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Discussion Starter #1
Why is it that a Big Block uses a much larger head then a stroked small block?

For example, I've been told my 408 sbf (forced ind) would like a set of 225 / 245 high ports and my buddies 406 bbc (nitrous) uses 290cc edelbrocks.

I'm sure there's more then just comparing cubic inches but I don't know enough to answer this question.

Any thoughts?
 

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doesnt matter what engine, it works the same, its about cubes and rpm which = cross section area needed.
 

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Discussion Starter #5
Is there a clear explanation of "cross section" out there? I've searched here but haven't come up with anything simple.
 

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It comes down to inexperience and money. The proper head for a 400 plus c.i.d small block is not your average $1500.00 Summit or Jegs special. Then you have the velocity people that are stuck in 1980's, which anything bigger than a 200 cc intake port is 10,000 rpm full race territory.
 

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Dr. Greenthumb
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It comes down to inexperience and money. The proper head for a 400 plus c.i.d small block is not your average $1500.00 Summit or Jegs special. Then you have the velocity people that are stuck in 1980's, which anything bigger than a 200 cc intake port is 10,000 rpm full race territory.
This is TOO true. I remember when I first started out. The tech guys at places like Summit would tell me a set such and such were way too big for my daily street driven car. It wouldnt make any low end torque with such big heads. Then few years later LS1's come out flowing more on bone stock cars. lol
 

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........because Sportsman II's didn't flow very much for bein' a 200cc runner (230-250cfm? @ peak) I bought a set back in the day, thought I was livin' in "Race Head" territory now! Sheesh. There's some merit to the velocity side of things, depends on your poison.
It's about "application". Forced Induction engines obviously don't depend on atmospheric pressure to fill the cylinders the way a N/A or Nitrous build does, so velocity is less of a concern. You can get away with a much bigger head nowadays because the heads (and cams) are so much better, not because the knuckledragger "Bigger is Better" guys were "right all along".

Think about it.


---==Temio Williams
Yuba City, CA
 
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