Engine Block Casting Numbers - Big Block

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Big block V8: 348, 366, 396, 409, 427, 454 - Small block here

>> Page #1: 340220 to 3963276

>> Page #2: 3963512 to 14015445

For purposes of this reference the 348 and 409 "W" engines are considered big block engines since these are larger and longer than the small block. First introduced in 1958 with 250hp or 315hp with a 4-barrel carburetor and 280hp with 3x2-barrel carburetors. The 348 lent itself to very nicely to dress-up items such as polished valve covers and individual air cleaners on the 3x2 setup.

The 348 continued until the 1961 model year ultimately with 350hp on tap. Late in 1961 the bore and stroke were increased to produce the iconic 409. The 409 continued through early 1965 when it was dropped in favor of the newer design 396 engine. During the 409's heyday it ranged from 360hp to 425hp in 4-barrel and 2x4-barrel versions. Who can ever forget the "She's real fine my 409" by the Beach Boys of the 60s?

Midway into the 1965 model year the 409 was replaced with the 396cid engine, affectionately dubbed the "rat motor."  The 396 engine came in a 2-barrel version available in passenger cars and a 4-barrel version that would be offered, eventually in every Chevrolet lineup. The 4-barrel version of the 396 came in three basic horsepower ratings from 1965 through 1970, 325hp, 350hp, and 375hp. The 396 eventually grew to 402 cubic inches in 1970 but the SS optioned Chevelles and Novas continued to use the "396" nameplate as GM had invested a lot of expense in the SS396 nameplate mystique. In 1970 a second version of the 402 was offered in any non SS optioned Chevrolet and was oddly enough marketed as a Turbo-Jet 400, available under RPO LS3.

When GM lifted the self-imposed ban on engine size in 1970, the 396 grew to 454 cubic inches initially offered in 360hp and 450hp versions. The 450hp RPO LS6 engine was the highest factory horsepower rating of the big 3 automakers at the time. A third version of the new Mark IV big block was the 427 cubic inch engine introduced in 1966 in full size Chevrolets and Corvettes. Except for a short run of special order COPO Chevelles and Camaros in 1969 the 427 was not available in any other make in the Chevrolet lineup.

Crate engines, or more specifically engines that would be built and sold through GM and aftermarket distributors, began to appear in the late 70s for those enthusiasts wanting more cubic inches and more power. The General Motors 502 cubic inch engine fit the bill for the rat motor crowd. With a whopping 461 horsepower and 558 lb.-ft. of torque the 502 HO engine was offered. If the 502 HO crate engine was not enough, Chevrolet released a 572 cubic inch monster in two versions, 621hp and 645 lb.-ft. of torque and 727hp and 680 lb.-ft. of torque

1970 SS396/SS454 Atlanta/Baltimore/Kansas City/Van Nuys Build Sheet Decoder

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