My kit came with the Weber/Redline air filters but no velocity stacks. Does anyone have a good source for 40 IDF velocity stacks which will fit inside of the air filters? Will adding a short (est. 2" stack) inside the filter element make a real difference?

CB performance

aircooled.net

Thank you for the recommended vendors. Do you believe that the stacks will add performance/increased drivability to the car?

There was a thread a few years back that did a test on a dyno testing what affect changing the VS made to top end and bottom end power! I don't remember what the final out come was but it did make for an interesting read!!

Found it!!

Velocity Stack Testing by Jake

I just took a closer look at the thread and it looks like the graph and photo links are no good any more! Maybe Jake could update his results here?

CB Performance are crooks when it comes to shipping costs. I'd go with aircooled.net.

You must have v.s. on the carbs.

My set from redline is also Velocity stackless, how vital are they?

I bought some from a local VW bug shop. A 0 on the hassle scale.

The air entering the carb is quite turbulent. Stacks smooth out the flow which results in an increase in velocity. More velocity = a denser air fuel mixture. Think forced induction on the cheap (it's no turbo or blower but it helps). It also cleans up the vacuum signal to the mains. They aren't vital but you will have some gains up top.

off to the VW shop when I get a chance then!

Tell these guys they are not "vital" or that lenght is not important.

Apples and oranges. In a race car, where a few HP makes all the difference, they are "vital" to winning. Parked in my driveway that would be a squirrels wet dream. An aircleaner is more "vital" than a mm of stack height in a street car.

with 40 IDF carbs on a slow velocity type 4 head, the short (1/2 inch tall) velocity stack that is built into the air cleaner base seems to be the right setup.

Jake did quite a bit of testing on the proper heights to use and it certainly has alot to do with the camshaft and head setup you are running.
Anything close to stock (heads, valves or camshaft) will actually experience a loss of power in the lower RPM range if the taller stacks are installed.

As you add height (on the type4 motor) it moves the HP up in the rpm range and this is a high torque motor down low.

Hard question to answer without knowing your specific setup and your intended use of the car.


Rich

+1 .......... I like graphs of 'real life' tests ........