Intake Manifold Designs

[AlwaysBroke]

I have been looking into creating a custom intake manifold for my Chevy 4.3L and I found a really good link explaining the different types of manifold designs, with pros/cons and some calculations.

http://victorylibrary.com/mopar/intake-tech-c.htm

Its all relating to V8 motors but good info non the less.

 

Also, with intake runner lengths a good calculation is:

 

N x L = 84,000

 

where N represents the desired engine rpm to tune for, L is the length in inches from the opening of the runner tube to the valve head, and 84,000 is a constant. Just use algebra to find the factor that you are looking for.

 

Hope this helps someone as it has me

[jc052685]

Would you not need to also know runner diameter to properly calculate neede length??

[AlwaysBroke]

The way I understand it is that you calculate the length based on what RPM you desire peak torque. And then you want the smallest cross sectional area that you can get without loosing horsepower. How large the area is depends on the displacement of the motor and how long the runner is.

However in looking deeper into this I'm reading many theories about this, and alot of them contradict each other. One is that you want the diameter of the runner to be 80-90% the size of your intake valve.

 

Does anyone else have a better understanding, or maybe experience with this?

[gjc5500]

That is pretty much what you hear when you are at UTI so im gonna say YUP. lol.

 

yea thats right about runner length.