Phenolic Spacer
 

I am going to take off the upper intake to fix a coolant leak sometime in the future. I was wondering if it would be a good idea to add a spacer and if so which brand? How much power do they usually make? Thanks guys (and girls)!

Later

you probably won't see any gain in power (that you can feel anyway)

what it will do is basically lengthen your runners and raise your powerband a little, so you'll be making the power a little bit higher in the RPM range. It will also help keep the upper intake cooler because there isn't a metal on metal contact between the upper and lower intakes. This will help add a little power but not a whole lot.

I'd wait till you got an aftermarket intake and get one for that.

also if you go more than about 3/8 - 1/2 " then your intake will rub your hood (unless you have a cowl)

I've got a 1/2" spacer and it just touches the underhood felt lining - no dent in the hood though! :D

I got the spacer because my FMS valve covers were hiting the bottom of my GT-40 intake.

E

Actually lengthing the intake with a spacer will lower the point where resonant tuning occurs in the manifold, bumping up torque and trimming off some HP.

However the insulating effect might be enough to maintain higher RPM power. Ideally your torque would be bumped up and there would be gains at all points in the rpm range due to the cooler manifold.