments. The L78 also featured closed-chamber cylinder heads with larger-diameter valves than the lower-rated versions, and a higher compression ratio of 11.0:1 compared to the L34's 10.25:1. These are not minor details. They represent a fundamentally different approach to how the engine makes power.

For drivers who wanted torque with less mechanical fussiness, the L34 was arguably a better street choice. But buyers who ordered the L78 were making a statement about priorities: maximum output, regardless of the maintenance demands. The complete Camaro performance picture shows how SS big-block buyers compared to Z/28 buyers in terms of intended use and driving character.

Inside the L78: hardware details

The 396 block itself was a robust casting, part of the Mark IV big-block family that Chevrolet introduced in 1965. The block shared architecture with the 427 used in COPO applications, which meant that the bottom end was engineered with significant strength margins. The COPO Camaro piece explains the relationship between the 396 and 427 families in more detail.

The SS package and what it added beyond the engine

The L78 was an engine option ordered on top of the SS (Super Sport) package, which was itself an appearance and performance group. RPO Z27, the SS package, included SS badging, a specific hood with non-functional air inlets, special striping, and upgraded suspension compared to the base Camaro. The 396 engines, the L78 among them, were options added to it.

Pairing the L78 with the M22 "Rock Crusher" four-speed manual gearbox and a steep rear axle ratio produced a car that was frankly difficult to drive on public roads at legal speeds. The combination was optimized for the drag strip, where the L78's torque could be deployed in short, controlled bursts.

Understanding how the SS, RS, and Z/28 packages differed is essential context. The RS vs SS vs Z/28 comparison lays out exactly what each badge meant and which options could be combined.

Recognizing an L78 in the field

Engine suffix codes stamped on the block pad identify the engine option. For the L78 in a 1967 Camaro, the manual-transmission suffix codes are "MQ" and "MR" (the latter with the K19 air-injection smog equipment). The codes changed slightly year to year, so a Camaro-specific code reference guide is essential for verification work. Do not rely on memory or general knowledge for suffix codes, as the same engine in a different application carried a different stamp.

Verifying that all the identifying numbers match across the VIN, trim tag, block pad, and available documentation is the harder part. across the VIN, trim tag, block pad, and available documentation.

"The L78 does not need to rev to make you pay attention. It makes itself known from about 2,500 rpm and just keeps pulling. That torque is what the SS buyer was after, not a redline. You feel it through the seat."

Mike Sullivan

Next up in this performance silo: what the RS, SS, and Z/28 badges actually meant and how they could be combined on a single car.

Sources and notes

Production figures, engine specifications, codes, and dates in this article are cross-referenced from established Camaro references, period documentation, and owner registries. Where sources differ, the most commonly cited value is used. Cost figures are indicative and vary by supplier, region, and condition.

• 1967-69 Camaro Drivetrain Decoding - CRG
• Chevy 396 & 402 Big Block Guide - Complete Specs - Muscle Car Club
• Chevrolet L78 - Grokipedia
• 1968 Chevrolet Camaro Fact Sheet - Over-Drive Magazine
• 1967-1981 Camaro Engine Guide - SS396.com

Updated November 3, 2026: Corrected: the L78 was the most powerful 396 in the Camaro SS (not every Camaro), the L34 arrived for 1968, and the SS package contents were restated. Claims about valve covers, a 4.10 axle pairing and later stroker builds were removed.