Information on Small Block Chevy Head Casting Numbers

by Rob Wagner
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under the hood image by Lucy Cherniak from

Chevy small-block engine head casting numbers identify the model year, horsepower range, valve and chamber size and the size of the intake and exhaust ports. The most common heads sought by engine builders are ones identified variously as the "Camel Back," "Double Hump" or "Humper" heads used on a range of passenger cars and performance vehicles.


The small-block engine was manufactured by General Motors for Chevrolet and other GM vehicles from 1955 to 2002. It featured the following cubic-inch displacements: 262, 265, 283, 302, 305, 307, 327 and 405. The Chevy 350, introduced in 1967, can still be purchased today as a replacement engine. More than 90 million small blocks have been produced.


The casting number is a six-, seven- or eight-digit number, depending on the model year and model of the vehicle, found stamped on the head. For example, the casting number 3743096 belongs to 327-cubic-inch V-8 engines on the 1962 to 1967 GMC pickup trucks. Casting number 330545 is found on 350-ci engines on 1973 GM vehicles with a chamber size of 76cc and valve size of 2.02/1.60 inches.

Camel Backs

The popular Camel Backs can still be found in wrecking yards specializing in American-made vehicles. These heads are easily identified by the last three digits of the casting number: 461, 462, 186, 291 and 492. The Camel Backs are often confused with the "fuelie" heads found on fuel-injected Corvettes, but measurements of the intake and exhaust ports will reveal the Camel Backs are installed in the carbureted 302, 327 and 350 engines.

Camel's Casting Numbers

Casting number 3767462 identifies Camel Back heads on 327 engines in 1962 to 1967 GM models. Number 3782461 is found on heads on the 1964 to 1967 models equipped with the 327. Number 3917291 can be found on the 302, 327 and 350 engines in 1967 to 1969 models. Number 3927186 is found in the 1969 and 1970 models with the 302 and 350. The 1970 models equipped with the 350 is stamped with 3991492.

350 Replacements

The casting numbers also can identify whether the 350 is a factory-installed GM engine or a GM Goodwrench replacement engine. Casting number 33417369 identifies a replacement, or crate, engine for 1990 and later vehicles that can be equipped with the 350. It also will have "Hecho en Mexico" (Made in Mexico) stamped on it.

Canadian Engines

GM's Ontario, Canada, plant-manufactured engines for some of its older-model pickups and for the Studebaker Corp., a South Bend, Indiana, automaker. Casting numbers 3731556 and 1816887 were used on the 1957 and 1963 Canadian-produced 283-ci GM trucks, respectively. Number 3884520 is stamped on 283 Chevy engines, which were also used in the Studebaker Lark passenger cars. Number 3884520 identified the 327 used in the 1962 to 1967 Chevys, the Studebaker Avanti and the independent Avanti II after Studebaker ceased production in 1967.

Inferior Heads

The heads on the 1976 through 1987 GM vehicles can be identified with casting number 462624 with an intake/exhaust port size of 1.94/1.50 inches. These heads are prone to crack.

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