Someone told me in a previous post that running a 1 inch 4 hole carb spacer with an RPM Air Gap manifold was not a good idea and isn't recommended. I always thought that the 4 hole spacer was supposed to increase plenum chamber volume, and allow for a better metering signal to the carb. It is also supposed to help produce better low to mid range torque production. However, if it is not a good idea to use this spacer, I can take it off and that will help take some overall height off of my induction system. I am running the Air Gap manifold with the 1 inch spacer, the 14x5 K&N filter with a 1.5 drop base and a K&N substack. Thanks in advance for any replies to this thread, Paul Moore

Spacers are funny things. Sometimes they do exactly what you expect them to do. Sometimes the do the opposite. My rule of thumb with spacers is this: put one on and make some runs. If you go faster, keep it. If you go slower, take it back off.

From all the manifold test's that I have read, including David Vizard's books, the only thing to avoid is an OPEN spacer with an RPM manifold ( Airgap or regular ). You will lose Torque ( as expected, but HP also apparently drops..

A 4 hole is fine ( I have been running one for years ) and will give you the benefits as you noted. The main advantage to the 1 inch four hole is that it gives the fuel\air mixture more distance and time to " Turn the corner" before hitting the plenum floor. The upper plenum floor is the big challenge.

An " open " spacer on a Dual Plane manifold often screws up the fuel distribution and tuning effects of the Dual Plane design.

You combo is good.

Elegant and simple...good advice.