I am building a vintage race 71.
Almost stock 2.0L with dual 40 IDF webers.

I have both manifolds- Short & Long:



What are the pros & cons for each? I assume my throttle linkage would be different for the two...

The short would give more space in the engine compartment.

Stu

They affect the length of the intake manifold, and thus the tuning (supposedly changing the torque values at different rpms). For a street car, there should not be a lot of noticable differance.

With a crossbar style linkage, there should be no real difference in the linkage except perhaps the attachment of the throttle cable sleeve position.

It varies with the combination of injection/carburetor, cam, heads, exhaust, etc, but generally short manifolds need high RPM to give higher horsepower, long manifolds give more torque at lower RPM's. For a (non-race) street car you're generally better off with the long manifolds.

You would see a differance if you compared them on a dyno but on a street car, not so much.

On a 6cylinder small bore motor with big cams (ie: S camshafts) They use the tall manifolds on purpose to help combat reversion.

on a 4 though that is not an issue.
make sure you also use phenolic blocks.
mandatory at our altitude and cooling with current fuels.
(even the race fuel will want the phenolic blocks)

brant

without the phenolic blocks i could hear and see the fuel boiling in my emulsion tube wells. after shut down.

Plenum effect with the tall tubes. On a higher displacement engine, such as a 5.7L v8, I ran a tall tunnel ram at the track. It ran better on the street with the low rise manifold.
I would go with the tall manifolds on track.

I disagree. For a street car, the longer intakes should give you a bit more low end torque, which is preferred over high end rpm torque and hp. On a track car, the reverse is usually true.