what are the advantages and disadvantages of using a carb spacer?

 

"Raising the powerband" is the traditional reasoning, may also help remove it from heat source a bit? As I'm not a carb guy I'll leave it at that.

 

The most common type of spacer is the open type, but there's also the kind with four holes. By adding the open type you're effectively increasing the plenum volume which will, as previously stated, raise your power band with a loss at the lower rpm's. The four hole spacer acts like an extension to each barrel of the carb, which helps maintain the velocity and improve throttle response.

 

if im running an edelbrock RPM air gap then i would want to run the spacer with the four holes in right?

 

You might want to look at these too. These are great spacers for Oval Track cars and street cars.

http://www.wilsonmanifolds.com/tape4hole.htm

 

It depends on what your looking for performance wise and in what part of the rpm band you spend a lot of time in. The edelbrock rpm air gap is a dual plane manifold, so if you add the four hole spacer you might choke your engine a little at the top end. But this might not be too bad a thing if all you do is drive it on the street. It's hard to say because it really hinges on your application and what your desires are. The thing you could do is try out a few types and sizes and see what suits you/what works.

 

That's true but a good spacer will add CFM to the carb and that should always help.

Finding the right combo is the best way to go.

Bret

 

One thing that's been missed here. A carb spacer is most beneficial in the fact that it allows the inlet charge a greater distance (throttle bore to plenum floor) in which to makes it's turn. More of an airflow "quality" issue than anything else. Spacers of the 4-hole variety can compound this problem as they create higher inlet entry velocities. Some designs are better than others.

Take care