Air intake plenum runner lengths

[zentac]

Anyone know the total length of the intake plenum runners (top and bottom plenum)

Im looking at getting a new plenum made and

Long Port Length: Improve low RPM range
Short Port Length: Improve high RPM range

so Im thinking I need a shorter set of runners, but dont know what the current length is.

Anyone got one in pieces that they could measure?

I really need from the valve to the top of the plenum runners.

[zentac]

based on the formula's Ive seen for calculating this I would say the intakes are between 17-18 inches long. Be interesting to see how close I am

[scott.mohekey]

I've never measured them but agree with your expected figures.

[mpau009]

Iv had a rough measure just now with a piece of wire and my spare manifolds.

I didnt know exactly what i should be measuring to, but if you look at them side on 'banana style' measurements,

The lower manifold is

Short Radius, runner length, 96mm
Long Radius, runner length, 115mm

Upper Manifold from the base to the part where the runner joins the main plenum piece,

Short Radius, runner length, 220mm
Long Radius, runner length, 320mm

Does that help at all?

[zentac]

Im not exactly sure either, but if we take the middle of those values as is we were measuring the middle of the plenum we would get 376mm / 25.4 = 14.8 inch

Any idea who much there is in the head before you hit the valve?