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Thu Feb 04, 2010 11:39 am

CB sells some stacks that are 1'' tall. I need some short ones to clear unifilters i have. Will they still serve their purpose being that short?

Fri Feb 05, 2010 2:34 am

Velocity stacks serve a couple purposes.

1. Funnel the air in. The air no longer has to turn a 90° corner which costs energy that could otherwise be used to draw in more fuel/air.

2. Contain fuel stand-off. The bigger the cam the more valve overlap and therefore the more stand-off. That's why you see the BIG stacks on the drag racers with the 51.5 IDA's.

So, you know your combo. Would you benefit? You would at least from point #1.

Fri Feb 05, 2010 5:20 am

I don't mean to Bogart your post here, but I am installing a set of original height velocity stacks on my 44IDF's right now and the damned studs aren't tall enough for the filter base plate and velocity stacks from CB Performance. Anyone else ever ran into this? I'm having to file down the base of my stacks in order to make them clear. Kind of frustrating on brand new parts to mess them up like that.

Fri Feb 05, 2010 6:22 am

I had to back the studs out of the carb so they would be long enough.

Fri Feb 05, 2010 6:57 am

chambersc wrote: I don't mean to Bogart your post here, but I am installing a set of original height velocity stacks on my 44IDF's right now and the damned studs aren't tall enough for the filter base plate and velocity stacks from CB Performance. Anyone else ever ran into this? I'm having to file down the base of my stacks in order to make them clear. Kind of frustrating on brand new parts to mess them up like that.

Get longer studs....

http://www.nutsandbolts.com/stud-index-metric-sae-uss-metric-studs-c-30_131_132.html

OR some similar place...

Dale

Fri Feb 05, 2010 7:10 am

Velocity stacks are not there to look pretty. If you have two engines drawing exactly the same amount of air, by changing the stacks height and shape you can increase the speed at which the air enters the carbs. Thus having a different effect on each engine. Short is usually good for quick response, tall are more for long runs at higher speeds which usually give better mileage.

The air at the mouth of the stack is compressed as it gets to the restricted area and picks up Velocity as it enters the carb. Without the stacks the air would be in chaos at the top of the carb.