69 camaro 350.. .30 over world s/r heads, zz4 dual plane intake cc 268xe cam, all the msd stuff, 670 avenger carb. sreet car but love to play...will i benifit at all form a carb spacer..if so what kind and which one.....i had one before but didnt know if it served that big of a pupose....

How tall of a spacer are we talking. With a 1/2" spacer you may see a minor improvement, but right now it looks as though you have a pretty well matched set up. I think a taller carb spacer would raise the power band out of balance with the rest your set up. This will help build power up top at the cost of some low rpm torque. The other question is hood clearance?

I have commented on this before (suggested cutting a notch in the manifold plenum wall). A carb spacer increases plenum volume and acts as though you have increased your carb size (cfm not jet size). If you are experimenting there are many heights and two styles (one hole or four) to choose from. The four hole variety doesn't sacrifice as much torque, but doesn't add as much to peak horse power as the one hole.

For street driving you want as much area under the torque curve as you can get (tall and flat). For all out racing you want max horse power and gear the car to stay within the power band (which is why race cars don't do well on the street).

Right now have good heads and a hotter cam than the stock engine, and an increase in manifold efficiency would probably help raise both your torque curve and peak horse power. The ZZ4 manifold is equivalent to the Edelbrock Performer manifold (that is who makes it for GM). I like Edelbrock's Air Gap RPM manifold, though it no longer looks as stock, it gives better performance than the single plane to about 5600. The only other down side could be clearance.

Larger Dave

On a dual plane a 1in open spacer can help the upper rpm torque and power. I wouldn't use a 4hole with your combo a dual plane and a 4hole spacer works very well on a torque motor.