Camaro Z28 RS DZ302 1969

Chevrolet built the 1969 Camaro Z/28’s 302 small-block by splicing together parts from two completely different engines, all to sneak under a racing rulebook’s displacement limit. The factory horsepower rating on the DZ 302 was famously conservative — real output ran closer to 400 horsepower than the advertised 290. That combination of underrated power and homologation-special engineering helped the Z/28 win back-to-back Trans-Am championships. Here’s how Chevrolet built one of its most respected small-blocks ever.

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Chevrolet built the 1969 Camaro Z/28 to homologate a race engine for SCCA competition, and the result was one of the strangest specification sheets in muscle car history — a small-block rated well below what it was actually capable of, wearing a factory horsepower number that nobody who drove one ever quite believed. Under the hood was an engine built from mismatched parts pulled from two completely different Chevy V-8s, engineered specifically to squeeze under a rulebook limit rather than to look good on a window sticker. The result won back-to-back championships and became one of the most respected small-blocks Chevrolet ever built. What was Chevrolet actually hiding behind that conservative rating?

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A 302 Built From Two Different Engines

The DZ-code 302 was not a clean-sheet design — Chevrolet built it by combining the block from the 327 with the shorter-stroke crankshaft out of the 283, landing at exactly 302.4 cubic inches. That specific displacement was not an accident: SCCA Trans-Am rules capped engines at 305 cubic inches, and Chevrolet needed something under that ceiling that could still turn serious RPM. The DZ 302 got forged pistons, a forged steel crank and rods, a solid-lifter cam, and an 11.0:1 compression ratio, fed through a 780-cfm Holley four-barrel on a dual-plane intake.

290 Horsepower on Paper, Closer to 400 in Reality

Chevrolet officially rated the DZ 302 at 290 horsepower at 5,800 rpm, a number widely understood at the time — and confirmed by later dyno testing — to be deliberately conservative, with real output closer to 400 horsepower. That sandbagged rating helped keep insurance costs and factory liability down while still delivering a screaming, high-revving engine built to be driven near redline. Roughly 20,300 Z/28s were built with the 302 and a Muncie four-speed, running the quarter-mile in the mid-14s.

A Trans-Am Championship Engine for the Street

On track, the 302-powered Z/28 delivered exactly what it was built for: back-to-back SCCA Trans-Am Manufacturer’s Championships in 1968 and 1969, going wheel-to-wheel with Ford‘s Boss 302 Mustangs on road courses across the country. That racing pedigree is a big part of why the RS/Z28 package remains one of the most collectible first-generation Camaros today — it is a genuine homologation special that happened to also be sold to the public, wearing rally stripes and cowl induction instead of a windshield net and roll cage.

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