Are there any hard and fast visual clues to identify a big block from a small block at a glance?

[Snattlerake]

I heard the exhaust outlet placement on the heads was a pretty good indicator of the differences.

EX:

Small block

The two middle exhaust ports are closer together than a big block


Big block

My question, is this standard accross the board for all small blocks and big blocks?

 

[red442joe]

Size?

Joe

 

[JH47]

Are you talking Chevy engines only or across all brands?
The fan shroud is usually a give away as it is much smaller on a Big block since the engine sits closer to the radiator.
The valve covers are the first thing I look for since the Big Block covers are much wider.

 

[red442joe]

With regard to Oldsmobile V8's, big blocks have a raised ridge with a stiffening rib across the top of the timing cover. All the heads are the same size, but the big block intake is MUCH wider.
Chevy big blocks have a wide, flat, squared oval valve cover, quite different, and larger than small blocks.
Small blocks have siamesed center exhaust ports, though there are aftermarket even spaced port heads.

Joe

 

[Dumpstick]

Mopar v8 small blocks had the distributor in the back, sticking straight up.
,Big blocks the distributor was in the front at an angle. Kinda laying over to the passenger side.

 

[Shadowrider]

The valve covers are the first thing I look for since the Big Block covers are much wider.

Yep. Also, Chevy BB valve covers have more bolts too. There isn't any mixing them up.

 

[swampratt]

^^^ yes valve covers are a dead giveaway and .0005 seconds to tell Big block chevy from Small block chevy.

Big block valve cover.

And here is a SBC cover.

Notice the Small block has minimal holes just 4.

On Oldsmobile I knew casting numbers on the blocks and heads to tell what chamber size etc etc.
Ka or J or C casting heads for example 400-425 or 455 notice they are letters and the smaller engines began with a number those small engines would be a 260-307-350 or 403.
Yes a 403.
Big bore and short stroke.

 

[swampratt]

But wait the sb2 is a sbc and here is the valve cover.

And here is an SB2 head.

You will probably never see one of these in a wrecking yard though.
Nascar stuff here

 

[red442joe]

Sb2 is sb2....

Joe