Convinced I could do better, I removed the K&N pods (dirty, nasty little things) from the throttle bodies on my 1200 Sport and replaced them with filtered velocity stacks. Trial and error led to a solution that I am very happy with. And they look good too! Shame they’re covered up.
The approach was to create a velocity stack for each throttle body, same length as the original (4.5 inches), with adequate filtration without using a pod filter. This was achieved using silicone hose to join a velocity stack to each throttle body, a triple-layer screen on the end of each velocity stack, and a pre-filter over each screen.
Parts used, and their sources are as follows.
The approach was to create a velocity stack for each throttle body, same length as the original (4.5 inches), with adequate filtration without using a pod filter. This was achieved using silicone hose to join a velocity stack to each throttle body, a triple-layer screen on the end of each velocity stack, and a pre-filter over each screen.
Parts used, and their sources are as follows.
- Aluminum velocity stacks (x2), 1.97 inch ID, 3 inches tall (part nbr PJM-VS-4) from PJMotorsports.com.
- Red silicone hose (1 foot), 2 inch ID, and lined hose clamp (x4), 1.81 to 2.75 inch ID (part nbr 3613-2.75) from PegasusAutoRacing.com.
- Air horn screens 70 mm weber intake 48/51 ID (part nbr 16627) from RacingBeat.com.
- Velocity stack 3.5 inch pre-filter (part nbr F192) from Filterwears.com.
- Measure and cut sections of silicone hose such that you have a total length of 4.5 inches when each is clamped to a velocity stack. An effective method of cutting the silicone hose is to snug a hose clamp onto the hose against the line to be cut, and then cut along the clamp using a very sharp utility knife, preferably with a new blade. Clamp the silicone hose sections to the velocity stacks.
- Snug a clamp onto the throttle body end of each silicone hose section. Loose enough such that each section will fit onto a throttle body, and tight enough that it stays in position for final assembly. And position the tightening screw such that it is accessible when placed on the throttle body.
- Fit the screens to the end of each velocity stack.
- Fit the pre-filters over each screen. You now have two velocity stack assemblies ready for final installation.
- Clamp each assembly to a throttle body – right one first, then the left. I used a little silicone on the inside edge of each hose to aid in slipping each assembly onto the throttle body.