I was always under the impression that by increasing the length of your intake manifold you decreased your lowend torque. I.e. if I put a 2" spacer under my carb, i'd lose low end power.

But in reading up at the rotaryshack, they said this about their 1-piece sidedraft intake manifold:

"the long manifold delivers unsurpassed torque improvement over the original setup also."

So if I used aluminum or phenolic spacers under the carb, would I kill my lowend power or help it out?

 

Longer runners typically help low end torque at the expense of high end power.

 

..and vice versa