Difference between a big block and a small block

Thanks for all the interesting replies. Thorp31 gave me an idea on how to explain the difference.

Son, since the 1950's, several automobile manufacturers such as Chevrolet, Ford, Chrysler produced V8 engines that some people labeled as small blocks and big blocks. Chevrolet had its own small block line of engines that shared the same bore spacing of 4.40" for the 265, 283, 302, 307, 327, 350, 400. Chevrolet also had its own big block line of engines that shared the same bore spacing of 4.84" for the 348, 396, 402, 427, 454. The two different bore spacings determined whether an engine is a big block or small block

In much the same way of thinking, this later got carried over to the Ford and Chrysler engine line up by the general public. Ford had its own line of small blocks engines that shared the same bore spacing of 4.38" for the 260, 289, 302,351, 400. Ford also had its own big block engines that shared the same bore spacing of 4.63" for the 352, 390, 427, 428.

And, it was similar for the Chrysler engine line up with all the small blocks having a bore spacing of 4.46" for the 273, 318, 340, 360. Chrysler had big blocks with a bore spacing of 4.5625" for the 301, 331, 354, 392, Also, Chrysler had a big block line up with the bore spacing of 4.8" for the 350, 361, 383, 400, 413, 426, and 440.

So we can surmise that bore spacing had more to do with whether an engine is a big block or a small block.

He loves to play devil's advocate. I'll present him with the aforementioned and some of the posts for clarification, this weekend. Thanks again for all your input.

 

I vote for weight

 

In 1970 Chevy came out with the 400 sb and the 402 bb. The 400 small block and the 402 big block are the same bore and stroke and are the best to compare. The deck height on the bb is taller, rods are longer, valve and port size is bigger, and the rocker ratio on the bb is 1.7 compared to the sb 1.5. The 402 p***enger car engine will make more torque and hp every time.

The only thing the bb engines have going against them is there's a limit to the rpm's. They have larger bearings which increases surface speed on the bearings limiting rpms. The larger stems and valve heads (2.08-1.72 bb 2.02-1.6 sb)increase weight in the valvetrain, magnified by the higher rocker ratio limits rpms. Weight of the rotating ***embly is also a hurdle, but it's acceptable because of the increase in durability.

The best street engine I ever had was a 400 sb with the biggest heads I had ported to the max(2.05 1.6), a mild cam (comp 280h with 1.6 rockers .500 lift) and 10 to 1 compresion. I just tried to make my sb a bb.....

 

Good simple illustration.
Thanks,
Cheers..........