intake runner diameter

[Anonymous]

Ive been doing some research and have some questions, you guys seem to have a ton of knowledge so I thought Id ask here on this forum. First example: stock engine, what would give the best power, large intake runners for more airflow or smaller runners for more velocity? And what about on a modified motor? I always hear that both give more power, I have read that smaller runners are good for low end which makes me think that would be better for a stock motor without a big cam. I assume there is some sort of give and take with this and that there is a "sweet spot" for the size, but how would you figure out how big to make the runners? Thanks!

 

[Thad]

Read somewhere that the optimum runner ID for street performance was the same as the intake valve OD.

Opinions? Other Data?

 

[XPC66]

The problem you will have is that after someone has spent money making a set of runners, they are hardly likely to say they aren't the correct size. Generally though the shorter the runner the higher the revs before the "sweet spot". The diameter will be limited by the port size, the port size by the valve curtain area, the valve curtain area by the lift & combustion roof, etc.

 

[Anonymous]

If you get pipemax it will allow you to calculate the optimum length and diameter of the intake and exhaust. Good price also