Editing Intake manifold (section)
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==Carb spacers== Carb spacers in their various designs are often used as a tuning aid and for helping to make power in the range where it's needed. ===Open spacer=== Tend to boost output in the upper range and will increase plenum volume. On an intake like the Edelbrock RPM (non Air Gap) dual plane intake, using an open 1" spacer will let the intake make identical power to the cut down plenum divider of the Air Gap. ===Divided spacer=== These will retain the dual plenum low-to-midrange benefits while possibly raising the power peak. Tends to make the runners seem longer. [[File:CARB SPACERS WOOD Q-JET 001.jpg|thumb|300px|left|Pair of homemade spacers.]] [[File:CARB SPACERS WOOD Q-JET single.jpg|thumb|300px|left|Spacer made specifically to fit the Pontiac Performer intake. Spacer is upside down.]] <br style="clear:both"/> ===Notched plenum divider vs. spacer vs. single plane=== The 1" x 3" notched plenum divider of the RPM AG falls in between an intact plenum divider of a dual plane and an open spacer on a dual plane. It allows ''some'' of the benefits of a single plane, but w/o all of the downsides. It has been observed that using an Edelbrock C3B- with its cut out for the secondary throttle blade of the Holley 3 barrel extended out to a little over 3.5"- it performs right in between an open spacer and no spacer or "notched" divider of a dual plane. This also seems to be the trend w/the Edelbrock RPM vs. RPM Air Gap. An unmodified C3B is shown below, left. An RPM AG below, right. [[file:CB3_003.jpg|400px|left]][[file:Rpm_7501_air-gap.jpg|400px|right]] <br style="clear:both"/> An open spacer on a dual plane will increase plenum volume- something that a notched plenum doesn't do, and this is part of the reason why an open spacer/dual plane often falls in between an open plenum and a standard dual plane without an open spacer in performance. Also there's no added carb height when using a notched plenum divider like there is using a spacer. The added height of the spacer can help allow the air/fuel to make the turn into the runners with less deflection of the A/F stream when it hits the plenum floor at high rpm. ===Also see:=== *[http://www.hotrodders.com/forum/carb-spacer-163755.html Carb spacer] thread on Hotrodders forum. *[http://cms.nhra.com/dragster/1999/issue05/racing_technology.html Racing Technology Tuning with carburetor spacers] from NHRA.com * Here's a dyno flog by Car Craft involving 23 different intake manifolds..... *[http://www.carcraft.com/techarticles/1309_dual_plane_intake_manifold_comparisons/viewall.html]
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