2000 green hornet

I understand where the C6 Z06 for 2006 will have a "small block" 427 cubic inch engine. Were the early 427's from the 1960's big blocks? And what is the difference? Is there a cutoff limit where a certain size engine must be a "big" block?

_Nomad_

Yes

LS WON

65 had the 396 and was the first year of disc brakes.

shopdog

There's no "cutoff" per se. A big block is a big block because it has large *exterior* dimensions. The old big blocks were huge hunks of cast iron. Modern casting and manufacturing techniques have allowed the block to be the same exterior size as previous generation small blocks while at the same time allowing internal displacement to be as much as, and in some cases more than, the older big blocks.

Miaugi

Well said!

capevettes

The advantage of the new small blocks over the old big blocks is horsepower without the weight so the handling is not compromised. The old big blocks were torquemasters but a little too front heavy for precise handling even with the heavy duty sway bars and springs.

Sparky65

Mostly true - 1969 saw two Corvettes and 69 Camaros with all aluminum 427's (ZL1) which were conservitively rated at 430 HP @ 5600 RPM and actually made over 560 HP at 6800 RPM - that was with a carburetor! It was also the beginning of the Can Am 430/465/495 aluminum block BBC engines, all in a package that weighed less than the small block 350 of the day. They all started life with a 4.44" bore and the strokes were 3.47"/3.76"/4.00" respectively. The main reason for the Big block design was the need to increase the bore spacing to accomodate larger bores/displacements. The heads with their canted valves also had the ability to feed the larger displacements and typically flowed much better. Aftermarket big blocks are available in both cast iron and aluminum from several manufacturers (World Castings, Brodix and Donovan to name a few) with bores up to 4.600" and stroke capacity in the 4.75" range (that's 632 cubic inches!) and others are available in the 700-800 cubic inch range. The list goes on but the main reason was cubic inches.

Duck916

You mention future C6 engines in your title. The LS-7 pretty much represents the maximum displacement you can get out of an LSx block--there's not much room for more bore or stroke. Additionally, given the current status of the world markets, I doubt you'll ever see a bigger production engine in any future Corvettes. Maybe more power someday, but I think this 427 is going to be as big as it gets going forward.

mforman42

All of the above are correct. Traditionally, the bore spacing has remained constant for each line, and this has simplified the manufacturing process. In the old iron block days, small blocks were:

265, 283, 302, 305, 307, 327, 350, 400 cubic inches

Big blocks were: 396, 402, 427, 454 cubic inches

Note that swapping various cranks into various bore blocks can yield interesting combinations, as well. The 302 was basically a 283 crank throw in a 327 block bore.

Ford with the 221/260/289/302/351 line small blocks and 332/352/390/406/427/460 big blocks and Mopar 273/318 small block and 360/383/426/440 big block were similar.

LS WON