Velocity Stacks Options

[neyen14]

I am using dual Weber 40 IDF's. 96mm cylinders c35 scat cam

#1 The Original "velocity stack" is a straight shot down the throat of the carb.

#2 Shorter shinier velocity stack is for 40 - 48 IDF and leaves about a 1/8" lip at the top plate of the carb

#3 The taller less shiny velocity stack says it is for DRLA & IDF 36 - 40mm but leaves about a 1/16" lip at the top plate of the carb

I started to widen the inside of the #1 Original and thought it better to have a straight shot down the throat then it would be to have any bit of a lip.... however, I was recommended to use the non original velocity stacks and don't worry about the lip, they've "found it doesn't affect performance".... which seems counterintuitive to the ideas of porting, polishing, and general flow etc

1. Do you think opening up the original velocity stack and having the straight shot is worth it?

2. Should I not worry about the lip?

3. Is there a stack that would fit the 40 IDF specifically without covering a range?

[neyen14]

Here's an above view with each

[Jamie]

Here's an above view with each

The flow dynamics of velocity stacks goal is to create a straight column of air induction into the carb throat without interruption. Any deviation of the straight induction usually creates turbulence, and that reduces input flow. For a full on high RPM race engine that disruption might be significant, but for a street engine the reduction of intake air flow would not likely be notable. The design of an air cleaner for the intakes would be of concern, as any restriction there would be of more relevant for race engines with greater intake air flow requirements, less so for a lower RPM street engine. (IMG:style_emoticons/default/driving.gif)