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

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Snattlerake

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

EX:

Small block
1718419164524.png

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


Big block

1718419270076.png


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

JH47

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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

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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
 

swampratt

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

Big block valve cover.
1719356245112.png


And here is a SBC cover.

1719356291469.png


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

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But wait the sb2 is a sbc and here is the valve cover.
1719356865089.png
And here is an SB2 head.
1719356909389.png

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

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