I've herd a lot about putting a spacer between the upper and lower intake. I'm in a CNC class so i can make it myself, plus it makes a good project, but equally important i want to know if it'll do good, or harm me more then anything. anyone have one/use one? also what thickness is good?
Dunno, but CNC....im getting my Degree in Computer Aided Manufacturing and Design...good Idea, I think the spacers help cool the intakes flow though..
-Nick
It may help by providing extra room between the upper manifold and the rocker covers. The extra space may allow you to remove the rocker covers without having to remove the upper manifold.
The real intent is to use a material that does not conduct heat, like hardwood or phenolic plastic. This keeps the upper manifold cooler since it doesn't pick up heat by conduction from the lower manifold.
For some cars, adding an extra inch to the intake path improves low end torque. The effect would to be to shift the torque curve downward a bit. It would have to be 1" or thicker to have any measureable effect.
The spacers are used primarily for 2 reasons - one is simply to create more room tall valve covers. The valve covers are often needed to clear certain rocker arms/valve trains. Second is to thermally isolate the upper from the lower - making it possible to more easily ice down the upper intake between rounds which theoretically keeps the manifold from heating up the air intake charge as much as it otherwise would - which helps power. To perform this function, the spacers are made out of some composite, non-metallic material - usually reinforced phenolic resins. The spacer also lengthens the manifold runner length which, again theoretically, shifts the power curve slightly - all things equal, a longer runner makes a bit more torque lower, a bit less power.
As a practical matter, most people don't notice any difference at all except that their manifold/throttle body clears their valve covers. But it's a good CNC project provided you use the right material.