Big Block vs Small Block??? differences..help please

[SilverFox90]

i know that i am probably going to sound like some 15yr old kid who knows nothing about cars, but i have to ask....i have been around cars and worked on them for a while and consider myself to have pretty good automotive knowledge...but one thing eludes me and no one has given me a good answer...what are the physical differences between a big block and small block..i know what kind of power, torque, diff etc but i really dont know the real definition of a big block or what physically makes it diff from a small block....thanks for any help

 

[Look Its Aaron]

The block is physically bigger than a small block.

 

[bluevenom867]

Yeah like, Look Its Aaron, said it is about the out-side physical size not displacment.A ford 351M is a big-block even though it has the same displacment as the 351W which is a small-block.
Good ex. of a small big block:
Mopar 318 wide block.Thous things are huge but they only have 318 cubes?

 

[SilverFox90]

yeah i knew it had nothing to do with displacement, so the only diff is the actual size of the block?...then why is it that most big blocks develop higher torque and are usually made to wrap less rpms than a small block...?

 

[bluevenom867]

That is because MOST big blocks ARE bigger in displacment.

 

[NeVeRLiFt]

yeah i knew it had nothing to do with displacement, so the only diff is the actual size of the block?...then why is it that most big blocks develop higher torque and are usually made to wrap less rpms than a small block...?

Big blocks have longer strokes. This increases their displacement and helps them make more torque. I have always ended up making almost every big block I have had knock (400, 455 Pontiac, 455 Olds, and a 390, 460 Ford)
They dont like being spinned over 5k rpm most times.

On a side note I have never blown a 302 Ford or a 403 Olds
Trust I have tried.

When racing a big block you will usually see them walk like a mofo in 2nd gear and top end. Most small blocks can jump them out the hole or hang with them... but by the end of 2nd gear the big block will walk off.

Besides the big block having different size for the motor making it bigger and the longer stronger and large bore... almost all big blocks have great heads!

I'm talking large valves and intake and exhaust ports. On most small block motors you can stick say 3 fingers in the intake port for example. With big block heads you can stick your whole hand in some!

Good examples are the 428, 429, 460 CJ heads and the 351 Cleveland 4v head, all these from Ford have bad ass heads with huge ports and flow like crazy.

The Chevy 396/427/454 have huge ports!!!

Buick has the monster 455 and plus the block itself is very light weight for a big block.

Pontiac has the Ram Air IV heads

And Mopar has the Hemi heads and their wedge heads.


Most people dont realize that the old boss 302 motors use the 351 Cleveland 4v heads with a special intake

 

[SilverFox90]

works for me thanks for the info guys now i have filled another gap in my automotive knowledge...one more ? by the block bein bigger does that mean the cylinder walls are thicker allowing it to be bored over more?....if they are then that would make sense as to why big blocks can be stroked and bored to be so much more CI than small blocks....thanks again bluevenom867 and aaron

 

[65ShelbyClone]

one more ? by the block bein bigger does that mean the cylinder walls are thicker allowing it to be bored over more?....if they are then that would make sense as to why big blocks can be stroked and bored to be so much more CI than small blocks....thanks again bluevenom867 and aaron

No, this is entirely dependent on the block design. Take a Ford 427 FE for example. On a good day the most you can safely overbore is .030. You'd think they had paper tubes for cylinders. Most rebuilt 427 blocks are sleeved. As far as more displacemementpossible, I cant think of the scientific reason, but I think it has to do with geometry and maybe trig.

 

[NeVeRLiFt]

works for me thanks for the info guys now i have filled another gap in my automotive knowledge...one more ? by the block bein bigger does that mean the cylinder walls are thicker allowing it to be bored over more?....if they are then that would make sense as to why big blocks can be stroked and bored to be so much more CI than small blocks....thanks again bluevenom867 and aaron

At one time the Olds 403 had the biggest bore size of any production motor and with its small stroke made for a good motor.

Most motors can take .30 bore and you should always check the walls before going any more. .60 is usually the max. Most stock blocks I have saw that are bored more than .60 run hotter than normal and can be a bitch to keep cool in the summer. You can always get a Chilton manual are look up the info on the block your interested in have fun!

 

[SilverFox90]

thanks again