Chevrolet’s DZ 302 cubic-inch powerplant is regarded as one of the most legendary small-blocks that Chevrolet ever developed. With its unique design and rich history — both in road racing and on the strip, it has definitely earned its respect.
The 302 cubic-inch engine was developed as the powerplant for the first-generation Z/28 Camaro (model years 1967 through 1969). It utilized the block from a 327 cubic-inch engine, and a crankshaft from a 283 cubic-inch engine, resulting in a 302.4 cubic-inch displacement. This placed the engine under the SCCA Trans-Am limit of 305 cubic inches, allowing it to serve its primary purpose of rivaling the Mustang of the day.
It did more than just rival it, however. The 302 ci-powered Z/28 performed extremely well in both NHRA drag racing and the SCCA Trans-Am series. In the latter, it claimed the 1968 and 1969 Manufacturer’s Championship titles back-to-back. Doing so fulfilled developer Vince Piggins’ vision of the car being superior to the Mustang, and also marked the origin of both the Z/28 and the 302 cubic-inch engine’s legacies.
Aside from its heritage, what really made the 302 cubic-inch engine special was how unique it was. The engine was given an oversquare design, created by the 4.00-inch bore and 3.00-inch stroke. The large bore coupled with the short stroke allowed the engine to rev well into the 7,000 rpm range. This type of small-displacement, high-revving platform was a bit radical in an age of big-block, 5,500 to 6,000 rpm-limited engines. However, the small-block’s design allows it to have high-horsepower potential and incredible reliability, as opposed to its larger, lower-revving counterparts.
To handle the high engine RPM, the 302 cubic-inch V8 was equipped with a forged-steel crankshaft and connecting rods. The pistons were also forged, to handle the 11.0:1 compression ratio. The cylinder heads featured large ports and valves (2.02-inch intake, 1.60-inch exhaust) to aid with air flow at high engine RPM, but did so at the cost of decreased performance in low and mid-RPM ranges.
To complement the other high-performance aspects of the engine, the 302 cubic-inch engine was fitted from the factory with a single 780-cfm Holley four-barrel carburetor and a dual-plane high-rise intake manifold. This was stock equipment for all three years of production, but in 1969, buyers could opt for an aluminum, dual four-barrel cross-ram intake with two 585-cfm Holley carburetors.
In 1967, all 302 cubic-inch engines — except those manufactured in Van Nuys, California, used the same carburetor. This difference was due to California emissions regulations, which required that vehicles sold in California use an AIR (air injection reaction system). However, the 1968 and 1969 302 cubic-inch engines were all equipped with an AIR emissions system, meaning all 302 cubic-inch engines of those years received the same carburetor.
In the modern day, the Chevy 302 cubic-inch engine is a much-sought after piece of muscle car history. Few engines of the time were capable of producing such great power from such a small a displacement, or boasting such a high a level of reliability. Though not the largest or most powerful engine that Chevy has ever produced, the 302 cubic-inch V8 is definitely one of the most distinguished.