How much horsepower does a 1967 Impala SS 427 have?

[VonAngela]

The 1967 Chevrolet Impala SS 427 was available with two distinct 427 cubic-inch big-block V8 engines, offering 385 horsepower and 425 horsepower respectively. The lower-output version was the L36 Turbo-Jet, while the high-performance option was the L72. These figures are well-documented in factory specifications and authoritative automotive archives like the National Corvette Museum SPC sheets and GM Heritage Center records.

The horsepower difference stemmed from crucial engineering choices. The 385-hp L36 engine used a milder camshaft and a single 4-barrel carburetor, designed for strong street performance with smoother driveability. In contrast, the 425-hp L72 engine was built for maximum output, featuring a more aggressive camshaft profile, solid lifters, and a high-rise aluminum intake manifold paired with a larger 4-barrel carburetor. This configuration required premium fuel but delivered race-ready power.

A concise comparison of the two engines clarifies the spec differences:

Engine RPO Code	Horsepower (SAE Gross)	Torque (lb-ft)	Compression Ratio	Key Feature
L36	385 hp	460 lb-ft	10.25:1	Single 4-bbl carb, hydraulic lifters
L72	425 hp	460 lb-ft	11.0:1	Aluminum intake, solid lifters

Regarding transmission pairing, the original answer contains a common inaccuracy. The three-speed Turbo Hydra-Matic was not available on the Impala SS 427. Factory documentation shows that both the L36 and L72 engines were exclusively paired with a heavy-duty 3-speed manual transmission as standard. A 4-speed manual was a popular option. The two-speed Powerglide and three-speed Turbo Hydra-Matic were only offered with smaller-displacement engines that year.

Identifying which engine a car originally had is straightforward. The L72 engine with its aluminum high-rise intake manifold is visually distinctive. The most definitive method is to check the vehicle's trim tag or protect-o-plate for the engine RPO code (L36 or L72) or to locate the engine's partial VIN stamp. In today's collector market, cars documented with the original 425-hp L72 engine command a significant value premium, often 30-50% more than a 385-hp model, due to their rarity and high-performance pedigree.

[AuroraDella]

As a mechanic who’s worked on a few of these, the 425-horsepower L72 is the one that gets your attention. You pop the hood and that big aluminum intake manifold tells you everything. It’s a race-bred engine. The solid lifters mean you need to adjust the valves, and it wants premium fuel. The 385-hp version is much tamer for daily driving—still a torque monster, just easier to live with. And forget about an automatic behind these 427s; they all came with a stout 3-speed manual from the factory.

[McSavannah]

I’ve owned my '67 SS 427 for twenty years, and its power never gets old. It has the L36, so it’s rated at 385 horsepower. That’s more than enough for thrilling acceleration and a deep, rumbling exhaust note that defines the American muscle car era. When I was looking to buy, I learned the hard way about verification. I checked the stamp pad on the engine block to confirm the numbers matched the car's paperwork. Many cars have had engine swaps over the decades. For a true collector, that factory-original match is what determines both authenticity and the car’s market value. The 425-hp cars are spectacular, but they’re also far more expensive to buy and maintain.

[Cheyenne]

Let’s clear up the transmission myth. If someone tells you their 1967 Impala SS 427 left the factory with a Turbo Hydra-Matic, the facts don’t support it. Historical order guides and build sheets confirm Chevrolet paired the big 427s only with manual gearboxes. The Turbo Hydra-Matic was available, but only for smaller V8s like the 327. This is a key detail for authenticating a true SS 427. The standard was a rugged 3-speed manual, with a 4-speed as a common option for enthusiasts who wanted closer gear ratios.

[LeLucia]

From a market valuation perspective, the horsepower rating is the primary driver of value for a 1967 Impala SS 427. Hagerty and other insurer valuation tools treat the 425-hp L72 and the 385-hp L36 as entirely different models. An authentic, documented L72 can reach auction prices well into the six-figure range, reflecting its status as a pure performance icon. The L36, while still highly desirable, trades at a more accessible level. For any serious buyer, the due diligence process is non-negotiable: you must verify the engine code and stampings against the VIN. Originality is everything. Restorations that correctly match the engine to the car’s born-with specs preserve this value, while incorrect engine swaps diminish it considerably.