Big block vs. Small block

[BLKESC]

I know that big blocks make more hp & tq ( there's no replacement for displacement (outside of forced induction)), but where does the line for small blocks end and big blocks begin? Example: the largest small block Chevy made was the 400, but there was a 396 big block.

 

Thanks in advance for sheding light on the question.

[The SPEEDY]

Well I'm not the best for answering this question, but since nobody else has I'll give it a shot.

 

Small block and big block refers to the block that is used. Cubic inches has nothing to do with the name it is given. I think a 427 BB is a destroked 454, so a 396 BB must be a 427 crank with a smaller bore (probably why they are kinda rare). If I'm wrong someone will correct me.

 

No replacement for displacement. I love to force feed stuff.

[01Burb]

I'm also not an authority but own an old Chevy so I'll give it a bash:

 

The first modern big block chevy was the 396 of the mid 60s which appeared in Vettes and Chevelles and grew to 427 and then 454.

 

The small block dates back further to the mid 50s when it was (I think) a 265. That grew to the 327 of the early 60s (think Fuelly Vettes) and the 350 appeared in 67 in the Camaro.

 

Stroking a 350 can take you out to 383 - a popular size. I think the 400 was a Pontiac motor cus it was in the Firebird.

 

The fact that SBs and BBs overlap is simpy due to the mathematics of bore/stroke and displacement.

[02denali]

well it really depends on what you want.small blocks that are stroked can go as high as 490 cubes!!!!!. its basically what you are going after and how much money you want to spend. we run a 426 cubic inch small block stroked chevy. it runs great.11.26@129 in a 91 camaro. most peoples deal is the weight factor.then enter aluminum.basically it boils down to ---room---weight---horsepower---type of vehicle---money--money--money.

[americanmuscleman]

These guys posted some good info above.

 

The first GM big block was the 409. That was later replaced with the 396. That evolved into the 402 in 71' (but was still installed in the 396 SS cars). Derivations of the 396 were the 427 and 454. There are literally hundreds of different bore and stroke combinations you can come up with to have a big block go from as small as a 360ci to 700+ ci (tall deck blocks).

 

The first small block was a 265ci. The largest factory small block being a 400. Then there were all the sizes in between, 283, 302 (special 69' camaro motor), 305, 327, 350, etc...

 

The term big block and small block is used with respect to the overall size of the block. A big block and a small block are dimensionally quite a bit different. Like someone said above, its possible to have a high 4xx cubic inch small block, and a mid 3xx cubic inch big block.

 

[americanmuscleman]

There was the Pontiac 403. I forgot about that. I guess that takes the cheese for the largest factory GM small block.

[MarkD]

Small/Big block refers to the outer dimensions of the block. There are several "generations" of both big/small blocks GM's.

 

If you look at the valve cover of a small block (SB for short), it is about 5" wide (from intake manifold to headers). The valve cover on a Big Block (BB for short) is more like 8" wide. The distance between the valve covers is different also.

 

The biggest reason for choosing a SB over a BB is weight savings, room under the hood, and expense.

[2M3Bill]

Actually, there was a 366 big block truck engine. The Pontiac 403 was actually a smaller version of the big block 389, 421, 455.

[doverarjim]

Since I am an old guy I will throw my $0.02 in, a SB has the two center pistons closer together, if you look at the exhaust manifold or headers on a SB they will be right next to each other cylinders # 3,5 and 4,6 with #'s 1,7 and 2,8 being spread out from them. This is part of the cooling problems that SB have with all of the heat in these two cylinders. As for the valve covers the SB uses valves that go stright into the cylinder. The BB when first introduced with 396 ci was called a simihemi yeah like in Mopars, because the valves in the heads are canted(sp) that is the reason for the wide valve covers on BB the valves do not have the spark plug between them like a real hemi but it is off set from the valves. In 1961 Chev introduced the first gen BB it was the 348, and then came the most famous of all the 409 these were Big Blocks but they had troubles that were fixed when Chev redesigned the BB in 1964 and came out with the 396. Sorry about this being so long but the more I thought about it the more I wrote.

[BadBowtie]

Jim, the pistons of a 350 (or any SBC) are equally spaced, it is the valves that are close together. The 1 and 3and 5 and 7 intake are close together, so are the 3, 5 exhaust valves, but the exhaust valves for cyl 1, 7 are farther apart.

 

There are some pics here.