Ok, I have no idea if this is a worth while upgrade, or if it makes a difference which product I use, so I'd like to tap into everyone's collective wisdom here. I was thinking of adding an aluminum 1" carb spacer (instead of the tiny stainless steel spacer currently in place) from Summit Racing to my '66 Skylark's 300 4bbl intake. Supposedly, I can get better low-end torque if I use one of these spacers between my AFB and the manifold. So, my questions are: 1) is it true, will my low-end torque increase after adding such a spacer; 2) Is there a difference in using an open plenum, square bore versus a 4 hole, square bore design; and 3) is there a certain product any of you can recommend for such an application (I see products available from Mr. Gasket and TD Performance, among others)? Thanks.
Carb spacers The arb spacers are very beneficial. I am currently running a stock 350 with the cast iron intake and Edelbrock 600 carb. I put the 4 hole alumn spacer to keep the plenum to plenum going. If you use the open type. You may develop a slight bog when you first hit full throttle. I have run into this on a few other combinations. This alumn spacer is about 1/2 inch. At my home racetrack, sometimes they run us back to back and I added a Moroso phenolic 1/2 inch spacer, also keeping the 4 hole plenum going. This added a very noticible difference in low end torque with the one inch total spacing. Hope this helps!
There are spacers, and there are spacers. One benefit of using a spacer, in a non-thermally conducting material (Plastic, or phenolic. Aluminum has good heat transfer properties, exactly what you do not want.) is to isolate the carb from manifold heat, = more power. (On the strip.) A 4-hole spacer, will act to enhance the torque producing characteristics of the manifold, whereas any spacer that significantly increases the intake plenum volume, and opens one bank of the manifold to the next, (An open spacer.) will tend to shift the torque peak to a higher rpm. It really boils down to what you want the end result to be. More top-end? Go for the 1" (Or taller) open spacer. Lacking bottom end torque? Go for the 4-hole type spacer. As a 300 incher lacks in torque, I would suggest the 4-holer, in a heat insulating material, starting at 1" Make sure you feed the carb good clean, COLD air. Every 10 dergees F. drop in inlet temperature = 1% increase in horsepower. (If jetted properly.) The taller the spacer, you may need to increase the accelerator pump shot, as the increased manifold volume may make the carb sag a bit on sudden accel. IMO. Regards, Robin Sipe.
Using a half inch, open design, wood spacer on mine. Open design increases plenum volume resulting less low-end torque but more top end power. Wood eliminates most heat transfer and makes most car show goers ask "Is that really wood?"
When I put an Edelbrock 600 cfm carb on my 340, I had to use a 1" spacer to allow the carb's shift kickdown pivot to clear a casting boss on the intake manifold. Haven't noticed any problems; engine runs strong.
